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this file - ICOM-CC

ICOM-CC Enamel Group
of the Glass & Ceramics and Metals Working Groups
3rd Biennial
Experts’ Meeting on Enamel on Metal Conservation
October 8 & 9, 2010
The Frick Collection – New York City
Extended Abstracts
ICOM-CC Enamel Group
of the Glass & Ceramics and Metals Working Groups
Experts’ Meeting on Enamel on Metal Conservation
2010
Conference Chair and Enamel Group Coordinator
Agnès Gall Ortlik
Local Organizer and Editor
Julia Day
This is a non-juried publication. The papers presented at the meeting are selected
by the coordinator and local organizer. Authors are responsible for the content
and accuracy of their submissions and for the methods and materials they present.
The following papers were edited by the local organizer and represent the
research presented at the Experts’ Meeting on Enamel on Metal Conservation, at
The Frick Collection, New York City, October 8 and 9, 2010. The papers are
listed by program session topic and in order of the presentation.
Cover image:
Detail, Plaque: The Adoration of the Shepherds, 1555–1585
Jean de Court (Master I.C.) (c. 1555–1585)
enamel on copper
13 3/8” (33.97 cm)
Henry Clay Frick Bequest, 1916.4.34
The Frick Collection
1
PREFACE & ACKNOWLEDGMENTS
5
SCIENTIFIC ANALYSIS
Authentication of Limoges Enamels by Noninvasive Techniques: The Larcade Collection
Angelo Agostino, Maurizio Aceto and Simonetta Castronovo
17
24
On-site Analysis of Enamels on Metal from the Fifteenth to the Nineteenth Century: An
Attempt Toward Differentiation between Genuine Artifacts and Copies
Burcu Kırmızı and Philippe Colomban
PRESERVATION & TREATMENT
Reviewing the Conservation of Unstable Enamels at the Victoria & Albert Museum
Juanita Navarro
30
Reversibility and Compatibility of Restoration Materials for Painted Enamels
Béatrice Beillard
37
Conception and Making of a “Display Box” Adapted to the Conservation of Two Painted
Enamels of the Louvre
Françoise Barbe
42
Preventive Conservation of Limoges Enamels
David Thickett and Jenny Studer
49
Working on a Large Scale: Considerations for the Conservation of an Outdoor Enamel
Mural
Cátia Viegas Wesolowska
55
A Concise Bibliography on the Technology, Deterioration, and Conservation of Enamels
on Metal
Agnès Gall Ortlik
59
HISTORY & TECHNOLOGY
Japanese Cloisonné Enameling on Glass Substrate, from the Late Nineteenth Century to
the Present
Fredric T. Schneider
71
Footed Bowl or Only a Bowl? The Investigation of a Seventeenth-Century Limoges
Painted Enamel Object
Birgit Schwahn
83
An Examination of a Fourteenth-Century Basse-Taille Enamel Diptych from Cologne: Is
It Fourteenth Century and Is It from Cologne?
Diana Johnson Galante
89
Jewelry or Sculpture? The Limoges Medieval Virgins Made of Copper and Enamel
Véronique Notin
97
Concerning a Mysterious Limoges Enamel Group of the Passion after Dürer
Isabelle Biron and Monique Blanc
PREFACE
The Enamel Group was established in 2006 to fill a need within the two Working Groups of the
ICOM-CC, Glass & Ceramics and Metals, and to facilitate an exchange of information among
experts who specialize in either glass or metals. The combination of these two materials poses
specific conservation issues, which are not often addressed at the general meetings; therefore the
Experts’ Meeting on Enamel on Metal Conservation was developed.
The first meeting of the Enamel Group was held in 2006 and was supported by EU COST
program at the Château de Germolles. The second meeting was held in 2008 and was supported
by the Académie de France à Rome in the Villa Medici. The last two meetings were very
successful, with more than eighty conservators, curators, and scientists attending the 2008
meeting. Professor Dr. Gerhard Eggert, from the Objects Conservation Program at the State
Academy of Art and Design in Stuttgart, acted as the coordinator of the Enamel Group, and was
followed by Agnès Gall Ortlik, a private conservator of enamels based in Barcelona, Spain, who
is the current coordinator of the Group.
The 2010 meeting is a two-day event, consisting of a day and a half of lectures, including
a panel discussion, and a half-day to visit related enamel collections in New York. Two posters
will also be presented. The event is coordinated by The Frick Collection’s assistant conservator,
Julia Day and the ICOM-CC Enamel Group coordinator, Agnès Gall Ortlik. The lectures cover
issues related to the preservation of enamels, new scientific research, and technical, and art
historical studies. The panel discussion features experts who will discuss issues related to the
conservation and analysis of enamels. The results from this discussion will be reviewed at the
close of the meeting and create a foundation for current methodology in these areas. Speakers are
from France, Italy, Poland, Spain, Turkey, the United Kingdom, and the United States.
1
ACKNOWLEDGMENTS
The Enamel Group would like to thank, Anne Poulet, Director, The Frick Collection, for
generously agreeing to host this event. In addition, we would also like to thank those at the Frick
Collection who helped make this event possible: Colin B. Bailey, Robert Goldsmith, Joseph
Godla, Denise Allen, Charlotte Vignon, Joanna Sheers, Rosayn Anderson, Elaine Koss, Julie
DiFilippo, William Trachet, Adrian Anderson, Rosalie MacGowan, Alison Hillier, Sean Troxell,
Heidi Rosenau, Helen Freeman, Adrienne Lei, and Lisa Foerster. This event would not have
been possible without the additional support from the Security, Engineering, and Housekeeping
departments, as well as the volunteers, Helen Garvis, Ann Tartsinis, Susan Billy, Elizabeth
White-Pultz, Tereze Gluck, Ophelia Webber, and Raanan Einav. Special thanks is also extended
to the panel participants, Béatrice Beillard, Pete Dandridge, Terry Drayman-Weisser, and
Hannelore Roemich, and to Juanita Navarro for proposing the format for the discussion. In
addition, we would like to express our gratitude to Cátia Viegas Wesolowska, assistant
coordinator of the Enamel Group, and especially Lisa Pilosi, Christian Degrigny, and Gerhard
Eggert for their efforts in establishing the Enamel Group as part of the Glass & Ceramics and
Metals Working Groups of ICOM-CC.
Julia Day and Agnès Gall Ortlik
2
3
4
AUTHENTICATION OF LIMOGES ENAMELS BY NONINVASIVE TECHNIQUES:
THE LARCADE COLLECTION
ANGELO AGOSTINO, MAURIZIO ACETO, AND SIMONETTA CASTRONOVO
ABSTRACT – Medieval Limoges enameled jewelry are valuable objects to collect, and led to a
proliferation of copies in more recent times which are now widely dispersed in collections all
over the world. It is sometimes difficult to identify originals through a stylistic approach;
therefore a systematic methodology based on noninvasive analytical techniques was proposed to
distinguish between medieval and modern enamels. This work focused on the medallions in the
Larcade Collection at the Musée du Louvre in Paris. Analysis was carried out using ultraviolet
and visible reflectance spectrophotometry with optical fibers, as well as X-ray fluorescence
spectroscopy to obtain elemental composition. Multivariate analysis was also used to compare
this data with that obtained on enamels from the Piedmont area.
INTRODUCTION
Until recently, X-ray fluorescence spectroscopy (XRF) was used as a preliminary technique for
the study of glass, giving qualitative information only, which was often approximate and
incomplete. This was because of the well-known problems concerning light matrix (glass)
examination and the impossibility of detecting important elements such as sodium and
magnesium. Recent developments in this technique (Longoni and Fiorini 2006) and the effective
noninvasive approach, allowed quantitative results to be obtained on a number of Limoges
jewelry pieces in the Piedmont area. Byzantine Limoges jewelry, developed between the twelfth and the fourteenth century, is
characterized by champlevé on metal and usually mercury gilded. The historical debate on dating
these artworks has been carried out by many scholars, and was the inspiration to define a
noninvasive analytical methodology using XRF to objectively identify the origin of production,
5
Enamel Group, ICOM-CC, Experts’ Meeting on Enamel on Metal Conservation— The Frick Collection, New York, 2010
and to create a reliable quantitative database for future evaluations. The database now includes
the analysis of over a hundred Limoges artworks, including medallions and decorated caskets.
Among them, the Scrinium Cardinalis from Piedmont, a traveling chest from the so-called
treasure of Cardinal Guala Bicchieri (ca. 1150–1227), found in 1823 during the restoration of
Sant' Andrea basilica in Vercelli. This object is now at the Museo Civico di Arte Antica, Turin
along with other similar items probably belonging to the same collection. It is decorated with 15
medallions, 10 cantonali, and 24 brackets, producing a rich palette of colored enamels. For
comparable objects analyzed in this study see table 1. The Bicchieri collection originally
consisted of at least 5 scrini or cophini de opere lemovicensi—wooden boxes richly decorated
with Limoges enamels—as well as illuminated manuscripts and other precious objects. It now
largely remains in the Piedmont region and is partly dispersed in several museums including: the
Musée du Louvre and the Musée National du Moyen Âge in Paris, the Musée de Picardie in
Amiens, and The Metropolitan Museum of Art in New York (Castronovo 1992, 1995; Biron et
al. 1996). It was therefore evident that the main role of Cardinal Bicchieri’s original collection
was to define the technology used for the medieval enamel production in Limoges. Because
many collections may contain imitations that are not always easy to recognize, a result of the
nineteenth-century revival period in enamels (Marquet de Vasselot 1921; Wypyski 2002;
Cordera 2008), this study offers a solution for the identification of earlier and later enamel
production due to chemical differences in the glass (fig. 1). From a chemical point of view there are several indicators that can help to differentiate
the composition of enamels produced at different periods. Medieval enamels have a similar
composition to that of the Roman period—soda-lime glass opacified with tin or antimony oxides,
however, eighteenth- and nineteenth-century enamels are characterized by raw materials coming
from Germany, essentially lead-potash glass opacified with arsenic oxides. Coloring agents
determined by metal cations are almost the same except that in the Middle Ages impurities were
present in some minerals, while in more recent times they were added intentionally. An example
is the blue obtained with cobalt salts which is present in very low concentrations in medieval
works and usually related to nickel, bismuth, and arsenic impurities, while in modern works it is
present in greater quantities and usually lacks impurities. 6
Agostino, Aceto, and Castronovo
Authentication of Limoges Enamels by Noninvasive Techniques
Fig. 1. Comparison between two medallions, SS14, Church of San Sebastian, Biella, 6/21/2006
and OA9475, Musée du Louvre, Paris, 4/7/2008, characterized by the same iconographic
motif.
Another striking example is the presence, as coloring agents, of elements only known from the
nineteenth century: chromium (green, blue); uranium (yellow, brown, green); or vanadium
(green, blue, gray). These differences can be highlighted by chemical analysis as long as there is
a database, which contains enamels dated with certainty, to reference. EXPERIMENTAL
The analysis was carried out in situ, using an XRF spectrometer derived from a LITHOS 3000
portable unit (Assing Ltd.) equipped with a micro X-ray tube (Oxford TF3003) operating at 24
kV and 0.3 mA, with a molybdenum target providing polychromatic radiation with characteristic
emission peaks at 17.48, 17.37, and around 2.165 keV. The incident radiation was focused by a
tungsten collimator on an ellipsoidal surface of approximately 6 mm2. The emitted radiation was
collected with a Si PIN detector (Amptek), 5 mm2, energy resolution approximately 180 keV at
the Mn Kα line, and shaping time of about 6 µs. A laser interferometer gave precise location of
the analysis point with a working distance for all measurements of 9.4 mm. A live time
acquisition of 300s was used together with a geometry of 45° or 52°. Three different spectra
were acquired on the same analysis point to define an error on the measurement repeatability.
For each colored area acquisitions were carried out at different points. The analytical instrument
was placed on a tripod (fig. 2) for analysis in difficult conditions or when it was impossible to
7 Enamel Group, ICOM-CC, Experts’ Meeting on Enamel on Metal Conservation— The Frick Collection, New York, 2010
remove the object from the display case. Furthermore, to maximize the efficiency to detect
elements with low atomic number, all measurements were made using a helium flow (0.5 l/min)
to saturate the optical path between the sample and the detector. Table 1 presents the codes for
the analyzed enamels at the Louvre and for all previous analyzed enamels used for comparison. Fig. 2. Experimental setup used for analysis of the medallions of the Larcade Collection, Louvre.
Table 1. List of enameled objects analyzed and their designated codes.
Object
12 medallions
15 medallions
10 cantonali
24 brackets
15 medallions
1 ligature
5 plaques
18 medallions
15 medallions
6 enameled figures
Collection
Larcade Collection, Musée du Louvre, Paris
Traveling Chest, Collection of Guala Bicchieri, Museo Civico di Arte Antica, Turin
Codes
OA 9468 - OA9479
PMC1 - PMC9
PMCA - PMCT
“Free-Standing” objects, Museo Civico di Arte Antica, Turin
PM1S - PM32S
Medallions (mounted in wood choir), Church of San Sebastian, Biella
Small Chest, Collection of Guala Bicchieri, Museo Leone, Vercelli
Casket of Saint Catherine, Museo del Tesoro del Duomo, Vercelli
SS1 - SS23
ML1 - ML15
SC1 - SC6
8
All enamel colors were measured, but only blue and turquoise (almost always present) were
taken into account for comparison using multivariate analysis (Ebel 1999; Elam 2002; Rousseau
2004; Willis and Lachance 2004). For evaluating and quantifying the XRF data, the consolidated
model proposed by Van Espen (2000) with WinAxil software (Canberra) was used. This model
was tested using a set of certified reference materials (CRM) on the analysis of light matrices
obtained during recent years: National Institute of Standards and Technology (NIST), Colorado;
Corning Museum (Brill), New York; Brammer Standard Co., Texas; and Stazione Sperimentale
del Vetro, Venice. The calibration optimized the Van Espen algorithm for this matrix type in
order to adapt the quantitative approach to unknown samples. The enormous amount of data
collected required processing with multivariate statistical analysis, in particular principal
component analysis (PCA). Pearson algorithm was applied to all the elemental concentrations
previously determined with XRF, providing correlations between compositional differences for
oxides. RESULTS AND DISCUSSION As already stated, the study aimed to integrate a database previously developed using XRF
carried out on works from the Piedmont region and consisting of the percent composition for
each enamel. The results for the Larcade Collection are reported in table 2 and show a uniformity
consisting of at least three different groups (see fig. 4). Because XRF could not detect some
elements in the dark matrix, such as sodium, it prevented identification of soda-lime glass. There
was an indirect indication of a dark matrix when comparing the overall concentration of the sum
of sodium and magnesium with the absence of other fluxes. The K2O content, which is the only
other possible flux, remains below 2%, which supports the hypothesis that it is not the only flux
compound. Moreover, there is the presence of SnO2 as an opacifier, in agreement with the
literature on Limoges medieval production (Biron et al. 1996). The comparison with data from
nineteenth-century enamels in the reference database shows substantial differences from those of
the Larcade Collection. For instance, comparing two XRF spectra, one from the Larcade
Collection and one from San Sebastian (considered modern), it is observed that PbO content is
much higher than in the Louvre enamel (fig. 3). In the latter case it is assumed that lead replaces
calcium as a stabilizer, with high amounts of potassium as the flux; this composition represents a
typical example of lead-potash glass. 9 Enamel Group, ICOM-CC, Experts’ Meeting on Enamel on Metal Conservation— The Frick Collection, New York, 2010
Table 2. Compositional results for the enamels of the Larcade Collection expressed in weight
percent for each oxide. Errors are omitted, but are similar to those explained in Table 3. PbO
As2O3
SnO2
Fe2O3
K2O
CaO
CoO
CuO
ZnO
SiO2
OA 9468_dark blue
6.4%
0.1%
1.70%
1.10%
1.4%
5.3%
0.17%
0.05%
0.00%
55%
OA 9469_dark blue
6.6%
0.1%
1.80%
1.10%
1.2%
5.1%
0.17%
0.04%
0.01%
55%
OA 9469_light blue
9.7%
0.1%
2.31%
1.00%
1.2%
3.7%
0.14%
0.30%
0.00%
52%
OA9470_dark blue
7.3%
0.1%
1.94%
1.20%
1.3%
5.8%
0.20%
0.12%
0.01%
50%
OA9471_dark blue
8.5%
0.0%
1.73%
0.90%
1.4%
6.6%
0.17%
0.25%
0.46%
48%
OA9471_dark blue
6.8%
0.0%
1.45%
0.83%
1.4%
5.7%
0.12%
0.37%
0.37%
54%
OA9472_dark blue
8.0%
0.0%
2.00%
0.84%
1.2%
6.1%
0.14%
0.31%
0.44%
51%
OA9473_dark blue
7.5%
0.2%
1.90%
1.30%
1.4%
5.6%
0.20%
0.11%
0.00%
51%
OA9473_turquoise
9.5%
0.1%
2.25%
1.20%
1.1%
3.9%
0.15%
0.90%
0.00%
51%
OA9474_dark blue
8.0%
0.0%
1.97%
0.83%
1.2%
5.8%
0.15%
0.33%
0.46%
51%
OA9474_light blue
11.1%
0.1%
2.43%
1.30%
1.2%
4.6%
0.19%
0.25%
0.00%
49%
OA9475_light blue
9.9%
0.1%
2.29%
1.30%
1.4%
4.5%
0.16%
0.07%
0.00%
50%
OA9475_light green
8.9%
0.0%
2.33%
1.50%
0.9%
4.6%
0.08%
0.45%
0.00%
51%
OA9476_dark blue
8.3%
0.0%
1.76%
0.82%
1.3%
5.9%
0.15%
0.27%
0.46%
47%
OA9476_turquoise
10.3%
0.1%
2.29%
1.30%
1.2%
4.3%
0.17%
0.65%
0.00%
43%
OA9477_dark blue
8.9%
0.0%
1.83%
0.92%
1.3%
6.1%
0.14%
0.61%
0.47%
43%
OA9478_dark blue
7.9%
0.1%
1.83%
1.30%
1.6%
6.0%
0.21%
0.10%
0.01%
51%
OA9478_light blue
9.7%
0.1%
2.10%
1.30%
1.2%
4.0%
0.15%
0.27%
0.00%
50%
OA9479_dark blue
7.1%
0.2%
2.00%
1.20%
1.4%
5.8%
0.20%
0.07%
0.00%
53%
Furthermore, antimony and tin are replaced as opacifiers by the use of arsenic, which is also
typical of nineteenth-century production. Modern elements such as chromium, uncommon in
medieval works, were also present (Freestone and Bimson 2003). Comparison using a multicorrelation technique can better highlight the different periods of productions while linking them
to varied chemical compositions. In figure 4 all the different periods constituting the database are
grouped depending on the oxide content. Object codification (reported in table 1) allows the
possibility to identify dissonances between expected results for a given family, which also
depends on iconographical and historical studies. Homogeneity between the Larcade Collection medallions and those from the traveling
chest of Guala Bicchieri at the Museo Civico di Arte Antica, can be immediately determined
suggesting a unique origin from the same body of opus lemovicense or group B. 10
Fig. 3. XRF spectra comparison for energy versus intensity: A (top), Louvre and B (bottom), San
Sebastian church.
Fig. 4. Principal component analysis of the chemical composition for blue enamels analyzed by
XRF. 11 Enamel Group, ICOM-CC, Experts’ Meeting on Enamel on Metal Conservation— The Frick Collection, New York, 2010
Group C, which are the modern medallions from the church of San Sebastian, can be easily
identified too because of the higher arsenic, lead, and potassium contents. Interestingly one of
these medallions, sample SS22, is included in group A, enamels considered to be of medieval
origin. This suggests that it is the only enamel not stolen or replaced in the wooden choir stalls of
this church. Some works considered of uncertain attribution (e.g., the medallions and PM18S,
PM31S, PM16S, and the plaque) are classified within the medieval enamel group and on this
basis should be considered originals. To validate the proposed methodology table 3 illustrates the
comparison between already published data from scanning electron microscopy (SEM) and data
collected using XRF, both refer to the same blue enamel sampled in OA9472 medallion in the
Larcade Collection. Table 3. Comparison between results obtained by SEM (literature data) (*) and by XRF (+) on
sample OA9472, the only one of the set to have been previously measured. In the sample
analyzed by SEM measurement errors are not reported. SEM
OA9472*
PbO
As2O3
SnO2
Fe2O3
MnO
K2O
CaO
CoO
CuO
ZnO
SiO2
11.92%
1.67%
8.35%
1.34%
0.05
1.44%
5.16%
0.29%
0.61%
4.98%
43.3%
Na2O = 18.11%
MgO = 4.71%
Al2O3 = 1.93%
Total
= 105.66%
XRF
PbO
As2O3
SnO2
Fe2O3
MnO
K2O
CaO
CoO
CuO
ZnO
SiO2
OA9472+
8.0%
-
2.00%
0.84%
0.03%
1.2%
6.1%
0.14%
0.31%
0.44%
51%
error
±0.6%
-
±0.03%
±0.09%
±30 ppm
±0.09%
±0.1 %
±0.004%
±2 ppm
±2 ppm
±2 %
Na2O = ND
MgO = ND
Al2O3 = 1.7%
Total
= 74.76%
It was observed that results between SEM and XRF are consistent despite some disparity due to
micro versus macro analysis, respectively. Agreement was found for PbO and SiO2 content and
on the dark matrix (for XRF) with sodium and magnesium content (for SEM). More relevant
differences were observed in concentrations for tin and the transition elements. Data obtained
from the analysis of blue enamel are the most significant, because of the abundance of this color
in Limoges works. Further support is given when compared to the spectra of turquoise enamel
from various objects, whose results are similar to the blue enamel (fig. 5). 12
Fig. 5. Comparison of XRF spectra of turquoise enamels collected in different collections. Table 4. Summary of differences between Larcade Collection and modern enamels. Network Formers
Larcade Collection
19th c. Copy
high % of SiO2
PbO below 15%
low % of SiO2
PbO between 20–40%
Stabilizers
SiO2 47–56%
PbO 7–11%
SiO2 37–48%
PbO 16 – 25%
Opacifiers
CaO below 10%
CaO 3.4–5.8%
CaO under 5% + PbO
CaO 1.8–2.7%
Flux
Larcade Collection
Sn or Sb
Sn 1.30–2.40%
As < 0.2%
Na
19th c. Copy
As
As 0.5–3.5%
high % of K
K2O 2.1–5.5%
All results are summarized as follows and illustrated in table 4: in medieval enamels the
flux is mainly based on sodium and for modern enamels mainly on potash; the stabilizer is a
calcium compound in medieval enamels and a lead compound in modern enamels; the opacifier
is a tin or antimony compound in medieval enamels and arsenic in modern enamels. CONCLUSIONS
The XRF analysis of light matrices, such as enamels, allows for quantitative results to be
13 Enamel Group, ICOM-CC, Experts’ Meeting on Enamel on Metal Conservation— The Frick Collection, New York, 2010
obtained and is comparable to other analytical techniques. Furthermore, the noninvasiveness of
this portable instrumentation allows a large amount of information to be collected in situ, without
any sample preparation. This work expanded the database concerning Limoges medieval
production, and showed that the Larcade Collection medallions in the Louvre were of medieval
manufacture. The portable XRF approach is therefore proposed as an analytical method to be
used in the preliminary study of medieval enameled artifacts.
REFERENCES
Biron, I., P. Dandridge, and M. Wypyski. 1996. Techniques and materials in Limoges enamels.
In Enamels of Limoges 1100–1350, eds. B. Boehm and E. Taburet-Delahaye. New York, The
Metropolitan Museum of Art. 48–62 and 446–448.
Castronovo, S. 1992. Il tesoro di Guala Bicchieri cardinale di Vercelli. In Gotico in Piemonte,
ed. G. Romano. Torino, Editris. 166–239.
Castronovo S. 1995. Limoges et l’Italie: le cas du Piémont au XIIIe siècle. In L’œuvre de
Limoges: Art et histoire au temps des Plantagenêts, actes du colloque. Musée du Louvre, Paris.
341–389.
Cordera, P. 2008. Sugli smalti di Limoges. Note sulla fortuna ottocentesca di un’arte “minore”.
http://www.oreficeriadriatica.it
Ebel, H. 1999. X-ray tube spectra. X Ray Spectroscopy 28:255–266.
Elam, W.T. 2002. A new atomic database for X ray spectroscopy calculations. Radiation Physics
and Chemistry 63:121–128.
Freestone, I. C. and M. Bimson. 2003. Possible early use of chromium as a glass colourant.
Journal of Glass Studies 45:183–185.
Longoni, A. and C. Fiorini. 2006. X-ray detectors and signal processing. In Handbook of
Practical X-Rays fluorescence analysis, eds. B. Beckhoff, B. Kanngießer, N. Langhoff, R.
Wedell, and H. Wolff. Germany, Springer Berlin Heidelberg. 203–259.
Marquet de Vasselot, J. J. 1921. Les émaux Limousins de la fin du XVème siécle et de la
première partie du XVI siécle, Etude sur Nardon Penicaud et ses contemporains. Paris
Rousseau, R. M. 2004. Some consideration on how to solve the Sherman equation in practice.
Spectrochimica Acta B 59:1491–1502
14
Van Espen, P. 2000. ED-XRF spectrum evaluation and quantitative analysis using multivariate
and nonlinear techniques. JCPDS-International Centre for Diffraction Data, Advances in X-ray
Analysis 43:560–569.
Willis, J. P. and G. R. Lachance. 2004. Comparison between some common influence coefficient
algorithms. X Ray Spectroscopy 33:181–188.
Wypyski, M. 2002. Renaissance enameled jewelry and 19th century Renaissance revival:
Characterization of enamel compositions. In Materials Issues in Art and Archaeology VI, eds. P.
B. Vandiver, M. Goodway, and J. L. Mass. Pittsburgh, Materials Research Society. 223–233.
ACKNOWLEDGMENTS The authors would like to thank the following individuals for allowing us to carry out analytical
work on their collections: Dr. Pagella, Director, Museo Civico di Arte Antica – Palazzo
Madama,Turin; Dr. Rosso, Director, Museo Leone, Vercelli; Dr. Cerutti Garlanda, Scientific
Director, Museo del Tesoro del Duomo,Vercelli; Dr. Antoine, Curator, Musée du Louvre, Paris
and Biella Commune. Special thanks also to Dr. Biron, Senior Research Scientist and Engineer,
Laboratoire du Centre de Recherche et de Restoration des Musées, Paris for the availability and
exchange of information and Dr. Fenoglio for helpful discussion.
AUTHORS
ANGELO AGOSTINO, Senior Scientist, corresponding author
Dipartimento di Chimica Generale e Chimica Organica, Università di Torino, corso M.
d’Azeglio, 48, 10125, Torino; Centro di Eccellenza NIS (Nanostructured Interfaces and
Surfaces), Università di Torino, tel. 011 6707585, fax 011 6707591, [email protected]
Mr. Agostino has a Ph.D. in Chemistry and is Senior Scientist at the University of Turin, Italy, in
the Department of General Chemistry. He has worked in international large-scale research
facilities such as the European Synchrotron Radiation Facility, Grenoble, and spent over ten
years as a scientist in an academic environment. He is an expert in X-ray Fluorescence and X-ray
Powder Diffraction and has developed sophisticated research techniques involving materials
analysis and surface technology. He has spent time at the Getty Conservation Institute as visiting
scientist involved in research on XRF applications. He has spent the last five years researching
noninvasive techniques for authentication of artworks.
MAURIZIO ACETO, Senior Scientist
Dipartimento di Scienze dell'Ambiente e della Vita, Università del Piemonte Orientale, via
Teresa Michel, 11, 15100, Alessandria; Centro Interdisciplinare per lo Studio e la Conservazione
dei Beni Culturali (CenISCo), Università del Piemonte Orientale, via Manzoni, 8, 13100,
Vercelli
SIMONETTA CASTRONOVO, Curator
Museo Civico di Arte Antica – Palazzo Madama, p.zza Castello, 10123, Torino
15 16
ON-SITE ANALYSIS OF ENAMELS ON METAL FROM THE FIFTEENTH TO THE
NINETEENTH CENTURY: AN ATTEMPT TOWARDS DIFFERENTIATION
BETWEEN GENUINE ARTIFACTS AND COPIES
BURCU KıRMıZı
AND PHILIPPE COLOMBAN
ABSTRACT – A selection of 22 Chinese cloisonné and 13 Limoges painted enamels from the
fifteenth to the nineteenth century was studied on-site in the storage rooms of the Musée des Arts
Décoratifs in Paris using a portable Raman spectrometer (Kırımızı et al. 2009, 2010). The aim of
this study was to identify the composition of amorphous (glass matrix) and crystalline (pigments,
signatures of processing) phases by means of Raman spectrometry which might also serve as a
tool for discriminating between different production periods as demonstrated for a variety of
enameled glass and ceramic artifacts in previous studies (Colomban and Tournié 2007;
Colomban 2008; Ricciardi et al. 2009).
INTRODUCTION AND TECHNIQUE
The earliest examples of enameling on metal appear to be the rings from the Mycenaean tombs
dating to the second millennium BC in Cyprus (Gauthier 1985). Different types of enameling
techniques such as champlevé and cloisonné were being used in Celtic productions dating to as
early as the third century BC. During the eleventh century, the Byzantines developed the art of
cloisonné enameling to a very high level and this technique had reached China by the fourteenth
century (Dalton 1961). By the Ming period (1368–1644), the cloisonné technique had been well
established with the use of a palette of six to eight colors and further enlarged by mixing colors
and the addition of opacifiers (Biron and Quette 1997). At the time of the development of
cloisonné enameled objects in China, this technique had disappeared in Europe with the
emergence of a new technique called “painted enameling” towards the end of the fifteenth
century in Limoges, France. Using this technique, Limoges artisans created sophisticated
17
paintings as multi-layered enamels on copper supports. During the seventeenth century the
quality of the enamels had started to decrease until a remarkable revival in the nineteenth
century. The workshops produced modern Limoges School pieces and also replicas of
Renaissance enamels, which were often being sold as originals (Rohrs and Stege 2004).
Raman spectrometry has been used extensively in the last decades for a wide range of
archaeological and historical artifacts and remains. One of the most significant reasons for the
increasing value of Raman spectrometry is that it is a non-destructive technique and does not
require sample preparation. In the case of archaeological and historical objects, where moving
them from the museum is not always possible due to their size and preciousness, the portable
Raman spectrometers make it possible to analyze them in situ.
Vitreous materials, such as glazes and enamels, are all silicate-based and have a network
of SiO4 tetrahedra. The SiO4 tetrahedron is a covalent entity and has a well-defined vibrational
signature which gives a characteristic Raman spectrum. The connectivity of the SiO4 tetrahedra
is based on the bridging oxygen atoms located at the corners of the molecule. These SiO4
tetrahedral connections are modified by the incorporation of alkali, or alkaline earth metal ions,
or both, in the glass structure, resulting in changes in the properties of the glass, such as melting
temperature, viscosity, color, etc. The presence of these modifiers in the glass structure leads to
the formation of different types of tetrahedral connections which are expressed by the Qn
notation where “n” is the number of bridging oxygen atoms varying between 0 to 4.
Consequently, the depolymerization of the SiO4 network by these modifying species is reflected
in the intensity, line width, and spectral position of the Raman bands.
The characteristic Raman spectrum of glass consists of two broad peaks as bending and
stretching modes at around 500 and 1000 cm-1, respectively. Five spectral components as Q0, Q1,
Q2, Q3, and Q4 are postulated for the Si-O stretching region according to the Qn notation.
Different parameters that are extracted from the Raman signature of the enamels such as the
wavenumber maxima of the Si-O stretching and bending components and their intensity ratio (Ip,
the polymerization index = A500/A1000) are used for the identification of different glass
compositions. The polymerization index values directly correlate to the glass composition and
firing temperature (Colomban 2003).
18
Kırmızı and Colomban
On-site Analysis of Enamels on Metal from the Fifteenth to the Nineteenth Century
EXPERIMENTAL
The measurements were performed on-site in the storage rooms of the Musée des Arts Décoratifs
in Paris using a Raman spectrometer (HE532 Horiba Jobin-Yvon) with an Nd:YAG laser light
source providing a 100 mW, 532 nm line (visible green), in conjunction with a Nikon 50x ultra
long working distance objective (fig.1) (Kırımızı et al. 2009, 2010). The raw spectra collected
were then subjected to the process of baseline subtraction by using LabSpec (Dilor) software in
order to see the Raman signature of the molecule Si-O better and eliminate the contribution of
the Boson peak (Colomban 2008). The deconvolution of the different spectral components, as Qn
for stretching and Qn’ for bending regions, is done by Origin software as described in Ricciardi et
al. (2009).
Fig. 1. Experimental set-up for the Raman spectrometer in the Musée des Arts Décoratifs storage
room.
RESULTS AND DISCUSSION
The characterization of Chinese cloisonné and Limoges painted enamels as a function of their
composition and color was carried out by means of Raman spectrometry for the first time in this
study. Additionally, an attempt was made for the differentiation between genuine artifacts and
nineteenth-century restorations or fakes for Limoges examples. According to the described
19
methodology, different compositions were identified (table 1 and fig. 2) (Kırımızı et al. 2009,
2010).
Table 1. Glass compositions for enamels analyzed.
Chinese cloisonné
th
th
th
Limoges painted enamels
th
Lead-potash-lime [A]
15 –16 and 18 –19 century
16th and 19th century
Soda-rich [B]
16th–17th century
15th–16th and 19th century
Soda-lime [B’]
17th century
15th–16th century
Fig. 2. Plot of the Si-O stretching maximum values versus bending maximum values for Chinese
cloisonné and Limoges painted enamels.
Most of the Chinese cloisonné enamels fall into the lead-potash-lime group while the soda-lime
group is the most common for Limoges enamels as also revealed by previous studies (Perez y
Jorba et al. 1991; Biron and Quette 1997). One of the sixteenth-century Chinese cloisonné
20
Kırmızı and Colomban
On-site Analysis of Enamels on Metal from the Fifteenth to the Nineteenth Century
objects was found to be in the soda-rich group, suggesting the production of a different workshop
or its assignment to a later date. The polymerization index (Ip) for the soda-lime group varies
between 2–3 according to the calcium content and a medium firing temperature, whereas the Ip
values for the lead-potash-lime group are lower, between 1–2 due to the lead content. In some
cases, the identification of crystalline and amorphous phases by non-destructive Raman analysis
can be used as post quem date markers, such as the confirmation of lead arsenate as an opacifier
in nineteenth-century Limoges works. On the other hand, fluorite was only found in Chinese
cloisonné productions. Cassiterite was also identified as an opacifier in Limoges samples dating
from the sixteenth to the nineteenth century. Hematite red and Naples yellow pigment variations
were also detected which give characteristic Raman signatures in both types of enamels. Among
the different pigments detected by this method, cobalt silicate was used for blue and green
enamels and chromate-based compounds for pink enamels. The very strong light absorption of
some red enamels seems consistent with the use of copper nanoparticles dispersed in the glassy
phase. If one of these markers is not sufficient to reach an assignment for dating, the combination
of many of them is generally a proof of embellishments, undocumented restoration procedures,
or fakes. A good knowledge of Raman spectroscopy and of the ancient and modern technologies
is mandatory to have reliable conclusions. It should be noted that for old artifacts of the same
origin or that have been in the same place for long periods, the intensity of the Raman signal
recorded with standard conditions is an additional piece of information to compare the age of
different glasses.
ACKNOWLEDGMENTS
The authors would like to thank Béatrice Quette and Monique Blanc from the Musée des Arts
Décoratifs, Paris for their invaluable cooperation in the study.
REFERENCES
Biron, I. and B. Quette. 1997. Les premiers emaux Chinois. Techne 6.
Colomban, Ph. 2003. Polymerization degree and Raman identification of ancient glasses used for
jewelry, ceramic, enamels and mosaics. Journal of Non-Crystaline Solids 323(1–3):180–187.
Colomban, Ph. and A. Tournié. 2007. On-site Raman identification and dating of ancient/modern
stained glasses at the Sainte-Chapelle, Paris. Journal of Cultural Heritage 8(3):242–256.
21
Colomban, Ph. 2008. On-site Raman identification and dating of ancient glasses: Procedures and
tools. Journal of Cultural Heritage 9(1):e55–e60. http://dx.doi.org/10.1016/jculher.2008.06.005
Dalton, O. M. 1961. Byzantine Art and Archaeology. Dover Publications: New York.
Gauthier, M. M. 1985. Emaux. Encyclopédie Universalis. Universalis: Paris 6.
Kırmızı, B., Ph. Colomban, and B. Quette. 2009. On-site analysis of Chinese cloisonné enamels
from fifteenth to nineteenth centuries. Journal of Raman Spectroscopy 41(7):780–790.
http://dx.doi.org/10.1002/jrs.2516
Kırmızı, B., Ph. Colomban, and M. Blanc. 2010. On-site analysis of Limoges enamels from
sixteenth to nineteenth centuries: An attempt to differentiate between genuine artefacts and
copies. Journal of Raman Spectroscopy. http://dx.doi.org/10.1002/jrs.2566
Perez y Jorba, M. Rommeluere, and C. Bahezre. 1991. Microstructure d’une plaque d’émail
peint de Limoges du XVIé siècle. Studies in Conservation 36(1):76–84.
Ricciardi, P., Ph. Colomban, A. Tournié, and V. Milande. 2009. Nondestructive on-site
identification of ancient glasses: Genuine artefacts, embellished pieces or forgeries? Journal of
Raman Spectroscopy 40(6):604–617. http://dx.doi.org/10.1002/jrs.2165
Röhrs S. and H. Stege. 2004. Analysis of Limoges painted enamels from the 16th to 19th centuries
by using a portable micro X-Ray fluorescence spectrometer. X-Ray Spectrometry 33.
AUTHORS
BURCU KıRMıZı , Scientist, corresponding author
Middle East Technical University Graduate School of Natural and Applied Sciences
Archaeometry Program, 06531, Ankara, Turkey, [email protected]
Ms. Kırmızı holds an M.S. degree in Archaeometry from the Middle East Technical University
(METU) in Ankara, Turkey, where she was a research assistant from 2006 to 2008. In 2008 to
2009, she worked in the Laboratoire de Dynamique, Interactions et Réactivité (LADIR) at the
Université Pierre-et-Marie Curie in Paris as a fellow of the Scientific and Technological
Research Council of Turkey (TÜBİTAK). At LADIR, she studied the application of Raman
spectrometry for the characterization of vitreous materials. Currently, she is a Ph.D. candidate in
Archaeometry at METU and she is working on the characterization of Byzantine and Early
Ottoman ceramics from the western Anatolia region of Turkey.
PHILIPPE COLOMBAN, Scientist
Laboratoire de Dynamique Interactions et Réactivité (LADIR), UMR 7075, CNRS, UPMC, 2 rue
Henri Dunant, 94320, Thiais, France
22
23
REVIEWING THE CONSERVATION OF UNSTABLE ENAMELS AT THE VICTORIA
AND ALBERT MUSEUM
JUANITA NAVARRO
ABSTRACT – During the preparatory work for the new Medieval and Renaissance Galleries at
the Victoria and Albert Museum, London, the condition of many unstable enamels was assessed,
including basse-taille enamels on silver and Limoges painted enamels on copper. A major
concern for the conservators was the damage being caused by previous coatings to the enamels.
Conservators treated the enamels for display while searching for ways to solve the underlying
problems of the removal of soluble salts and unwanted coatings from crumbling enamel surfaces.
INTRODUCTION
The new Medieval and Renaissance Galleries at the Victoria and Albert Museum (V&A),
London, opened at the end of 2009. The project provided an opportunity to conserve several
basse-taille enamels on silver and Limoges painted enamels on copper which were chemically
unstable, as well as assess their condition and past treatment. For some, this was their second or
even third conservation treatment in recent times. When proposing conservation treatments, the
principle of minimal intervention was uppermost, not only because of the condition of the
enamels and the ethical guidelines, but also due to time constraints.
In its earliest stages chemical instability will appear on the enamel surface as an almost
imperceptible bloom or as a smeary coating resulting from soluble salts migrating to the surface.
Fluctuations in temperature and relative humidity cause more soluble components to migrate and
collect on or near the surface, a process that creates tiny fissures in the glass also referred to as
crizzling. The salts either deliquesce by absorbing moisture from the environment or crystallize
in drier conditions. Both liquid and crystals exert pressure in the micro-cracks leading to further
fracturing of the glass. As the crizzling progresses fine enamel flakes detach from the surface.
24
The most unstable enamel colors are dark blue and mulberry and these are the most problematic
areas to treat. The deliquesced salts cause the cracks to disappear visually and the translucent
enamels to appear more brilliant, however, removing the soluble salts from the surface of an
unstable enamel is recommended as the salts are hygroscopic, increase the alkalinity at the
surface, and so lead to further degradation (Fearn 2002).
COATINGS APPLIED TO ENAMELS
Between the 1960s and 1980s coatings were sometimes applied to unstable Limoges painted
enamels, either to the whole surface or to the degraded areas only. The aim of the coatings was to
consolidate the enamel surfaces and to provide a barrier layer against environmental fluctuations,
thereby stopping or slowing down ongoing degradation of the enamel and the metal substrate.
Objects with champlevé and basse-taille enamels have large areas of exposed metal, which was
often coated to prevent corrosion. Unfortunately, the coating was sometimes applied to the
enamel surface as well. The specific coatings used are not always known. Early Metals
Conservation records at the V&A from the 1970s, show that acrylic resins, such as Incralac
(which contains benzotriazole, and used on silver and silver-gilt) and cellulose nitrate lacquers,
such as Ercalene and Frigilene, have been used in the past. Test coatings, such as wax (1987), are
known to have been applied to unstable enamels but documentation is incomplete. One coating
was analyzed (1972) at the National Gallery, London, and found to be polyvinyl acetate.
Conservation documentation for one plaque (1999) stated that the coating on a Limoges painted
enamel appeared to be water-soluble. These coatings, however, failed to provide the protection
that was originally intended because they create microclimates which promote degradation
processes underneath. Currently more attention is being given to improving the display and
storage conditions of the enamels. Today the only lacquer in regular use at the V&A is Frigilene,
used on silver and silver-gilt and never allowed to coat any of the enameled areas. Meanwhile
conservators have to deal with the results of past conservation treatments, where severely
disrupted surfaces provide the most challenging problems.
CURRENT CONDITION AND TREATMENT
The condition of the enamels treated and of the coatings present varied considerably and the
conservation treatment method was selected accordingly. Treatments were carried out using
25
Navarro
Reviewing the Conservation of Unstable Enamels at the Victoria and Albert Museum
binocular magnifiers or a microscope. When a brush was used to apply solvents, particularly
mixtures containing water, absorbent paper was used to remove as much moisture as possible
before touching the surface of the enamel. One Limoges painted enamel had a thick glossy
coating over the front and back, giving the surface an unpleasant and misleading appearance (fig.
1). Salts on the blue and mulberry enamels were growing through the coating, which appeared to
have changed little since its application and was thoroughly adhered to the enamel. It was
possible to sweep the crystallized salts with a sable brush to a sound area where they could be
removed with a micro-vacuum, however the coating was retained.
Fig. 1. Plaque, St. Christopher Crossing a River with Christ on One Shoulder, attrib.
‘Monvaerni’ Master, ca. 1484–97, Limoges, 18.4 x 21.2 cm, C.143-1911. Detail
showing uncharacteristically glossy and unsightly appearance produced by the coating.
Photo courtesy of J. Navarro.
Several enamels had more problematic coatings, such as 22 small insets of basse-taille on silver
on an altar cross (ca. 1470–1490, Florence, 49 x 33.5 cm, M.580-1910) (see Jordan 2009–10).
Again, the blue and mulberry enamels were unstable. The plaques had a very unsightly
appearance as the coatings (polyurethane) had lifted in many areas; there were large amounts of
salts that had deliquesced under the coating. The coating could be removed, but not without
removing some tiny flakes from the surface. Loose corrosion products were removed by
aspiration with a miniature vacuum tweezer unit (Jordan 2009–10) or with a dampened sable
26
brush when liquid. Minimal local consolidation was necessary to severely disrupted areas using a
weak solution of acrylic resin.
The Master of the Louis XII Triptych (ca. 1498–1512, Limoges, 44 x 45 cm, 552–1877)
comprises nine painted enamel plaques, all of which were unstable, but the main three panels
showed the most disrupted blue enamel observed so far. Crystallized salts were growing through
the sugary mixture, which also contained the remains of a previous coating or consolidant. In a
few spots, the salt growth extended from the blue to the neighboring stable white enamel causing
damage to those areas. It was no longer possible in some areas to remove dry salts by aspiration
with a micro-vacuum as this would remove unacceptable amounts of loose original material. The
acrylic consolidant applied in 1999 was reactivated with minimal amounts of organic solvent.
Small spots had further applications of dilute acrylic resin as a consolidant only where absolutely
necessary to support loose flakes. Although the appearance has improved slightly the underlying
problem has not been tackled and the soluble salts remain in place.
CONCLUSION
There will never be easy solutions for the complex problems encountered in the treatment of
unstable enamels. It will always be necessary to make decisions on an individual basis for each
object. Fortunately, conservation has developed a culture of sharing information that has enabled
improvement in current techniques, and there is far more practical and scientific information
available than ever before to assist in treatment decisions.
REFERENCES
Fearn, S. 2002. Continued studies in the deterioration of glass. V&A Conservation Journal
42(Autumn):12–13.
Jordan, F. 2009–10. Deteriorated enamelled objects: Past and present treatments. V&A
Conservation Journal 58(Autumn):39–40.
AUTHOR
JUANITA NAVARRO, Senior Conservator
Ceramics and Glass Conservation, Victoria and Albert Museum, Cromwell Road, London SW7
2RL, UK, Tel. +44 (0) 20 7942 2088, [email protected]
Ms. Navarro specializes in the study and treatment of ceramics and glass, and earned a BA in
27
Navarro
Reviewing the Conservation of Unstable Enamels at the Victoria and Albert Museum
Fine Art before training in Conservation of Ceramics and Related Materials at West Dean
College, Great Britain. After several years as a freelance conservator she returned to West Dean
for three years as a part-time Assistant Tutor. In 1992 she joined the staff of the Victoria and
Albert Museum. Her research focuses on the seventeenth-century enameling technique of émail
en résille sur verre. She has published several articles related to the preservation and treatment of
ceramics and glass in multiple journals, and has been an Accredited Conservator-Restorer since
1999 and a Fellow of the International Institute for Conservation since 2002.
28
29
REVERSIBILITY AND COMPATIBILITY OF RESTORATION MATERIALS FOR
PAINTED ENAMELS
BÉATRICE BEILLARD
ABSTRACT – Past restorations encountered during the treatment of painted enamels often
appear as multi-layered products, which eventually react with the environment as well as the
materials that make up the object—in this case glass and copper. These restorations gradually
deteriorate and are further compromised by the degradation products produced by unstable glass.
This paper will discuss the multiple treatments observed on painted enamels and the issues of
reversibility.
INTRODUCTION
In France, conservation reports on enamels cannot be located before 1950. The first time this
kind of documentation is mentioned is in the Venice Charter, Article 16, in 1964 (ICOMOS),
however, it was not common practice to provide written documentation until the advent of
training centers in Europe, particularly the Instituto Centrale di Restauro in Rome created in
1939. The first conservation reports documenting the treatment of French artworks belonging to
museums were by Albert France-Lanord (1915–1993) at the Laboratoire d’Archéologie des
Métaux (LAM) in Nancy, and he treated most of the deteriorated enamels in public collections.
Before him, there are just invoices from restorers, such as Alfred Corplet, the Maison André, or
Oudard in Reims.
The old restorations on enamels are typically composed of several layers of diverse
coatings to protect the copper; various materials to fill the losses in the enamel; and pigments and
mediums for inpainting. The ageing of these different materials leads to new treatments by
conservators. This intervention consists of either partial reduction of the deteriorated restoration
materials or a complete “de-restoration” when the old materials no longer fulfill their function—
30
to aesthetically improve and reintegrate the appearance of the enamel.
The analysis of past restoration materials can be cross-checked with historical accounts
(see Gall Ortlik 2001), however, it is difficult to link the published “recipes” with the
interventions that have been analyzed. Several examples of recent de-restorations allow us to
evaluate the materials used in the nineteenth century and complete the story of these enamels.
Subsequent restorations often take place when either the status of the object or its ownership
changes. A prime example are the nine large oval enameled plaques depicting Roman gods and
virtues by Pierre Courteys (ca. 1520–1586), Musée National de la Renaissance in Ecouen: three
sales and three corresponding restorations in 1800, 1844, and 1856 (the date of the acquisition by
the French state) (see Brandenbourg and Beillard 2003).
PREVIOUS TREATMENTS
“Hot Restorations”
Hot restorations are difficult to identify if the enamel has been re-gilt by firing in the kiln.
Sometimes part of the damaged object is remade in enamel and this new piece is attached on top
of the original copper support. Although, the new insert matches the original material, cold
restoration is necessary around the perimeter to disguise the join. The presence of “patches”
show the difficulty of re-firing an enamel over 600°C, with the risk of losing the gilt decoration
and de-vitrification of the enamels.
Examples
Tazza with cover, the Triumph of Neptune and Amphitrite, 16th c., Museum of the Petit
Palais, Paris, inv. PP.02419: Two patches were located in the middle and on the side of
the lid. The patches complete the composition but were done in a different style.
Plate, The Laocoön, ca. 1560, Pierre Courteys, Museum of the Fine Arts (School of Fine
Arts), Limoges, inv. 88453: Badly damaged, the plate has been restored with 14
enameled patches attached with tin-lead solder to the damaged copper. The radiographs
revealed a big hole at the level of the right knee of the father. Here the restoration
completes the composition.
Restorations with Tin-lead Solder
Restorations with tin-lead solder have been used since the eighteenth century. Without strong
adhesives, this fast and reliable solution can be applied for consolidation and reattachment of
31
Beillard
fragments. For good adhesion the restorer needs a fairly wide band of copper. It is obtained by
scratching the enameled surface around the area to be repaired, to expose the copper substrate.
Then the solder is melted and flowed over the surface of the copper to be joined and abraded
after rapid hardening. These strong restorations are very difficult to remove and are considered
irreversible.
Examples
Plaque, The Prophet Malachiel, ca. 1543, Léonard Limosin, Musée national de la
Renaissance, Ecouen, inv. Ec 306: the head of the prophet is new, and on the other side
the counter enamel is transparent, contrasting with the red one of Limosin.
Holy-water pot, St. Paul, Jacques II Laudin, 17th c., Musée des Beaux Arts, Dijon, inv.
Cat 1325: The numerous tears in the copper are fixed with solder as well as the bottom of
the bowl.
“Cold Restorations” and Coatings
Certainly beautiful at the time of their creation, these restorations do not age well. Loss of
cohesion between the different layers, weak adhesion to the copper, flaking of the varnish, and
changes in the inpainted colors are the most common problems that occur over time. The
aesthetic problems, such as darkening and yellowing of the inpainted areas, attracts the most
negative attention, but more serious are the corrosion products resulting from some restoration
materials becoming more acidic over time and affecting the copper support. Removal of this
material must be considered a measure of prevention. The main characteristic that these
restorations have in common is the layering of at least four materials with different solubilities.
Example
Plaque, Aeneas and Anchises, Pierre Courteys, mid 16th c., Musée des Beaux Arts,
Limoges, inv. 43: It represents a classical example of this kind of restoration—a resinous
varnish is applied over a layer of oil paint, which is over a putty made of calcium
carbonate with a proteinaceous binder, over a layer of wax directly applied on the copper.
Copper corrosion products can occur when materials are used for treatment which increase in
acidity over time. Beeswax was systematically used during the nineteenth century as a protective
layer on the copper or on deteriorated enamel, i.e. crizzled or weathered glass. The acidic nature
of the beeswax results in the development of copper carbonates migrating to the surface through
32
cracks and into the wax coating or moving under the enamel causing detachment. Often applied
with heat, the wax diffuses into the enamel and is difficult to remove.
Examples:
9 Oval Plaques, Pierre Courteys, 1559, Musée National de la Renaissance, Ecouen, inv.
ECl 1497 to ECl 1504: The most corrosive materials on these enamels are the wax, the
plaster fills, and the putties with oil binders.
Tazza, Pyrame and Thisbé, Pierre Reymond, 1537, Museum of the Fine Arts, Limoges,
inv. 2007.7.1: The corrosion of the copper results from the acidification of the linseed oil.
Layers in contact with the copper contain a mixture of plaster, linseed oil, and kaolin. On
the surface, a recent restoration consists of a glycerophtalic (alkyd) resin with Prussian
blue pigment. Ageing of the material causes a darkening and a deformation of the
surface.
The natural resins were applied with heat and present immense shrinkage upon drying, creating
strong tension at the interface of the resin and glass surface. Shellac or Canada balsam was used
as protective layers, glues, or gap-fillers. They do not corrode the metal, but they become brittle
with time and flake easily. Used to fill the losses, they crumble and degrade the inpainting as
well. The proteinaceous binders are very sensitive to humidity and act as sponges, absorbing
moisture at the surface of the enamel, when they aren’t covered by another material.
The resins used as varnish (i.e. gum mastic, dammar, sandarac) oxidize easily (oxidative
hydrolysis) and no longer adhere to the glass. Strong yellowing and flaking are difficult to
regenerate, but they can be reduced with isopropanol or alcohol without removing the entire
restoration.
Examples
Plate, The Month of Mars, Master IC, late 16th c., Musée du Louvre, Paris, inv. R 316:
Gap-filling using shellac covered by a varnish with gum mastic which has yellowed and
scaled.
Plaque, Story of Psyche, Leonard Limousin, ca. 1540, National Museum of the
Renaissance, Ecouen, inv. Ec 1907: The restoration includes five different layers which
lost their adhesion. The first contains calcite with animal skin glue. Others consist of
sandarac and white pigments (lead carbonate and zinc oxide). The copper is not corroded
but the restoration has degraded and crumbled.
33
Beillard
Synthetic resins, however, are much easier to remove mechanically or by softening them in a
solvent. Harder resins, unfortunately, are less reversible and were used during the second half of
the twentieth century due to advancements in polymer or macromolecular chemistry, i.e. the
tridimensional resins. A favorite one for restorers is polyester resin used to fill losses. Their bad
adhesion, instability to light, and severe shrinkage make them poor materials, but are reversible
when applied in thin layers.
During an important sale of enamels in 2009, all the objects presented were covered with
a polyurethane varnish (PUR). Was it the preference of a dealer or a collector’s taste for an
excessive gloss? This product, applied fifteen years ago, continues to polymerize by contracting,
producing bubbles, and lifting up from the surface. Under magnification, traces of gold were
visible, which were attached to the underside of the lifting varnish. This varnish may have peeled
the gold off the surface because of the shrinkage that can occur after the resin cross-links.
Examples
Triptych, ca. 1520, private collection: PUR varnish was applied to one side of the triptych
which had deteriorated glass. Formation of salts, a result of the dehydration of the
enamel, is pushing the varnish up from the glass surface. Should it be removed and how?
Dish, 16th c., private collection: PUR varnish was applied to the surface of the enamel
with gold. Removing the varnish is achieved only with long exposure to acetone or
aromatic solvents (as a vapor or with a compress). How will the object react to a
treatment that dries out the glass? And what will be left of the gold on the surface?
CONCLUSION
Past and current treatments involve the application of many different layers and inevitably
degrade overtime and can interact with the copper. The ideal restoration would be made of just
one material that is stable and reversible. Is there one material that can serve as a fill material,
consolidant, coating, and medium for inpainting? This is the direction to work towards. These
enamels have survived for four centuries, and in many cases several restoration campaigns,
before arriving into the current hands that care for them. Reversibility must remain our first
concern to allow future treatment to continue if necessary.
34
REFERENCES
ICOMOS. 1964. The Venice Charter. International Charter for the Conservation and Restoration
of Monuments and Sites. Second International Congress of Architects and Technicians of
Historic Monuments, Venice. http://www.international.icomos.org/charters/venice_e.htm
Gall Ortlik, A. 2001. A Concise Bibliography on the Technology, Deterioration, and
Conservation of Enamels on Metal. http://www.icom-cc.org/54/document/emcn-a-concisebibliography-by-agnes-gall-ortlik-2001/?id=91
Brandenburg, A. and B. Beillard. 2003. Les grands émaux de Pierre Courteys. Techne 17:53–60.
Analysis carried out by Dominique Fromageot, CNEP, Ensemble Universitaire des Cézeaux,
Aubière Cedex.
Reports by A. France-Lanord, Musée du Louvre and Musée de Cluny, Conservation Department.
AUTHOR
BÉATRICE BEILLARD, Conservator in Private Practice
Restaurateur des Musées de France, [email protected]
Ms. Beillard graduated from the Institut Français de Restauration in 1982, in the field of
ceramics, and specializes in the restoration of enamels. For twenty-five years she has maintained
the collections for the Musée du Louvre, Département des Objets d’Art; Musée de la
Renaissance à Ecouen; and the Musée du Moyen Age Thermes de Cluny, as well as the
collections of the Musée de l’Evêché à Limoges. She has also taught the restoration of enamels
at the Institut National du Patrimoine for ten years. Ms. Beillard has participated in many
lectures and publications on the study and treatment of enamels.
35
36
CONCEPTION AND MAKING OF A “DISPLAY BOX” ADAPTED TO THE
CONSERVATION OF TWO PAINTED ENAMELS OF THE LOUVRE
FRANÇOISE BARBE
ABSTRACT – The Musée du Louvre, Paris, recently agreed to loan two Limoges enamels with
unstable glass composition to an exhibition being held in France and the United States. Because
of the sensitivity of these objects to environmental fluctuations, a specific microclimate box was
designed for their safe travel and display. The aim of this lecture is to give a precise description
and present images illustrating the fabrication of the microclimate box, and the decision-making
behind this project.
INTRODUCTION
The exhibition, France 1500: Between the Middle Ages and the Renaissance, organized by the
Réunion des Musées Nationaux and the Art Institute of Chicago, opened on October 4, 2010 in
Paris (and February 2011 in Chicago). This exhibition presented the opportunity to conceive,
make, and test a display box adapted for the preservation of two painted enamels of the Louvre
collection dated circa 1500 by the Master of the Louis XII Triptych: Plaque: The Virgin of Dolor
(30 x 21 cm, OA 11170) and Medallion: The Coronation of the Virgin (23 cm, N 1218).
These two enamels were to be loaned only to the Parisian venue, and the conception and
the making of this display box was a condition of the loan of these works for the exhibition.
Thanks to the studies made by Isabelle Biron at the C2RMF in Paris, as well as others, it appears
that the early painted enamels (late fifteenth to early sixteenth century) have an unstable
chemical composition, which explains their elevated sensitivity to climate fluctuations. Some
enamel colors are especially problematic, particularly the blue, mulberry (lie de vin), and violet.
The two plaques by the Master of the Louis XII Triptych have shown signs of deterioration, even
in the permanent display case of the Louvre, due to various reactions to climate fluctuations.
37
Françoise Barbe
Conception and Making of a “ Display Box” for Two Painted Enamels of the Louvre
Most recently, in January 2010 during the beginning stages of this project, the relative humidity
(RH) was 55% in the exhibition case, which is far higher than the 40–42% recommended by Ms.
Biron for these enamels.
DISCUSSION
The Louvre obtained financial support from the Réunion des Musées Nationaux to employ the
most appropriate person to conceive and realize the microclimate box. The difficulty was to
successfully make a display box that met both the conservation parameters, as well as the
aesthetic ones. In France, two conservators specialize in fabricating microclimate boxes for
paintings on wood: Daniel Jaunard and Patrick Mandron. After explaining to them the context of
this project, in December 2009, Daniel Jaunard agreed to participate.
For a panel painting, the main purpose of a sealed enclosure is to maintain an RH
typically around 55%. Good results are given with this method—even if there is no silica gel in
the enclosure—and can be adapted for other two dimensional objects, in this case enameled
plaques. The most important factor is to create an enclosure that is completely airtight in order to
maintain the correct microenvironment inside. The difference between recommended
environmental conditions for a painting versus an enamel is the RH should be around 40–42%
for an enamel. It was decided to create an airtight box containing silica gel conditioned to 40%
RH and to have a trial period before the beginning of the exhibition. The interior climate of the
box was checked regularly by the Louvre conservation department using a small electronic
thermo-hygrometer (Hanwell), accessed on the exterior by a small USB port on the side of the
box. The size and the color of the microclimate box for the two enamels was based on the idea of
exhibiting the works in this enclosure in the permanent display case at the Louvre, upon their
return in January 2011.
The following is a basic technical description of the microclimate box:
•
Size (horizontal): 44 x 63 cm
•
Main structure (frame): constructed using maple wood with a compartment on the back
devoted to receive the silica gel
38
•
Interior backing board: solid panel of basswood (eliminates problems with formaldehyde
or poor adhesives, i.e. plywood, but not shrinkage) and a narrow slot around the
perimeter to provide air movement inside the box
•
Glazing: clear acrylic sheet 5 mm thick (Plexiglas®)
•
Exterior backing board: solid aluminum sheet metal to seal the box on the back and keep
it airtight
•
Other details:
- Gaps between the aluminum backing, frame, and acrylic sheet were sealed with
aluminum foil tape
- Acrylic and casein paint (Emery & Cie®) used on interior and exterior of box
- Custom brass mounts coated with acrylic resin where in contact with the enamels
- Silica gel conditioned to 40% (Prosorb®)
CONCLUSION
The enamels are on display, but due to the time constraints of the project, the results of the
testing period have not been interpreted yet and there are still questions to be answered. For
instance: How long will the box maintain 40% RH and will the silica gel need to be changed?
The box was tested prior to installing the enamels and after two days the interior was conditioned
to 40%. The enamels were installed in the new display box just before installation. The enamels
and the microclimate box will continue to be monitored throughout the exhibition. When the
enamel plaques return to the Louvre their condition will be evaluated to determine if the display
box can be used for their permanent exhibition in the museum.
AUTHOR
FRANÇOISE BARBE, CURATOR
Département des Objets d'art, Musée du Louvre, 101 rue de Rivoli, 75058, Paris, cedex 01, tel.
00 33 1 40 20 50 34, fax 00 33 1 40 20 52 81, [email protected]
Françoise Barbe is Curator in the Department of Objects at the Musée du Louvre where, since
2008, she has overseen the collections of Renaissance ceramics and painted enamels. She
received her undergraduate and graduate degrees from the École du Louvre. After an MA at the
University of Paris I Panthéon-Sorbonne, she joined in 1997 the National Heritage Institute and
graduated in 1998 as curator in charge of the sculptures, books, and objets d'art from the Middle
Ages and the Renaissance at the Petit Palais, Musée des Beaux-Arts in the City of Paris. She
currently works closely with enamels conservator, Béatrice Beillard, and senior research scientist
and engineer, Isabelle Biron, of the Centre de Recherche et de Restauration des Musées de
39
Françoise Barbe
Conception and Making of a “ Display Box” for Two Painted Enamels of the Louvre
France, in researching painted enamels of Limoges. This collaboration began while organizing
an exhibition on painted enamels at the Musée de l’Évêché de Limoges in 2002 with their
Director, Véronique Notin, entitled “La Rencontre des Héros: Regards Croisés sur les Emaux
Peints de la Renaissance appartenant aux Collections du Petit Palais, Musée des Beaux-Arts de la
Ville de Paris et du Musée de l'Évêché de Limoges.”
40
41
PREVENTIVE CONSERVATION OF LIMOGES ENAMELS
DAVID THICKETT AND JENNY STUDER
ABSTRACT – This study reports on an investigation of the environmental parameters for the
display of the Wernher Collection at English Heritage’s Ranger’s House in Greenwich Park,
Great Britain. This collection is part of a hundred year loan, which includes an important corpus
of Limoges enamels. As reported at the first Experts’ Meeting in 2006, tungsten lighting has
been found to cause significant temperature distributions within showcases. The risk from such
medium scale heating events is not easy to assess; therefore acoustic emission technique was
used to detect micro damage within enamels. In addition, the performance of current methods to
control relative humidity, the air exchange rate, and the risks from carbonyl pollutants within the
showcases were also assessed. This analysis resulted in several changes to improve the display
microenvironment.
INTRODUCTION
The diamond magnate Julius Wernher (1850–1912) had a passion for medieval and Renaissance
art and amassed the finest corpus collected in the twentieth century. He displayed his outstanding
collection of paintings, bronzes, majolica, and Limoges enamels in his London residence, Bath
House, in specially constructed showcases. In 2000 the Werner foundation signed a 100-year
loan with English Heritage to display this material to the public at Ranger’s House. In a
£2,000,000 project, the ground floor was transformed into an historic interior, while the upper
floor displayed the objects in showcases reproducing Wernher’s early twentieth-century ornate
cases. Two original showcases were reused and refitted to modern standards and fifteen new
cases installed. The relative humidity (RH) in the cases was controlled with conditioned silica
gel (Artsorb) hidden within the display plinths. The RH requirement for glass was the
42
dominating parameter, and the range was set at 35–40% following the work of Ryan (1996). The
copper supports for the enamels also required a low RH to retard corrosion, but 40% is more than
adequate in the relatively unpolluted atmosphere of the Ranger’s House. The initial
specifications for temperature increase inside the cases was set at less than 5ºC, however the
tungsten lighting used in the top of the showcases induced a daily temperature increase of 4–7ºC
depending on the location of the enamel plaque in the case. This translated to a 2.5ºC
temperature range across the surface of the enamels displayed higher in the cases. It was unclear
whether such temperature fluctuations posed a risk to the enamels and research was initiated.
ACOUSTIC EMISSION TECHNIQUE
Recent studies on the effects of temperature rise on showcase air exchange rate have shown that
a 5ºC increase is far too high and a modern specification should be closer to 2ºC. The evidential
background for temperature specifications for enamels is incomplete with only one reported
instance of damage published with temperature measurements—this was spalling of a Limoges
enamel plaque on silver after a 10ºC temperature drop. There are several anecdotal reports of
damage but no supporting temperature measurements, making specification difficult. The risk
from such medium scale heating events is not easy to assess, even with microscopy. Observing
the harmful changes that can occur between the enamel and metal interface is difficult; therefore
acoustic emission has been developed and validated for use on enamels. The technique uses
sensors applied to the surface of the object to detect the high frequency noise emitted when
brittle materials undergo micro-cracking. It has been used in conservation for monitoring damage
on wood, copper alloys, and from salt activity in limestone, for measuring the acoustic emission
from stress damage that is not visible to the human eye (Grossi et al. 1997; Caneva et al. 2004;
Jakiela et al. 2007, 2008).
Tests were performed on pre-damaged replica enamels (kindly supplied by Veerle Van
der Linden and Eva Annys). The coupling of the acoustic emission sensors (Physical Acoustics
R15A running onto a Pocket AE-2) applied to these samples was optimized to increase the
signal. The samples were then partially immersed in a hot water bath and deformed with three
point bend tests and the amount of acoustic emission recorded. Three point bend tests were used
because the shape of the enamel plaques were curved (due to their production method) and laser
interferometry measurements (Schmitt Acuity AR200) indicated an increase in curvature giving
43
Thickett and Studer
Preventative Conservation of Limoges Enamels
a deformation of 30µm when the lights were on in the showcases. These experiments
demonstrated that the method was sufficiently sensitive to be applied to enamels and pressing the
sensor onto the glass surface gave enough coupling to acquire acoustic emission signals. The
experiments also verified that the acoustic emission signals were originating from the glass or
glass metal interface and not from the copper.
Four series of measurements were undertaken on the enamel plaques located in different
showcases thought to be most at risk from the highest temperature increases observed. All these
measurements recorded acoustic emission events from the enamels when the lights were turned
on and heated up. This evidence was used to bid for funds to replace the tungsten lamps with
light-emitting diodes (LED). The LED lamps were found to have under 25% of the near infra-red
emission of the original tungsten lamps. The color rendering indices of the LEDs (Philips Master
MR16LV – 4WGUS ) were measured and curatorial opinion was that they were of sufficient
quality. Tests with multiple high precision temperature and RH sensors in cases with the new
LED lighting showed temperature rises of less than 1.4ºC and no acoustic emission events.
RELATIVE HUMIDTY
The RH control capacity of a showcase depends on its air exchange rate, the loading and type of
adsorbent, and how often operationally the adsorbent can be changed. One of the showcases with
Limoges enamels had shown a dramatic increase in air exchange rate over the five years since
installation: from 0.5 per day (well under the original specification of 1.0 per day) to over 3.7 per
day. As the space for silica gel was limited by the display plinth, this meant the case could no
longer hold its specified RH conditions. The Artsorb was replaced initially with Prosorb and then
with Rhapid gel. These gels have increasing buffering capacity in the desired RH range. With
Rhapid gel the RH conditions were retained.
POLLUTANTS
Particular glass formulations are known to deteriorate more rapidly in the presence of certain
concentrations of the carbonyl pollutants methanal (formadehyde) or methanoic (formic) acid
(Robinet 2005). The water-based coating Dacrylate 103 applied to the medium-density
fiberboard (MDF) used in the interior of the showcases is known to retard emission of methanal
but not methanoic acid to any significant degree (Thickett 1998). Ethanoic (acetic) and
44
methanoic acid are known to accelerate the corrosion of copper, but only at much higher
concentrations. Methanal is also reported to accelerate the corrosion of copper but only at a RH
significantly in excess of the 40% as an upper limit in the enamel showcases. The carbonyl
pollutant concentrations in the Limoges showcases were measured using diffusion tubes. The
concentrations were well below the reported damage levels for either glass or copper.
Concentrations were higher in shallower cases because of the higher surface to volume ratio of
the coated MDF. The silica gel is probably also having a beneficial effect of adsorbing some of
the ethanoic and methanoic acid and methanal (Grosjean and Parmar 1991). The reconditioning
of the gel at 35ºC was observed to cause emission of ethanoic and methanoic acid (methanal was
not measured). Similar measurements in showcases at Apsley House, with enameled batons
exhibiting ongoing deterioration, detected concentrations of methanoic acid above the reported
damage threshold. These cases were constructed of wood and were very shallow with no silica
gel. Activated charcoal cloth was added beneath the display fabric covering the backboard. This
was positioned carefully so as not to touch the silver objects, as the cloth contains chloride which
can rapidly accelerate corrosion in direct contact with the object. The measured levels of
methanoic acid reduced by over 80% and dropped well below the threshold.
CONCLUSION
The reported actions have improved the preventive conservation of an important collection of
Limoges enamels, thus ensuring their continued benefit to the public and protecting the generous
loan from the Wernher Collection for the future. The acoustic emission work has provided a
basis for thermal specifications for fused glass on metal substrates, and the study supports the
ongoing evaluation of microenvironments for sealed display cases and the specifications for their
environmental parameters.
REFERENCES
Caneva, C., A. Pampallona, and S. Viskovic. 2004. Acoustic emission to assess the structural
condition of bronze statues. Case of the “Nike” of Brescia. 26th European Conference on
Acoustic Emission Testing. Berlin, September 15–17. 567–574.
Grosjean, D. and S. S. Parmar. 1991. Removal of air pollutant mixtures from museum display
cases. Studies in Conservation 36(3):129–141.
45
Thickett and Studer
Preventative Conservation of Limoges Enamels
Grossi, C. M., R. M. Esbert, L. M. Suárez del Río, M. Montoto, and M. Laurenzi-Tabasso. 1997.
Acoustic emission monitoring to study sodium sulphate cristallization in monumental porous
carbonate stones. Studies in Conservation 42:115–125.
Jakiela, S., L. Bratasz, and R. Kozlowski. 2007. Acoustic emission for tracing the evolution of
damage in wooden objects. Studies in Conservation 52:101–109.
Jakiela, S., L. Bratasz, and R. Kozlowski. 2008. Acoustic emission for tracing fracture intensity
in lime wood due to climatic variations. Wood Sci Technol 42:269–279.
Robinet, L., S. Fearn, and K. Eremin. 2005. Understanding glass deterioration in museum
collections: a multi-disciplinary approach. ICOM Committee for Conservation preprints. 14th
Triennial Meeting, The Hague. Paris: ICOM 1:139–145.
Studer, J. 2009. Investigations of the Application of Acoustic Emission Technique to Limoges
Enamels for Damage Assessment. Unpublished MA dissertation, Royal College of Art, London.
Ryan, J. L., D. S. Mcphail, V. L. Oakley, P. S. Rogers, and L. Victoria. 1996. Glass deterioration
in the museum environment: A study of the mechanisms of decay using secondary ion mass
spectrometry. ICOM Committee for Conservation preprints. 11th Triennial Meeting, Edinburgh.
Paris: ICOM 2:839–844.
Thickett, D. 1998. Sealing of MDF to prevent corrosive emissions. The Conservator 22:49–56.
ACKNOWLEDGMENTS
The authors would like to acknowledge the kind assistance of the Wernher Foundation, Annie
Kemkaran-Smith, Veerle Van der Linden and Eva Annys, Physical Acoustics, and Lorraine
Gibson for ethanoic and methanoic acid analyses.
AUTHORS
DAVID THICKETT, Senior Conservation Scientist, corresponding author
English Heritage, Rangers House, Chesterfield Walk, London, England, SE10 8QX, tel 07770
397964, fax 020 8853 8801, [email protected]
Mr. Thickett studied Natural Sciences at Cambridge University. He joined the British Museum
Conservation Research Team in 1990, where he was responsible for research into the
deterioration, conservation, and preservation issues surrounding glass, metals, and stone. During
his tenure at the British Museum he analyzed over one hundred enamels, both modern and
archaeological, investigating deterioration caused by environmental conditions. In 2003, Mr.
Thickett joined the Collections Conservation Team of English Heritage. He is a working group
chair and UK management committee member of COST–EnviArt, which focuses on the
chemical effects of the indoor environment on cultural heritage. He sits on the management
board and is the corrosion product spectra chief moderator for the Infra-red and Raman User
Group.
46
JENNY STUDER , Conservator and Collections Care Manager in Private Practice
Bruderbüelstrasse 14, 8332 Russikon, Switzerland tel. +41 44 954 05 28,
[email protected]
Mrs. Studer is a recent graduate of the Royal College of Art/Victoria & Albert Museum, London,
with a Master’s degree in Preventive Conservation for Heritage Collection Management. During
her graduate studies she focused on monitoring Limoges enamels with acoustic emission. She
worked as an archaeological conservator for several years for the Swiss National Museum and is
currently working as a consultant for museums in Switzerland.
47
48
WORKING ON A LARGE SCALE: CONSIDERATIONS FOR THE CONSERVATION
OF AN OUTDOOR ENAMEL MURAL
CÁTIA VIEGAS WESOLOWSKA
ABSTRACT – The Polish artist Stefan Knapp (1921–1996), was the first artist to use 0% carbon
steel as a substrate for enamel, allowing the possibility of making large panels for display as part
of an architectural design. One of his panels is mounted on the exterior of St. Anne’s College in
Oxford, UK, and was included as part of the complete structural building restoration plan. This
paper will focus on the artist’s materials and techniques, and the problems concerning the
conservation of this mural, which consists of large enamel on steel panels mounted outdoors.
INTRODUCTION
Conservation of contemporary art brings its own challenges. Some twentieth-century materials
are much more complex and diverse than most of those available in the past and artists are more
experimental in their use. When considering objects made of enamel on metal, one is accustomed
to working on small-scale works since the materials—typically glass on copper, silver, or gold—
dictate the final size. For instance, in the last Enamel Group meeting in Rome (2008) the author
presented a paper on the conservation of a group of fourteenth- and fifteenth-century translucent
enamels on silver from the V&A Museum. The pieces were mainly small plaques with
dimensions of approximately 4–6 square centimeters. A year later the author examined a
contemporary enamel mural in Oxford, and was amazed not only by the scale but also the
different enameling methods used. This mural measured 16 square meters, which was quite a
change from the earlier objects examined. These experiences represent two completely different
periods of enamel on metal: those of unknown authorship and manufactured by traditional
craftsmen, to the work of a twentieth-century artist who learned his methods through
experimentation.
49
Cáia Viegas Wesolowska
Working on a Large Scale
The artist and creator of the large scale enamel mural was Stefan Knapp. Born in 1921 in
Biłgoraj, Southern Poland, he was a man with an incredible past. From imprisonment in Siberia
in the late 1930s to being a pilot for the British Army during WWII, he kept many visual
memories of what he saw and went through—memories that were often captured in his artwork.
Knapp was one of those artists who challenged form and materials to achieve his artistic goals.
He became the initiator of enamel on steel work on a large scale, by experimenting first with
copper then steel as a substrate and applying jewelry and porcelain enamels, paint, and gold leaf,
among other materials. A fine art painter, Knapp studied in London and later made his studio
there, becoming involved with enamels almost by accident. The story goes, that he was admiring
an antique enamel piece of a friend and dropped it by accident cracking the enamel. Feeling
guilty about his clumsiness, Knapp set about finding out how to repair the object. It took him
several months of exploration and self-teaching, but he soon became captivated by the
permanency of the color and the unlimited possibilities of its use. He was the first artist to use
0% carbon steel as a substrate for enamel, allowing the possibility of making large panels which
were lighter, and cost less to produce, than the previous enamels on copper substrate. His large
panels can be seen in the United States, the United Kingdom, and Poland, and are mainly
displayed as part of an architectural design.
The mural under discussion was thought to have been made in the late 1950s for the
exterior of St. Anne’s College in Oxford. As part of a complete structural building restoration the
panels were included for conservation. In 2009, after leaving the V&A Museum to move
permanently to Poland, the author was asked to produce a condition report for the work. Excited
at the prospect as it appeared that the artist was Polish and lived in London, and the author had
just moved to Poland from London, it felt that it was in the stars to accept flying to Oxford to
examine the mural. Unfortunately the funding for the project was delayed, which is not
uncommon for large conservation projects, particularly in the midst of an economic crash.
Conservation of the building and the mural is currently re-scheduled for 2012, allowing extra
time for research. This paper will therefore focus on the work of the artist and the problems
concerning the conservation of large, outdoor enamel on steel panels and the development of a
practical treatment plan.
50
STEFAN KNAPP AND ENAMELING IN LARGE SCALE
Enameling in large scale commenced in the mid 1950s for Knapp. With his studio outside
London capable of housing a kiln, designed by him, large enough to fire panels up to 3 meters in
length and over 1 meter in width. It was here that he started to experiment and create enamel on
steel plaques unprecedented in size. In 1958 he was commissioned to make 17 murals for the
Heathrow airport, which can still be seen today. He also made murals for the Warsaw
underground station and for Torun in Poland to celebrate the 500th anniversary of the birth of
Nicolas Copernicus, among others. His largest work, and thought to be the largest enamel mural
in the world, was commissioned for the Alexander building in Paramus, New Jersey;
unfortunately it is no longer there but will hopefully be displayed at the Bergen Museum of Art
and Sciences, Paramus, New Jersey soon.
There are positive aspects from the point of view of researchers and conservators when
working on pieces by contemporary artists, namely the possibility of having personal contact
with the artist to discuss their methods. But not all artists are keen to share this information, and
those who unfortunately are not with us anymore, such as the case of Knapp, usually leave little
documentation. Fortunately, the artist’s wife, Cathy Knapp, who currently maintains an art
gallery in the UK and exhibits some of her husband’s work, was able to provide some
information on his working methods. She is also an enameller and worked with Knapp at the
later stage of his life.
CONSERVATION
The mural at St. Anne’s College, Oxford is a set of four panels totaling 16 square meters. Each
panel is slightly bowed in shape to follow the contour of the wall on which it is mounted; and
each panel is folded at the edges. The panels are made of steel and enameled with a variety of
finely powdered glasses using different techniques. There is also the addition of gold leaf in
small areas of the enamel. The mural is signed by the artist in the glass, but is not dated.
By 1957 Knapp was using 0% carbon steel which he cleaned chemically, washed, and
quickly sprayed with a commercially produced cobalt enamel grip coat. This was a pale grey
biscuit color before firing, but after an initial firing at 820ºC, became a shiny black color. He
then poured a coating of opaque white enamel over the panel and when it was dry would draw
his cartoon, sgrafitto style, using a metal scribe. He would position each panel in its final
51
Cáia Viegas Wesolowska
Working on a Large Scale
arrangement to ensure the continuity of his design before drawing the composition. Some of his
panels were counter enameled to prevent warping. It is currently impossible to ascertain if this is
the case with St. Anne’s mural, as it hasn’t been removed from the wall.
When considering the conservation of the mural there were several important issues: First
and foremost is the condition of the work and identifying the problems that need to be addressed
for the metal substrate and enamel. Next is developing a suitable conservation plan that is
appropriate for a large enamel work on steel. There are several factors that may limit what can be
done, foremost the environmental factor. The mural is displayed on the exterior of a building and
is subjected to outdoor conditions. It is also located in a position where it can be touched or
tampered with by the public. Finally the support for the work, which includes the concrete walls
and the backing for the panels, needs to be protected and the mounting system evaluated to
ensure that the panels are securely anchored to the building.
Preliminary examination of the mural was undertaken in 2009, however, because the
panels were still attached to the exterior wall, the reverse could not be assessed. It should be
noted that it is known that the artist applied asbestos panels behind some of his large-scale
works, but this was not possible to ascertain at the time. Health and safety measures would be
implemented if asbestos were found to be present. Enamel loss and lifting around edges of the
panels were found and resulted in extensive iron corrosion along the edges of enamel loss.
Surface accretions and dirt were found overall. Surface staining caused by moisture and iron
corrosion caused vertical lines to develop on the top area and on the lower border resulting in
chemical and aesthetic damage. (Additional comments on the condition of the panel are
discussed in the presentation with a video of the enamel mural).
A preliminary conservation proposal has been developed, and the author is researching
suitable conservation materials for the treatment of the mural. Analysis of the enamels is not
currently possible, but may not be necessary for evaluating the condition. The enamel has not
deteriorated, and the foremost damage appears to be to the metal substrate. One of the main
concerns is the removal of the corrosion stains beneath the enamel. They appear to come from
behind the panel rather than from the front. Proposing a comprehensive treatment plan of the
mural, however, is limited by the fact that it is not in full view and therefore a complete
diagnosis cannot be established.
52
CONCLUSION
It has been interesting to study the work of a contemporary artist, and to begin the necessary
research into other examples of his work, in an attempt to compile information about his
techniques and materials. This will hopefully benefit future conservators and researchers who
may be faced with conserving a similar work. Enameling on steel allowed Knapp to finally find a
method for creating a lasting statement of his work through the permanency and vibrancy that
fused glass on metal is able to offer. Unfortunately, nature is a strong force, and can inevitably
deteriorate even the strongest materials. The enamels that Knapp used continue to be permanent
on the St. Anne mural, but the metal substrate has suffered from exposure to over 50 years of
outdoor environmental conditions and the affects are clearly visible today.
ACKNOWLEDGMENTS
The author would like to thank Cathy Knapp for sharing her thoughts and memories on Stefan
Knapp and his work.
AUTHOR
CÁTIA VIEGAS WESOLOWSKA, Historical Metals Conservator in Private Practice
Gdansk, Poland, tel. or fax +48 58 7185450, [email protected]
Cátia Viegas Wesolowska is currently working as a freelance conservator in Poland. From 2003
to 2009 she was initially Metals Conservator and later Senior Metals Conservator at the Victoria
and Albert Museum in London. Ms. Wesolowska trained in jewelry and silversmithing prior to
completing a BSc(Hons) in Conservation of decorative surfaces and a postgraduate diploma in
the Conservation and Restoration of Fine Metalwork at West Dean College, Great Britain. She
worked as a freelance conservator in Buenos Aires, Argentina for four years, working on the
conservation of the main Cathedral and La Prensa building. At the V&A, she was involved in
various temporary and permanent exhibitions related to the collections in the Gothic Sculpture,
Sacred Silver, Sculpture, Jewelry, and Medieval and Renaissance galleries. She has a particular
interest in conservation and technological aspects of medieval enamels on silver and early
medieval copper alloys. She has lectured and published on her specialist subjects, presenting a
talk entitled “Translucent Enamels on Silver: Examination of the Metal Substrate on a Group of
European Fourteenth- and Fifteenth-century Objects,” at the last biennial Experts’ Meeting on
Enamel Conservation in Rome. Current research includes the Gloucester candlestick and mounts
on ivories of al-Andalus from the V&A, the first of which was recently presented in 2010 at the
V&A conference “Revealing Medieval and Renaissance Europe: Makers and Markets 11001600”, and the second in Krakow at the conference “The Art of Islamic World”.
53
54
A CONCISE BIBLIOGRAPHY ON THE TECHNOLOGY, DETERIORATION, AND
CONSERVATION OF ENAMELS ON METAL
AGNÈS GALL ORTLIK
ABSTRACT – The bibliography presented at the Frick Collection during the 3rd Expert’s
Meeting on Enamel on Metal Conservation, October, 2010 is an updated version of the first text
compiled and published in June 2001. It now consists of 327 references related to the
technology, deterioration, and conservation of enamels on metal. This presentation will discuss
some of the new resources used and the changes in technology that have helped to increase the
citations listed in the current edition.
INTRODUCTION
The Concise Bibliography on the Technology, Deterioration, and Conservation, of Enamels on
Metal (Gall Ortlik 2010) was initially the result of the author’s personal experience: While
carrying out the conservation treatment of two enamels on metal in 1999, she realized that it was
hard to find information related to the field of enamel on metal conservation. There were very
few articles dealing with this issue and they were often scattered in various sources not directly
connected to the conservation world—manuals, industrial magazines, art publications,
congresses, etc. The author took advantage of a one-year research internship at the Corning
Museum of Glass, New York, in 2001 and a year of scholarship at the Villa Medici in Rome in
2007 to collect the majority of the references presented in this bibliography. The text is mainly
geared towards objects' conservators who need to learn more about enamels on metal. It contains
only published sources and excludes classical literature on the conservation of glass and metal,
because it is considered that it is already known by the reader. The emphasis is in conservation,
but the work also includes the technology and the deterioration of these composite objects.
55
Gall Ortlik
A Concise Bibliography on the Technology, Deterioration, and Conservation of Enamels on Metal
Although there is a lot of articles on the history and technology of enamels, only the most useful
to a conservator have been selected here.
PRINCIPLE SOURCES AND UPDATES
The principal sources consulted during the initial research were the Art Index (1929–1994), the
Art and Archaeology Technical Abstracts (1967–1999), the Repertory of the Literature of Art
(Rinehart 1975–1989), the Bibliography of the History of Art (1991–1999), and the bibliography
of Jane Tudor (1994). The libraries used for the first edition were located in the Département des
Restaurateurs at the Institut National du Patrimoine (INP), Paris and the Rakow Library,
Corning, NY. For this new 2010 edition, the complete research includes the library of the
International Centre for the Study of the Preservation and Restoration of Cultural Property
(ICCROM), Rome.
The first version of this bibliography was edited in 2001 and presented to the Enamel
Group at its first meeting in Germolles, France in 2006. It was then also made available through
the ICOM-CC Glass and Ceramic and Metal Working Groups webpages. In comparison with the
2001 version, this new one has been enriched with 156 references. For published works after
2000: there are 99 that deal with conservation; 8 resources on defects and deterioration; 45 on
technology; and 5 concerning historical manuals. The Enamel Group has significantly
contributed and helped to increase the number of references, by making available through the
ICOM-CC webpage the abstracts of the papers presented during the Expert’s meetings since
2008. The Italian citations are now better represented, because a lot of the papers were difficult
to access without going directly to the source. Doctoral theses, even if not published, have also
been added, specifically an important one in Italian and one in Spanish. Internet has greatly
evolved in this last decade as well: in 2001, while looking for enamel conservation resources on
the web, only one reference could be located. In 2010, numerous and valuable information
related to enamel on metal conservation can be found, including translated papers from rare
languages or digitized antique books, for instance, one found on Google Books: Bulletins de la
Société scientifique, historique et archéologique de la Corrèze (1985). This way of collecting
resources will need to be seriously taken into account for the next edition of this bibliography.
56
CONCLUSION
The compilation of references is a never-ending story and bibliographers know that all one-time
bibliographies share the same problem—they are outdated the very same day of their edition. For
this reason, all professionals that know references that are not listed in this compilation are
encouraged to communicate them to the author of this bibliography, so that they can be added to
the list and benefit the conservation community as a whole as well as the enamels that are under
their care.
REFERENCES
Art and Archaeology Technical Abstracts. 1967–1999. London: IIC.
Art Index. 1929–1994. New York, NY: The H.W. Wilson Company.
Bibliography of the History of Art. 1991–1999. Vandoeuvre-les-Nancy: Institut de l'Information
Scientifique et Technique (INIST)-CNRS (1991–2007) and Santa Monica: The Getty Research
Institute (GRI) (1991–2010).
Bulletins de la Société scientifique, historique et archéologique de la Corrèze. 1985. v7.
Rinehart, M. ed. 1975–1989 International Repertory of the Literature of Art. Sterling and
Francine Clark Art Institute, New York: Volt Information Services.
Tudor, J. 1994. Vitreous Enamels. A Bibliography of Processes, Objects and Enamelists,
Edgewood, WA: Jane Tudor.
AUTHOR
Agnès Gall Ortlik, conservator in private practice
COREBARNA S. L., Mare de Déu dels desemparats 5, 1r 5a, 08012 Barcelona, Spain
Ms. Gall Ortlik is a conservator specialized in Fire Arts conservation (ceramic, glass, and enamel
on metal). She graduated in 2000 from the Institut National du Patrimoine (Paris, France) and
lives today in Barcelona, Spain, and works as a free-lance conservator in Europe for institutions
and private clients. She has worked, among others, for the National Museum of Art of Catalonia,
the Vatican Museums, and the Renaissance Museum in Paris. She has a special interest in the
conservation of enamels on metal, and with the goal of fully understanding their techniques and
materials. She graduated in the art of enameling at the Llotja School of Art and Design in
Barcelona in 2006. She is a European delegate of the Catalan Professional Conservators’
Association (named Grup Tècnic) at the European Federation of Conservator’s Associations
(ECCO) and, since 2008, coordinator of the Enamel Group of the ICOM-CC Glass and Ceramics
WG.
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58
JAPANESE CLOISONNÉ ENAMELING ON GLASS SUBSTRATE, LATE
NINETEENTH CENTURY TO THE PRESENT
FREDRIC T. SCHNEIDER
ABSTRACT – This lecture will trace the 130-year history, from the late 1870s to the present, of
cloisonné enameling on glass substrate in Japan; discuss the artists involved; and present
examples. It will describe the manufacturing process and explain the variations in cloisonné
technique on other substrates required to accommodate the properties of glass. It will also
distinguish Japanese cloisonné on glass from Japanese plique-à-jour.
INTRODUCTION
Modern Japanese cloisonné enameling began in the 1830s when one man in Nagoya, Kaji
Tsunekichi (1803–83), discovered the secrets of making enamels by taking apart a Chinese
example. He created his own works and took on apprentices who in turn had their own
apprentices, often family members, creating a direct lineage that by the 1880s spread throughout
Japan. In the late nineteenth and early twentieth centuries Japanese cloisonné enameling was
frequently said to be the finest in the world and included a wide variety of techniques to achieve
varying aesthetic effects. Although the vast majority of Japanese cloisonné was on metal
substrates, they also employed glass, porcelain, and lower fired ceramics as a base. Glass,
however, proved to be the most difficult.
The following description of the Japanese cloisonné on metal process is illustrated in
stereographic photographs produced in the first decade of the twentieth century (now in the
author’s collection). The metal substrate, usually of copper, is formed into the desired shape and
the design is either drawn on or engraved into the surface (fig. 1).
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Schneider
Japanese Cloisonné Enameling on Glass Substrate, Late Nineteenth Century to the Present
Fig. 1. Hammering metal substrate to shape, ca. 1904, stereographic photograph, author’s
collection. Photograph © Fredric T. Schneider.
Thin flattened wires of copper, copper alloys, silver, or gold, are individually cut to size, formed
into the correct shape, and glued on edge to the metal surface (fig. 2). A thin coating of low-fired
powdered enamel or powdered metal is spread over the surface and the object is fired for the first
time to permanently affix the wires. Next, slightly moistened finely-powdered enamels, which
were previously prepared at over 1300ºC, are carefully applied among the wires (fig.3). The
piece is then fired a second time at approximately 800ºC to fuse the enamels to the metal
substrate (fig. 4). The sequence of filling the cells with powder and refiring is repeated multiple
times until the fired enamel is raised slightly above the cell walls. Then grinding begins, utilizing
about a dozen increasingly fine abrasives until the enamels are ground flush with the height of
the wires (fig. 5). Polishing achieves the ultimate mirror finish. The wires may be gilded, and
usually metal rims, most frequently of brass or silver, are added to the top and bottom or edges of
the object.
60
Fig. 2. Attaching wires to metal substrate, ca. 1904, stereographic photograph, author’s
Fig. 3. Inserting powdered enamels among wires, ca. 1904, stereographic photograph, author’s
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Schneider
Fig. 4. Preparing to fire a large cloisonné-enameled vase, stereographic photograph, author’s
Fig. 5. Grinding the enamels, ca. 1904, stereographic photograph, author’s collection. Photograph
© Fredric T. Schneider.
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JAPANESE CLOISONNÉ ON CERAMIC SUBSTRATE
When ceramic was the substrate, the process of creating cloisonné in Japan was for the most part
similar to metal (fig. 6). The great English designer Christopher Dresser (1834–1904) said he had
“observed every detail of the process” during his 1876–7 trip to Japan and reported, “in all
respects this manufacture resembles that of cloisonné metal objects, save in the fixing of the
wires to earth instead of soldering them to metal.” Likewise, the German chemist Gottfried
Wagener (1831–92), who aided in the development of Japanese enameling by introducing
advanced European technology in the 1870s, wrote in 1876 that the process was similar to that
used for metal. They and other early authors fail to mention the most significant difference from
the manufacture of metal-substrate cloisonné—time required in the kiln. Metal-substrate enamels
can be inserted cold into an already pre-heated 800ºC kiln and then removed into cool air a few
minutes later.
Fig. 6. Square box with lid, cloisonné on porcelain, Takeuchi Chūbei, ca. 1877, Japan, 7.7 x 9.5 x
9.5 cm, author’s collection. Photograph © Fredric T. Schneider.
Ceramic-substrate cloisonné, to the contrary, requires the long warm-up and cool-down periods
normal to almost all ceramic production, but is further complicated by the multiple firings
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Schneider
necessary for cloisonné work. The Japanese, who had a centuries-long history developing diverse
and superb ceramics, mastered the art of cloisonné on ceramic substrate quite quickly, producing
examples by the mid 1860s and making large quantities by the 1870s, when it was aggressively
shown and sold at domestic and international expositions.
JAPANESE CLOISONNÉ ON GLASS SUBSTRATE
In Japanese, glass-substrate cloisonné is known as garasutai jippō (glass-body enamel) (fig. 7).
Intuitively, it might seem easier to successfully adhere enamels separated by wires to a
chemically- and structurally-related glass surface, rather than to a metal substrate; however, this
is not the case. The somewhat different chemical make-up of the underlying glass versus that of
the enamels used in manufacturing cloisonné, and the higher coefficient of expansion and greater
mobility when heated compared to metal, make glass a far more difficult medium to use as a
substrate. Glass—like ceramic—requires slow build up of temperature and lengthy cooling down
in the kiln. Cracking and breakage occur during this cooling period (and sometimes during
heating), thus wasting a significant percentage; the larger the piece the more likely to crack or
break. In addition, when reheated, glass will often slump, distorting it often to the point of total
disfigurement.
Fig. 7. Bowl, cloisonné on glass, Mrs. Inaba Hiroyuki, ca. 1986, Japan, 7.6 x 12.3 cm, author’s
64
The great Japanese master enameler, Takeuchi Chūbei (1852–1922), was the first to make
garasutai jippō. This was an exceptional achievement at any date, especially at the time of his
innovation. Takeuchi first exhibited cloisonné on glass at Nagoya in 1878, and then a pair of
footed cloisonné on glass cups, now in the Tokyo National Museum, was shown at the 1881
Second Domestic Exposition. The pair has opaque enamel over the glass, rather than later
masters’ transparent or translucent enamel that takes better aesthetic advantage of the
transparency of the glass substrate. Takeuchi was one of the most prolific early makers of
cloisonné on ceramic. Ceramic and glass substrates present two of the same important challenges
to the cloisonné-enameler—a significant difference in their coefficients of expansion from that of
enamel and their need for slow heat build up and cooling off in the kiln. Takeuchi’s extensive
experience overcoming those difficulties in ceramic cloisonné must have been critical in helping
him solve the same problems with glass. His exposure to Gottfried Wagener, whose expertise
included glass as well as enamels, was probably instrumental in Takeuchi’s success at such an
early date. He subsequently won a bronze medal at the Paris 1889 exposition, probably for
metal-substrate work, but there is no evidence he continued his work on glass substrate after
1881.
After an over thirty year hiatus, a second early Japanese enameler, Tsunekawa Aisaburō
(1879–1946), managed to successfully create cloisonné on glass. Tsunekawa apprenticed in
Nagoya, then went to Kobe in 1897, and finally returned to Nagoya in 1904–5. According to
Tsunekawa’s son, his father pursued cloisonné on glass from 1914 to 1921, probably taking most
of that period to perfect his technique. By 1921 he abandoned glass substrate to save himself
financially, frustrated by the difficulties of manufacture and presumably by the small demand for
what must have been an incredibly expensive item, and whose price had to reflect the immense
effort and numerous wasters.
During recent years, progress has once again been made in producing cloisonné on glass,
this time in Kyoto. Mrs. Inaba Hiroyuki (b.19??) of the Inaba Cloisonné Company made glasssubstrate cloisonné pieces during the 1980s and early 1990s (see figs. 7, 9) but abandoned
production because of the immense effort involved and kiln breakage of thirty per cent. Two
other makers in Kyoto have subsequently produced cloisonné on glass. Unlike the Meiji and
Taisho era masters who as far as is known deposited unmodified cloisonné-enamel powder on
typical commercial glass, the recent Japanese makers have succeeded by altering the chemical
65
Schneider
formula of either the glass substrate or the applied enamel so that they are more alike, thus
creating similar coefficients of expansion. The specific formulas are carefully guarded secrets. In
general, the contemporary process first requires making the glass substrate, usually in the form of
a cup, bowl, or plate, over a mold. The glass is fired upside down at varying temperatures
between 800–1000ºC specific to each maker. Very thin, pure-silver wires and enamels are then
added to the glass surface while the mold usually remains in place. The wires and enamels are
fired at temperatures about 100ºC lower than the glass. Each firing, as noted, requires a heat
build up and even longer cooling period to accommodate the glass substrate. An effort may be
made to apply all the colored enamel powders with one or two firings to reduce both the risk of
cracking and slumping, as well as the time and expense of further enameling-firing sequences.
The enamels and wires are then ground down level with each other and the mold is removed,
after which the piece is sometimes sandblasted to make it matte and translucent for aesthetic
reasons. As with plique-à-jour, after a piece is completed tensions can remain in its structure and
spontaneous cracks can subsequently emerge in an apparently perfect piece.
JAPANESE PLIQUE-À-JOUR
Japanese plique-à-jour, known in Japan as shōtai jippō (removed body enamel), was shown by
Namikawa Sōsuke (1847–1910) at the 1893 Chicago Columbian Exposition, and Henry Walters
(1848–1931) bought a superb example by him at the 1900 Paris Exposition Universelle now in
The Walters Art Museum, Baltimore. Sōsuke’s technique and the resultant appearance differ
from subsequent Japanese makers’ work; he produced his objects by carving out slivers of silver
from a thick silver bowl and then applying enamel powder into the narrow openings. It was not
until the first years of the twentieth century that the Japanese developed what became the
traditional method and appearance of Japanese plique-à-jour and began making it on a regular
basis (fig. 8). It was almost certainly made initially by Nagoya’s Andō Cloisonné Company. The
great master enameler Kawade Shibatarō (1856–1921), who headed Andō’s factory circa 1902–
10, was undoubtedly involved in its creation. Others, all in the Nagoya area, followed.
Until its final stages, Japanese shōtai technique is similar to the usual method of
manufacturing standard metal-substrate cloisonné, except that as a first step a primer layer of
clear enamel is applied to the copper substrate and fired before wiring. The wires are then
attached to the clear enamel ground layer—rather than directly to the metal substrate—and the
66
object is refired. Transparent or translucent colored enamels with a lower melting point are
applied among the wires above the primer layer and refired repeatedly in the normal sequence.
At each firing, great care is taken that the primer layer does not melt, in order to avoid the wires
sinking through to the underlying copper substrate.
Fig. 8. Vase, plique-à-jour, Kumeno Teitarō, ca. 1905, Japan, 15 x 9.4 cm, author’s collection.
Photograph © Fredric T. Schneider.
When the colored enamels have been piled to a height above the wires, the enamels are ground
level to the wire and given their ultimate polish, once again in the usual sequence. At that point,
additional steps are taken that are unique to the manufacture of shōtai, compared to other
Japanese cloisonné. A protective wax or lacquer coating is temporarily placed over the polished
external surface, and then nitric acid is used both to remove the inner metal substrate and also to
frost the interior or underside of the enamel to make the piece more uniformly translucent. Silver
or chrome rims are attached to finish the piece.
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Schneider
Fig. 9. Detail of figure 7, integral glass foot rim on bowl. Photograph © Fredric T. Schneider.
Fig. 10. Bowl, plique-à-jour, unknown maker, ca. 1915, Japan, 6.3 x 12.8 cm, author’s collection.
Detail of enameled-silver feet edged with silver. Photograph © Fredric T. Schneider.
68
CONCLUSION
To a casual observer, the resulting effect of garasutai jippō is similar to plique-à-jour, and can be
mistaken for it at first glance. In fact, their appearances differ in a number of ways. Most
notably, metal bottoms, rims, and feet are not attached to garasutai; instead the pieces stand on
an integral thick-glass foot rim or are footless (figs. 9,10). In addition, the glass substrate is
noticeably thicker than plique-à-jour and often slumps because it is unsupported in the kiln by a
metal core, so that a piece can be somewhat asymmetrical and vary in thickness.
REFERENCES
Coben, L. A., and D. C. Ferster. 1990. Japanese cloisonné: History, technique and appreciation.
First Tuttle Edn. Rutland, VT, and Tokyo: Charles A. Tuttle Company.
Dresser, C. 1882. Japan: Its Art, architecture and art manufactures. London: Longmans, Green
and Co. (Republished unabridged and unaltered in 1994 as The traditional arts and crafts of
Japan Mineola, NY: Dover Publications, Inc.)
Ogawa, M. 1999. Hōgyoku Shippō. Nagoya: Nagoya City Museum.
Schneider, F. T. 2010. The art of Japanese cloisonné enamel: History, techniques and artists,
1600 to the present. Jefferson, NC: McFarland Press.
Wagener, G. 1876. Descriptive notes. In International exhibition, 1876, official catalogue of the
Japanese section, and descriptive notes on the industry and agriculture of Japan, ed. The
Japanese Commission. Philadelphia: The Japanese Commission:37–127.
AUTHOR
DR. FREDRIC T. SCHNEIDER, Independent Scholar
New York City, NY, [email protected]
Dr. Schneider is an independent scholar and an expert on Japanese enamels. His book The Art of
Japanese Cloisonné Enamel: History, Techniques and Artists, 1600 to the Present will be
published by McFarland Press later in 2010. He has lectured at the two most recent triennial
meetings of the International Conference on Glass (XX in Kyoto and XXI in Strasbourg) and is a
member of the Enamel on Metals Conservation Network. He has also spoken on enamels at
numerous museums and universities in the United States, and at various venues in China, Japan,
and England. Dr. Schneider holds bachelor and doctorate degrees from Yale University.
69
70
FOOTED BOWL OR ONLY A BOWL? THE INVESTIGATION OF A
SEVENTEENTH-CENTURY LIMOGES PAINTED ENAMEL OBJECT
BIRGIT SCHWAHN
ABSTRACT – This paper focuses on the authentication of an enameled footed bowl owned by
the Museum für Angewandte Kunst in Cologne, Germany, and attributed to the Limoges
workshop of Jean Laudin (1616–1688) or Jacques I. Laudin (1627–1695). A multi-disciplinary
investigation including the fields of heraldry, art-history, art-technology, and examination
methods including µ-X-ray fluorescence spectroscropy, X-ray computed tomography, and
infrared reflectography lead to a reassessment of the object. In addition, prior restoration
materials were analyzed by Fourier transform infrared spectroscopy, gas chromatography–mass
spectrometry, and scanning electron microscopy with energy dispersive X-ray spectroscopy.
INTRODUCTION
Limoges painted enamels were highly appreciated and in much demand by nineteenth-century
collectors. To meet this need, it was common to not only restore and reassemble these objects,
but to construct entire pastiches of original or newly fabricated painted enamel pieces—the latter
being also accompanied by the revival of the Limoges painted enamel technique at that time (see
Caroselli 1993; Speel 1998, 92; Netzer 1999). In recent years, intensive research has been carried
out on the authentication of European and American Limoges painted enamel collections
resulting in important contributions—a major part being the instrumental analysis of enamel
compositions (see Biron 2002; Bronk and Röhrs 2002).
The Limoges enameled footed bowl in this study was acquired by the Museum für
Angewandte Kunst (MAK) in Cologne, Germany, in 1963 (fig. 1). Prior to this time the footed
bowl belonged to the Lückger private collection in Cologne; no additional information about the
object’s provenance, history, or date of entry into the Lückger collection is known (Brill 1964).
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Schwahn
Footed Bowl or Only a Bowl? The Investigation of a Seventeenth-Century Limoges Painted Enamel Object
Fig. 1. Footed bowl, attributed to Jean or Jacques I. Laudin, mid 17th c., Limoges,
approximately 9 x 24.5 cm, Museum für Angewandte Kunst, Cologne, inv. H 1210.
Fig. 2. Inside of bowl showing the coat of arms in the center and the surrounding grisaille
decoration (see fig. 1 for overall image).
72
The object consists of three elements: the bowl, the foot, and a circular plate that is inserted into
the foot. All three pieces are covered with translucent, dark mulberry enamel. In the center of the
bowl, there is a polychrome coat of arms with a crown and two crossing palm leaves;
surrounding this are allegorical scenes painted in grisaille-technique (fig. 2). The foot bears gold
decoration with the monogram “RC”, enclosed by a crown and two crossing palm leaves (fig. 3),
similar to the coat of arms on the bowl. Based on the signatures, the entire object has been
attributed to the workshop of Jean Laudin (1616–1688) or Jacques I. Laudin (1627–1695) and
dated to the middle of the seventeenth century.
Fig. 3. Detail of golden monogram on the foot captured in raking light.
PREVIOUS RESTORATION
A coating that was formerly applied over almost the entire object had lost adhesion and was
severely cracked with active flaking. While the coating on the bowl was uncolored, it was toned
with blackish pigments on the foot. Fourier transform infrared (FTIR) spectroscopy and gas
chromatography–mass spectrometry (GC-MS) identified the coating as bleached shellac with the
addition of a drying oil. Enamel losses on the bowl and the foot had been replaced by fills and
inpainting. Calcium sulfate and calcium carbonate materials, identified with microchemical tests,
were used in combination with an organic binder for the opaque white fills. Below these fills, an
initial gray colored primer layer had been applied to the copper base (fig. 4). Microchemical
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Schwahn
analysis and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEMEDX) identified the compounds of the primer layer as lead white and carbon black; the FTIR
spectrum bore similarities to the overall coating and indicated a resinous binding medium as the
main component. It is interesting to note that lead white-based primers were typically used in
European painting on copper supports since they inhibit the formation of copper corrosion
products and adhere well to the subsequent paint layers (Wehlte 1967, 398; Farnsworth 1977; for
properties of lead white-based films see also Gettens et al. 1993, 69). To the author’s knowledge,
primers based on lead pigments have not been previously identified or described for enamel
restoration. However, the author’s recent examination of a Limoges painted enamel at the
Herzog Anton Ulrich-Museum (HAUM) Brunswick (inv. Lim 83), Germany, revealed one
further example of lead white-primer used for restoration. Interestingly, it is known that this
restoration was carried out by a German painter called Carl Bourdet in 1884 (Müsch 2002, 265,
23). Further research on this topic may reveal whether the use of lead white-primer is a unique
technique of this restorer or whether it can be found more frequently on painted enamels.
Fig. 4. Detail (fig. 1) showing gray primer layer on the copper base of the foot used for prior
restoration.
As part of a recent conservation treatment at the MAK, the coating was removed from all
enamel surfaces revealing that the dark translucent enamels of the foot and bowl differ from each
74
other in several aspects. Through these observations, questions arose about the authenticity of the
assembly of the object. The ensuing partial removal of fills from the bottom of the bowl and the
foot revealed more details that questioned the authenticity, the most evident being the solder join
between the bowl and the foot. While Limoges painted enamel objects were typically assembled
mechanically with rivets or other means, the use of solder is common for nineteenth-century
restorations (Beillard 2002, 2007; Speel 2008, 156), as is the assembly of pieces that did not
belong together originally. Therefore, the authenticity of the assembly was considered to be
doubtful and a multi-disciplinary investigation on this topic was carried out.
THE BOWL
The underside of the bowl is signed in gold “Laudin Emaillieur au faubour de magnine à
Limoges”, while a small monogram “IL” is located on the right side and painted with metal
oxides. The grisaille scenes partly derive from prints after Étienne Delaune (see Thomas 1960,
19), which were a common source for enamellers of the sixteenth and seventeenth centuries. A
painted enamel candlestick with a very similar grisaille work that is attributed to Jacques I.
Laudin exists at the Taft Museum in Cincinnati, Ohio (Verdier 1995, 403; inv. 1931.293). The
coat of arms in the center of the bowl, which consists of a family emblem and of an emblem of a
commander of the Order of Malta, belonged to Alexandre de Costaing de Pusignan, who held
such an office in 1666 and in 1674–1677 (Thiou 2002, 55, 57). Underneath the dark translucent
enamel of the bowl, an initial ground layer of clear enamel is present, which is a common
fabrication method for this type of sixteenth- and seventeenth-century Limoges painted enamel.
Qualitative µ-X-ray fluorescence (µ-XRF) spectroscopy was carried out on several enamel areas
and there was no evidence indicating an origin later than the seventeenth century. Opaque leadtin-antimony-yellow enamel was identified in one of the emblems and in one of the palm leaves;
this is rare on Limoges painted enamels in general, but typical for works by the Laudins in the
seventeenth century. Furthermore, zinc was detected within these opaque yellow enamels, which
is also specific to works by the Laudins (Bronk and Röhrs 2002, 43). Surprisingly, four different
types of dark translucent enamel were identified on the bowl. Three of these types seem to have a
high lead content differing mainly in the amount of manganese, iron, and copper. The fourth type
contains significantly less lead than the others. These differences are barely visible to the naked
eye, but are partly noticeable under magnification; it further appears as if the dark translucent
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Schwahn
enamel types were not applied continuously over the entire bowl, but were applied in some areas
first and in adjacent areas later (fig. 5). The reason for the use of these different enamel types and
for the appearance of a non-continuous enamel application could not be explained and needs
further research; task sharing within the workshop or a late change to the final design of the bowl
might be possible explanations. Additionally, it was found that the use of infrared reflectography
(IRR) in the region of 950–1150 nm helped to differentiate visually between some of the
different compositions of the dark translucent enamels.
Fig. 5. Detail of an area on the inside of the bowl near the coat of arms (see fig. 2 for overall) of
two dark translucent enamel types with different chemical compositions, separated by a
light line suggesting a non-continuous enamel application.
Although the shape of most footed enamel bowls are deeper and the undersides richly
decorated with grisaille painting, a similar shallow bowl from the same workshop area and
period with an undecorated underside exists at the HAUM (Müsch 2002, 265; inv. Lim 83). This
piece, however, is not footed but fabricated as a bowl and rests directly on its bottom. Several
factors, for example the scratches and abrasions found on the Cologne bowl’s underside, suggest
that it too may have originally been made without a foot.
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THE FOOT
The underside of the foot is signed in gold “I Laudin Emaillieur à Limoges”. However, the
signature is hardly visible in reflected light because the gold particles are sparse and have sunk
deeply into the enamel below. Heavy scratches on the enamel, which are located almost
exclusively over the signature, appear as if they were added intentionally to make the surface
look old and worn. Similar to the signature, the golden monogram on the foot’s right side is also
barely visible in reflected light. Strangely, the monogram letters “RC” do not correspond to the
initials of the original owner of the bowl—and no other family member in the seventeenth or
eighteenth century was identified whose initials would fit the monogram. Contrary to the bowl,
no initial ground layer of clear enamel was applied underneath the colored enamel. The dark
translucent enamel of the foot is redder in color than that of the bowl. Although at first glance the
enamel of the foot appears to be in a better condition than the enamel of the bowl since the latter
is heavily scratched, the foot enamel shows a dull, milky haze in raking light due to an advanced
degree of glass corrosion. µ-XRF revealed a similar lead content but a lower iron content, a
much lower copper content, and a higher potassium content compared to the bowl. Examination
with IRR further gave a hint of the homogeneity of the object’s dark translucent enamels: Unlike
the underside of the bowl, the enamel of the foot appeared almost perfectly homogenous.
Horizontal, parallel grooves were observed on the foot’s copper base indicating that a spinning
lathe was used for shaping—a process rather typical of nineteenth-century enamel production
(Speel 1998, 33), while the common copper shaping method for painted enamels of the sixteenth
and seventeenth century was raising, and no such grooves were present on the bowl’s copper
base. The squat shape of the foot is rather unusual, as is the lack of any grisaille decoration on
top of the dark enamel.
THE COVER PLATE
Sixteenth- and seventeenth-century enamellers often attached circular cover plates within feet in
order to hide the mechanical assembly. As with bowls and feet, cover plates may also be
replaced with ones from other original sixteenth- and seventeenth-century objects or be produced
only for the purpose of restoration in the nineteenth century. µ-XRF of the cover plate’s enamel
composition could not be carried out as the plate was not accessible to the instrument. However,
the use of IRR again brought unexpected results by penetrating the dark translucent enamel and
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Schwahn
revealing a rectangular structure in the center of the copper base (fig. 6). The additional use of Xray computed tomography (CT) revealed that this structure is actually a strip of sheet metal that
is stitched through two slits cut into the copper base; CT further showed that both ends of the
strip are formed into hooks on the other side of the cover plate (fig. 7).
Fig. 6. Infrared reflectography image of cover plate on underside of footed bowl (fig.1) in the
region of 950–1150 nm.
Fig. 7. X-ray computed tomography image of longitudinal section through the foot and the
cover plate of the footed bowl (fig. 1).
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Structures like this have been observed on cover plates of other Limoges enameled footed bowls
and tend to be original sixteenth- and seventeenth-century fabrications, although studies about
their exact use or application have apparently not been published yet. In the course of the former
nineteenth-century restoration of the Cologne footed bowl, the cover plate was fixed to the foot’s
inside by filling the void between plate and bowl with a filler material; thus the sheet metal
hooks do not fulfill any direct assembly or mechanical function now.
CONCLUSION
In conclusion, this detailed study suggests that the object is a pastiche. The bowl is likely an
original Laudin enamel of the seventeenth century that was possibly fabricated without any foot
at all. The foot may instead have been fabricated and added in the nineteenth century. In turn, the
cover plate inside the foot is probably sixteenth- or seventeenth-century origin. The multidisciplinary investigation provided new insight into and a better understanding of the object and
its history, and will hopefully lead to additional research. In particular the use of IRR, apparently
not commonly used for the investigation of painted enamels up to now, which provided
interesting observations on the composition and homogeneity of the enamel and on the
construction of the copper support. The potential of this examination deserves further
exploration. With the identification of a lead white-based primer layer as part of the former
restoration, a parallel could be drawn to a similarly restored object in another collection with
known information about the date and executor of the restoration. Future detailed observations
and documentation of former restoration techniques as well as the identification of the materials
used might allow assignment of treatments to specific restorers or workshops.
REFERENCES
Beillard, B. 2002. Le regard du restaurateur. In La rencontre des héros, ed. V. Notin. Limoges:
Musée Municipal de l’Évêché. 18–20.
Beillard, B. 2007. Les émaux peints. In Conservation, restauration du verre. Actualité et
problématiques muséales. Actes du colloque, atelier musée du verre, ed. Écomusée de
l'Avesnois. Trélon. 54–58.
Biron, I. 2002. Le regard du physicien. In La rencontre des héros, ed. V. Notin. Limoges: Musée
Municipal de l’Évêché. 22–33.
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Schwahn
Brill, F. 1964. Sammlung Lückger. Köln: Museen der Stadt Köln.
Bronk, H. and S. Röhrs. 2002. Die Materialzusammensetzung der Glasflüsse im Limousiner
Maleremail. In Maleremails des 16. und 17. Jahrhunderts aus Limoges, ed. I. Müsch.
Braunschweig: Herzog Anton Ulrich-Museum. 38–49.
Caroselli, S. L. 1993. The painted enamels of Limoges. A catalogue of the collection of the Los
Angeles County Museum of Art. Los Angeles: Los Angeles County Museum of Art.
Farnsworth, J. R. 1977. Anwendung von Metallbildträgern in der europäischen Malerei,
unpublished thesis. Staatliche Akademie der Bildenden Künste Stuttgart.
Gettens, R. J., H. Kühn, and W. T. Chase. 1993. Lead White. In Artist’s pigments – A handbook
of their history and characteristics, ed. R. Ashok. New York: Oxford University Press. 2:67–81.
Müsch, I. 2002. Maleremails des 16. und 17. Jahrhunderts aus Limoges. Braunschweig: Herzog
Anton Ulrich-Museum.
Netzer, S. 1999. Maleremails aus Limoges. Der Bestand des Berliner Kunstgewerbemuseums.
Berlin: Staatliche Museen zu Berlin – Preußischer Kulturbesitz.
Speel, E. 1998. Dictionary of enamelling. Aldershot: Ashgate.
Speel, E. 2008. Limousiner Maleremail. Die Werkmaterialien und ihre Anwendungstechniken
als bestimmende Faktoren für die stilistischen Entwicklungen. In Maleremail aus Limoges im
Grünen Gewölbe, ed. Ulrike Weinhold. Dresden: Staatliche Kunstsammlungen Dresden. 150–
157.
Thiou, E. 2002. Dictionnaire biographique et généalogique des Chevaliers de Malte de la
Langue d’Auvergne sous l’Ancien Régime (1665-1790). Versailles: Mémoire & Documents.
Thomas, B. 1960. Die Münchner Harnischvorzeichnungen des Étienne Delaune für die Emblemund die Schlangengarnitur Heinrichs II. von Frankreich. Jahrbuch der kunsthistorischen
Sammlungen in Wien 56: 7–62.
Verdier, Ph. 1995. Limoges enamels. In The Taft Museum – Its history and collections. New
York: Hudson Hills Press. 328–405.
Wehlte, K. 1992. Werkstoffe und Techniken der Malerei. Ravensburg: Otto Maier, 6.
ACKNOWLEDGMENTS
This investigation was carried out in the scope of a thesis project at the Staatliche Akademie der
Bildenden Künste in Stuttgart, Germany, in cooperation with the Museum für Angewandte Kunst
in Cologne. I would like to thank all the many conservators, scientists, and curators who
contributed to this work. Further special thanks for the scientific analyses are due to: Dipl.-Ing.
Tobias Rapp, Carl Zeiss 3D Metrology Services Aalen, for CT; Prof. Dr. Ch. Krekel, Dr. A.
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Schönemann, and Dipl.-Rest. A. Fischer, Staatliche Akademie der Bildenden Künste Stuttgart,
for IRR, FTIR, and SEM-EDX respectively; Dr. M. Griesser and Dr. V. Pitthard,
Kunsthistorisches Museum Wien, for GC-MS; and Dr. S. Röhrs, Rathgen-Forschungslabor
Berlin, for µ-RFA.
AUTHOR
BIRGIT SCHWAHN, Diplom-Restauratorin Germany
[email protected]
Ms. Schwahn entered the conservation study program for archaeological, ethnographic, and
decorative arts objects at the Staatliche Akademie der Bildenden Künste in Stuttgart, Germany,
in 2004. During her studies, she interned and collaborated with major German as well as foreign
museums and institutions including the Museum für Angewandte Kunst in Cologne, the Musée
d’art et d’histoire in Geneva, and the National Museums Scotland in Edinburgh. She graduated
from Stuttgart in 2009 and recently completed a graduate internship at the J. Paul Getty Museum
in Los Angeles researching Limoges enamels.
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AN EXAMINATION OF A FOURTEENTH-CENTURY BASSE-TAILLE
ENAMEL DIPTYCH FROM COLOGNE: IS IT FOURTEENTH CENTURY AND IS IT
FROM COLOGNE?
DIANA JOHNSON GALANTE
ABSTRACT – The subject of this study is a miniature enameled Diptych with scenes of the
Annunciation, Nativity, Crucifixion, and Resurrection, a gem-like object for personal devotion,
currently in The Cloisters, the medieval branch of the Metropolitan Museum of Art in New
York. The enamel was examined using microscopy, radiography, and scanning electron
microscopy coupled with energy dispersive X-ray spectroscopy to investigate whether it was
made in Cologne, and if its attributed date of manufacture of 1300–1325 is correct.
INTRODUCTION
The hinged diptych is decorated on the exterior and interior with four narrative scenes, produced
using the basse-taille enameling technique on both sides of the two panels, and set within a
silver-gilt frame (fig. 1). The exterior panels with scenes of the Resurrection and Crucifixion are
composed of enameled color fields and gilt reserve with engraved details. The color palette
includes translucent bright blue, green, purple, yellow-brown, blue-grey, very dark blue-black,
and opaque red enamels. The interior panels have narrative scenes of the Annunciation and
Nativity and cast architectural elements in the form of three-dimensional gilt appliqués
positioned above the enamel and held by tabs into the frame. The backgrounds consist of
translucent bright blue, green, purple, and reddish-yellow enamels without metal in reserve. The
panels are bezel-set into the gilt frame, possibly a replacement, with a five-knuckle hinge. Due to
its size, only about 6 cm tall by 4.4 cm wide when closed, it was easily portable and required the
close inspection of the beholder. The size of the piece limited the scope of the compositions, but
the craftsmen managed to endow the object with detail, emotion, and beauty.
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Johnson Galante
An Examination of a Fourteenth-Century Basse-Taille Enamel Diptych from Cologne
Fig. 1. Diptych with scenes of the Annunciation, Nativity, Crucifixion, and Resurrection, 1300–
1325, approximately 6 x 8.8 cm (open), The Metropolitan Museum of Art, acc. no.
1980.366. Exterior (top) and interior (bottom) views. Photograph © The Metropolitan
Museum of Art.
Scholars have debated the location of where the diptych was produced, and conjectures
have included Paris, Vienna, England, and finally the Lower Rhine, probably Cologne. The aim
of this investigation is to explore The Cloisters’ diptych through historical research, comparisons
to other artworks, and scientific analysis to determine the plausibility of its attribution. Each
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panel has fourteenth-century comparisons to portable manuscript illumination, paintings, ivories,
metalwork, and other enamels from Northern Europe, as well as objects present in Cologne in
the beginning of the fourteenth-century. The possibility of a nineteenth- or twentieth-century
fabrication will be discussed, as well.
HISTORY AND CONDITION
Located on the Lower Rhine, Cologne was a center for commerce and pilgrimage, and had
connections in business as well as the arts with Paris, Prague, and other cities in Northern
Europe, from which artistic style derived. Cologne had a long-standing metalworking tradition
that continued from the Roman period into and beyond the Gothic, and it held the status of a
leading metalworking center in Europe in the Middle Ages (Chapuis 2003). Like other wellknown enameling centers in Limoges and the Meuse Valley, Cologne’s artisans also produced
enameled objects, including the monstrance-reliquary of circa 1300 for Graf von Isenburg,
perhaps the earliest-known example of German translucent enameling (Campbell 1983). Based
on this date, the diptych could have been produced as early as the first quarter of the fourteenth
century in Cologne.
The diptych is in very good condition, with only minor damage to the enamel of one
interior panel. Although it has been suggested by an art historian with expertise in enamels that
the enamel on the interior is a nineteenth-century restoration, the colors appear consistent with
those on the exterior of the piece. Furthermore, the colors appear consistent with other
fourteenth-century basse-taille enamels.
ANALYSIS
The diptych was examined carefully using an optical microscope, with additional information
about its manufacture determined by radiography carried out some time after its acquisition in
1980. Analysis of the chemical composition was performed using scanning electron microscopy
coupled with energy dispersive X-ray spectroscopy (SEM-EDS). The work was carried out by
Mark Wypyski in the Metropolitan Museum of Art’s Objects Conservation Analytical
Laboratory in 2008. The SEM-EDS analysis was performed on the object’s surface, including
the colors blue, green, purple, and red. The overall compositions of the enamels were found to be
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Johnson Galante
An Examination of a Fourteenth-Century Basse-Taille Enamel Diptych from Cologne
mixed-alkali: high-potassium (potash) compositions with relatively small amounts of sodium
(soda), magnesium (magnesia), aluminum (alumina), and calcium (lime) were identified.
In general, basse-taille enamel compositions from the fourteenth century have
exceptionally high mixed alkali contents, perhaps over 20% by weight, with a greater percentage
of potassium than soda, and low lime contents (Bowman and Freestone 1997). The percentages
of alkalis on the sample surfaces were determined by SEM-EDS to be approximately 12%, and
the intensity of the potassium peaks indicate that potash would have dominated over the quantity
of soda present, however, weathering, or corrosion, of the glass due to cleaning could have
caused alkalis to leach out over time (Mass 1999). Their original compositions could have had
different proportions, although the general compositions still appear consistent with fourteenthcentury enamels. The glass networks of nineteenth-century enamels have been found to contain
large quantities of lead, often 20–50% by weight. Nineteenth-century glasses in general are
higher in sodium oxide as compared to potassium oxide (Wypyski 2007). Lead was not present
in quantities nearly as high as nineteenth-century enamel glass. Furthermore, a nineteenthcentury replacement likely would be sodium-rich rather than potassium-rich. The overall
compositions, colorants, and associated elements detected within the enamels appear to be
consistent with fourteenth-century European enamel technology, rather than nineteenth-century
enamel manufacture. This data supports the authenticity of the enamels and the object to the
fourteenth century, rather than a nineteenth-century forgery. Furthermore, both the brilliant blue
from the interior and the exterior were analyzed, and found to be nearly identical, and likely both
of fourteenth-century manufacture.
CONCLUSION
The diptych, for such a small object, presents numerous challenges in terms of its attribution to
early fourteenth-century Cologne. In comparison to other enamels of similar size, this diptych is
particularly well-crafted and refined. One must appreciate the ability of the artist to manipulate
his materials so that variations in depth of mere fractions of a millimeter create the illusion of
volume and perception of fine details. The colors complement each other well; the small space
available is used effectively to convey narrative and expression with relative clarity; and, not
only are the general attributes of each scene depicted, but each panel also has details that elevate
the quality and delight the beholder. The specifics behind the object’s commission and
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construction remain mysterious; and yet, regardless of its geographic origin, the diptych as a
whole is a truly magnificent example of medieval art.
REFERENCES
Chapuis, J. 2003. Stefan Lochner: Image Making in the Fifteenth-Century. Turnhout: Brepols.
220.
Campbell, M. 1983. An Introduction to Medieval Enamels. London: Her Majesty’s Stationery
Office:38.
Bowman, S. and I. Freestone. 1997. Early 14th C. Enamelwork: a technical examination of the
hanap cover of All Souls College, Oxford. Techne 6:44.
Mass, J. L. 1999. Instrumental methods of analysis applied to the conservation of ancient and
historic glass. In Conservation of Glass and Ceramics: Research, Practice and Training, ed. N.
H. Tennent. London: James and James:15–28.
Wypyski, M. 2007. Chemical Analyses of Renaissance Enamelled Jewellery. In Glass and
Ceramics Conservation 2007, ed. Lisa Pilosi. Nova Gorica, Slovenia: Grafika Soca:47–59.
AUTHOR
DIANA JOHNSON GALANTE, Conservator in Private Practice
New York, NY 10128, cell (917) 439-6914, [email protected]
Ms. Johnson Galante is a recent graduate of the Conservation Center, Institute of Fine Arts, New
York University, with a Master’s degree in Art History and Conservation. She has practiced
metalworking and enameling for several years. During her graduate studies, she focused on the
study and conservation of enamels. Currently, she is an objects and furniture conservator for a
private practice in New York City.
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JEWELRY OR SCULPTURE? THE LIMOGES MEDIEVAL VIRGINS MADE OF
COPPER AND ENAMEL
VÉRONIQUE NOTIN
ABSTRACT – The Musée des Beaux-Arts, Limoges holds in trust since 1995 the famous
medieval Virgin of Breuilaufa. Following a study on the Limoges coppersmiths, the museum
acquired in 1996 another statuette of the enthroned Virgin (without Child), entirely made of gilt
copper. This paper presents the results of the technical investigation of these two sculptures and
provides a basis for the addition of three recently discovered statuettes of the Virgin (Fournol,
Pavie, and Cahors) to the corpus of fifty-three published works by Marie-Madeleine Gauthier in
1993.
INTRODUCTION
The statuettes of the Virgin and Child made during the end of the twelfth century and the middle
of the fourteenth century form an original group in the important production of Limoges
enamels. However, in spite of their similar appearance, they form two distinct categories related
to the different methods of fabrication used and the individual artistic intentions they reveal.
Group 1
The first group belongs to a strong tradition established after 1000 AD in the goldsmith’s
craft in the South of France, which embellishes wood sculptures using precious metals adorned
with cabochons. The Majesty of Saint Foy of Conques (ca. 1000 AD, 85 cm, Aveyron), covered
in gold, is the most famous and ancient example preserved in this tradition. The Virgin of
Orcival (ca. 1170, 65 cm, Puy-de-Dôme) and the Virgin and Child of Beaulieu-sur-Dordogne
(last quarter 12th c., 61 cm, Corrèze) are variations of the same seated figure, but are covered in
silver and are dated two centuries later at the end of the twelfth century.
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Notin
The metalsmiths from Limoges, however, used copper instead of more precious metals
and appropriated this model of enrichment using enamels arranged in the most apt locations,
particularly on the faces of the throne whose flatness naturally lent itself to this type of
decoration. A Virgin with Child can be seen at The Metropolitan Museum of Art in New York
(ca. 1200, 36 cm, inv. 17.190.125), covered with fifty-nine thin pieces of copper, nailed on a
wood core, and assembled together to form a puzzle. Cabochons with colored stones are
arranged on the crowns of the Virgin and Child as well as on the decorative bands that adorn the
garments; beads of dark blue enamel give luster to the figures’ eyes and small turquoise beaded
enamel punctuate the sleeves of the Child. Color predominates on the front of the statuette’s
throne which is completely enameled with foliated scrolls. There are also two medallions, shaped
like diamonds, that are enameled with an ornamental flower pattern and nailed to the sides of the
throne in a very similar way as the reliquary of Ambazac (ca. 1180–1190, 58.6 x 79 x 26.2 cm,
Haute-Vienne)—a masterpiece of the Limoges enamel work that is slightly contemporary.
Fig. 1. Virgin of Breuilaufa, ca. mid 13th c., 47 cm, Haute-Vienne and held in trust at the Musée
des Beaux-Arts, Limoges. Photography F. Magnoux © City of Limoges.
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In the case of the Virgin of Breuilaufa (Haute-Vienne) (fig. 1), it is similar in many respects to
the statuettes just described, except the enamel is strangely concentrated in the figures’ eyes.
This unique feature supports the attribution of this work to the maker of the recumbent figures of
Saint Louis’ children (see Boyer and Notin 2002a-c) and to date it from the middle of the
thirteenth century.
Second Group
The second group of Virgin and Child statuettes derives from internal developments in
the techniques used by the enamellers. In fact, since the end of the twelfth century enamellers
have increased the alternatives between the support of the gilt copper and the enameled colored
decoration, to optimize the effects of light and facilitate an understanding of the iconography
through a hierarchical organization of the decoration.
On a shrine for example, the principal face shows most often religious scenes, while the
reverse is decorated with an ornamental pattern. Very early on, half-relief appliqués were applied
to the main characters on the front to distinguish them from secondary figures. Around 1190, a
blue enameled background in reserve became widespread and the figures may be entirely
appliquéd. These have the advantage of being manufactured separately, in multiples, and then
attached onto supports of various shapes. The figures of the Crucifixion, Christ in Majesty, or the
Enthroned Virgin are of course those which get more elaborate treatment. The figure of the
Virgin—as the one of Christ on the Cross—often matches with Christ in Majesty. This is the
case for the shrine of Saint-Marcel (ca. 1210, 42.4 x 43.3 x 17.3 cm, Indre), adorned with gilt
copper figures which are applied to enameled quatrefoil plaques with rinceaux decoration and
attached to sheets of gilt copper. The shrine of Saint-Viance (second quarter of the 13th c., 65 x
85 x 25 cm, Corrèze) depicts the Virgin and Child surrounded by the apostles: the figure of the
Virgin in gilt copper is attached to an almond-shaped enameled plaque and surrounded by a
frame enameled on the relief. Having larger dimensions than the one on the shrine of SaintMarcel, the Virgin of the Saint-Viance shrine (fig. 2) is also worked in high relief, almost in
ronde-bosse. This Virgin is clearly Gothic in style. The figure of the Virgin, the Child, and the
throne are made of the same thick piece of metal, which is repousséd and chiseled and cut along
a line that defines the front half of the group. The Virgin’s crown is the only added element. The
same manufacturing principle has been used for the even larger appliqué figure of the Virgin in
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Notin
the Musée des Beaux-Arts, Dijon (mid 13th c., 30 cm, inv. D 1086). At this time it is not known
if this medallion belonged to the central part of a shrine or to the front of an altar.
After this technique was completely mastered, the goldsmiths from Limoges started the
production of relief sculptures in the middle of the thirteenth century.
Fig. 2. Chasse of Saint-Viance, second quarter of the 13th c., Corrèze. Detail of the central
medallion. Photography F. Magnoux © City of Limoges.
They simply changed the attachment for the back and the throne on the half-figure of the Virgin
and Child, which were previously secured onto a flat plane, and mounted the sculpture on a
pedestal. This construction appears on the enthroned Virgin (without Child) in the Musée des
Beaux-Arts, Limoges (ca. 1300, 34 cm, inv. 96.547) (fig. 3). The assemblage is simple and made
to provide the best stability. In this way, the back of the Virgin is cut at the bottom level and
extended by a metal strip which is inserted into a slit opened in the seat of the throne. This is
manufactured separately, with four vertical plates—three of them taller than the front plate—
often enameled and cut on the upper strip with a decorative line of keyholes or scallops. The
92
back of the throne has a door and the front part is decorated only on the sides not hidden by the
Virgin’s dress and coat. A fifth horizontal plate is attached at the top: it strengthens the whole
and acts as the Virgin’s seat.
Fig. 3. Enthroned Virgin (without Child), ca. 1300, Musée des Beaux-Arts, Limoges, inv. 96.547.
Detail of the Virgin’s head. Photography F. Magnoux © City of Limoges.
The throne and the figure are generally placed on a small pedestal that is either sloped or has four
feet. The pedestal is often enameled and has a slit in the front for inserting a metal strip attached
to the front part of the Virgin. This allows adjustment of the sculpture on its stand, providing a
similar function as the one applied on the back. The two parts of the Virgin figure are soldered
together. Thanks to the recent discovery of the Virgin of Fournol (ca. 1300, 35.5 cm, Corrèze
(see Boyer and Notin 2002b)) who lost her throne, it was possible to see the internal structure of
this type of statuette and to discover an additional system for attaching the two sections. This one
is indeed reinforced with metal strips alternatively fixed on each part of the sculpture, riveted on
one side and soldered on the other (fig. 4). Metal angle braces secure the two parts of the body
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Notin
together and strengthen the join. The crown is a hoop and disguises the soldering on the Virgin’s
head.
Fig. 4. Virgin of Fournol, Corrèze. Detail of the internal mechanical join. Photography V. Notin
© City of Limoges.
CONCLUSION
With these few examples it clearly appears that Limoges enamellers achieved, with different
techniques, their goal of finding a third dimension and developing the new canons of Gothic art
after perfectly assimilating the Romanesque tradition. But it also appears that during this course
they deviated from the essence of their work: the enamel, a part of the goldsmith art, was
progressively displaced to the background and served solely as an optional complement to the art
of sculpture. This mortal contradiction is unquestionably one of the causes, among others, of the
decline of the Limoges enamels from the first half of the thirteenth century on. Despite this, the
Virgin and Child sculptures are testimony of renovated expression of form and technique and
show the tremendous vitality of the medieval enamels of Limoges.
REFERENCES
Boyer, J. F. and V. Notin. 2002a. L’église hospitalière de Breuilaufa et l’ Image de Notre-Dame
en bosse de bronze doré, fort biau. Bulletin de la Société archéologique et historique du
Limousin t. CXXX:55–90.
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Boyer, J. F. and V. Notin. 2002b. Majesté de la Vierge en cuivre, œuvre limousine, vers 1300:
Notre-Dame de Fournol (c. de Saint-Merd-les Oussines, Corrèze). Bulletin de la Société
archéologique et historique du Limousin, P.V. des séances, 24.09.2002 t. CXXXI:397–399.
Boyer, J. F. and V. Notin. 2002c. Contribution à l’étude du mobilier médiéval des églises ayant
dépendu de l’ordre des Hospitaliers sur la Montagne limousine. Les ordres religieux au Moyen
Âge en Limousin. Les Monédiaires. 195–229.
Boyer, J. F. and V. Notin. 2008. Une statuette de l’Œuvre de Limoges identifiée dans le Gers.
Bulletin de la Société archéologique et historique du Limousin t. CXXXVI:77–81.
Gauthier, M. M. 1970. Les Majestés de la Vierge “limousines” et méridionales du XIIIe siècle au
Metropolitan Museum of Art de New York. Bulletin de la Société des Antiquaires de France.
66–95.
Gauthier, M. M. 1993. Images de la Mère de Dieu dans la décoration de l’autel. Le décor des
églises en France méridionale (XIIIe-mi XVe s.), Cahiers de Fanjeaux 28:87–137.
Gauthier, M. M. 1993. L’Ymage de la mère de Dieu sise à la Sauvetat: statue de l’Œuvre de
Limoges offerte en 1319 par Odon de Montaigu à la Commanderie de Saint-Jean de Jérusalem
au diocèse de Clermont. Bulletin de la Société archéologique et historique du Limousin t.
CXXI:121–136.
Hildburgh, W. L. 1955. Medieval copper champlevé enamelled images of the Virgin and Child.
Oxford.
AUTHOR
VÉRONIQUE NOTIN, Curator in Chief and Director
Musée des Beaux-Arts de Limoges - Palais de l'Evêché, 1 Place de l'Evêché F, 87000, Limoges,
France, tel. 33 (0)5 55 45 98 10, fax 33 (0)5 55 34 44 14, [email protected]
Ms. Notin has been Curator in Chief and Director of the Musée des Beaux-Arts de Limoges
since 1988. She is a member of the French Enamel Group and has been in charge of several
exhibitions focused on Limoges medieval and Renaissance enamels. She also organized the
international symposium, “Limoges Painted Enamels: The Heart of the Decorative Arts of the
Renaissance” in 2004. After four years of work, which allowed the complete reorganization of
the museum, the institution will reopen its doors on December 4th, 2010 with a department solely
dedicated to the enamel collection.
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CONCERNING A MYSTERIOUS LIMOGES ENAMEL GROUP OF THE PASSION
AFTER DÜRER
ISABELLE BIRON AND MONIQUE BLANC
ABSTRACT – In 2002, five polychrome enamel plaques, The Good Shepherd, The Pietà, The
Entombment, Christ Crowned with Thorns, and Christ before Caiaphas, were considered
questionable by Limoges enamel specialists during a meeting at the Musée des Art Décoratif,
Paris. The following lecture will discuss the analysis of these enamels and compare them to
similar objects in other collections.
INTRODUCTION
After a meeting in 2002 of the “enamel group” at the Musée des Art Décoratif in Paris, a trip to
England with the same group allowed an opportunity to examine the enamels stored at The
British Museum, the Victoria and Albert Museum, and the Wallace Collection in London, as
well as the Ashmolean Museum in Oxford. During these three days, surrounded by the
magnificent collections of these museums, they were able to study a rare “anonymous”
altarpiece in the Wallace Collection made of 24 polychrome enamel plaques depicting the
Passion of Christ after Albrecht Dürer’s, Small Passion, 1509–1511, which consisted of 37
woodcuts in the series (one set located in Germanisches Nationalmuseum, Nuremburg and the
other at the Petit Palais, Musée des Beaux-Arts de la Ville de Paris). The following year,
Suzanne Higott, Curator of earthenware, Limoges enamels, and glass at the Wallace Collection,
in preparation for the catalogue raisonné of the painted enamels and glass, sent four of these
plaques to the Centre de Recherche et de Restauration des Musées de France (C2RMF). These
plaques were stylistically very similar to three of the plaques of the Passion exhibited in the
collection of the Musée des Art Décoratif—all following the model of the Small Passion by
Dürer (figs. 1, 2).
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Biron and Blanc
Concerning a Mysterious Limoges Enamel Group of the Passion of Dürer
Fig. 1. Plaque, Christ Crowned with Thorns, Master of the Passion after Dürer, ca. 1560–1570 or
last quarter of 16th c., Limoges, approximately 10 x 8 cm, Musée des Art Décoratif, Paris,
inv. Gr 6.
Fig. 2. Plaque, The Mocking of Christ, ca. 1560–1570 or last quarter of 16th c., Limoges,
approximately 10 x 8 cm, Wallace Collection, London, inv. IIIF250.
98
While the Wallace Collection plaques were considered nineteenth century by a large majority of
experts, Higott requested analysis at the C2RMF laboratory in 2006 to investigate the chemical
composition for the plaques. This analysis confirmed an earlier manufacture date; therefore
additional plaques from several institutions, possibly belonging to the same workshop, were
analyzed at the C2RMF laboratory for comparison.
DISCUSSION
In addition to the Musée des Art Décoratif and the Wallace Collection’s plaques of the Passion,
the following institutions enamels were also investigated: the Museu Nacional Soares dos Reis,
Porto; the Museu Nacional de Arte Antiga, Lisbon; Musée des Beaux-Arts, Lyon; and the Musée
du Louvre, Paris. These institutions were selected because of the notable stylistic similarities in
the enamels. They also had uniform dimensions, approximately 10 x 8 cm, and all belonged to an
altarpiece (fig. 3).
Fig. 3. Plaque, Christ’s Entry into Jerusalem, after the Small Passion woodcut by Dürer, ca.
1560–1570 or last quarter of 16th c., Musée des Beaux-Arts, Lyon, inv. L 467.
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Biron and Blanc
They are unique among the Limoges painted enamel production, because the copper, the
polychrome enamels, and the extensive gilding are generally in good condition; therefore these
plaques were considered either nineteenth-century pastiches or examples of a later production.
Because of their questionable attribution date, they were frequently relegated to storage.
It was therefore essential to confirm the date of production through chemical analysis of
the glass. The C2RMF laboratory has an important analytical and technical database on the
production of painted enamels of Limoges from the fifteenth to the nineteenth century that
allows for determining a chronological evolution of the chemical development of glass
composition of enamels, as well as authenticating their attribution date. The dating method used
is a comparative measure. For one object, the chemical composition of every enamel color is
compared with similar colors on the reference database—made of objects well dated—thus a
date range could be proposed for each object analyzed. The enameled plaques were all analyzed
in the C2RMF laboratory using ion beam analysis in PIXE and PIGME mode with the AGLAE
accelerator (3 MeV proton beam extracted in air; two X ray detectors: one with Helium flux and
one with 50 micrometers aluminum filter; and one gamma ray detector, around 1 nA intensity,
with a 2–3 min. acquisition time).
Fig. 4a. Detail of figure 1, head of Christ.
100
Fig. 4b. Detail of figure 3, head of Christ.
CONCLUSIONS
The laboratory study of the chemical composition of the glass established in every case an early
manufacture, from 1560–1600. The technical examination using microscopy also provided
information on the fabrication methods for these plaques (figs. 4a, 4b). This study allowed
reattribution of a group of painted Limoges enamel plaques to the sixteenth century, which were
considered for the most part modern reproductions. This may also provide evidence for a new
workshop of enamellers of Limoges, active between the middle of the sixteenth century until the
beginning of the seventeenth century, working after Pierre Reymond. This study also helped to
clarify uncertain attributions for common Limoges workshops during the Renaissance: Pierre II
Veyrier, Pierre Vigier dit Callet, Maître Fin, Maître de la Passion, and finally, the earlier works
of Pierre Reymond and his followers.
AUTHORS
ISABELLE BIRON, Senior Research Scientist and Engineer
Laboratoire du Centre de Recherche et de Restauration des Musées de France, Palais du Louvre porte des lions, 14 quai François Mitterrand, 75001, Paris, France, tel. 00 33 1 40 20 58 29,
[email protected]
Ms. Biron’s research focuses on the techniques of manufacture, deterioration, conservation, and
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Biron and Blanc
dating of glass, using ion beam analyses (PIXE, GETS, NRA, and RBS), as well as MEB-EDSX,
XRD, Raman microscopy, and IR. She has studied the deterioration of glass for over fifteen
years, specifically the degradation mechanisms involved in different environmental conditions.
She has presented this work at the Experts’ Meeting on Enamel Conservation in 2008, as well as
at ICOM-CC Glass and Ceramics Group Meeting, and the Association Internationale pour
I'Histoire du Verre. She has published widely on enamels and has worked in collaboration with
many curators and conservators throughout Europe and the United States on the analysis of
enamels.
MONIQUE BLANC, Chief Curator of the Department of Medieval and Renaissance Art
Musée des Art Décoratif,107 rue de Rivoli 75001, Paris, tel. 00 33 1 44 55 58 22,
[email protected]
Ms. Blanc received her doctorate in Art History from the Ecole du Louvre, after studying at the
Sorbonne. Her main area of research was developing the connections between Eastern and
Western Coptic Art from the fourth century. She is the author of several books, among them the
collection catalogues for the Musée des Art Décoratifs on medieval and Renaissance altarpieces.
She has also curated several exhibitions and published numerous articles including collaborative
scientific investigations in art.
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