Finishing Woodturnings with Lacquer

“Finishing Woodturnings with Lacquer”
© Stephen Hatcher 2011
[email protected]
www.stephenhatcher.com
Step 1 - Sanding Bare Wood I leave the foot unfinished and only complete steps 1-6 on the
front face. It’s easier to hold the platter in the lathe chuck while sanding everything except
the foot.
Step 2 - Seal Surface Pores and Add Background Color Heat the work to about 120F.
Using Z-Poxy, fill all the pores and pits. Spread as thin as possible and allow to cool then cure.
Sand using 400 grit. This sanding can sometimes be done wet to reduce further pitting of the
inlay but it’s messy.
If a background color is desired in the piece, either color the wood first before applying the
Z-Poxy or add that color (diluted in denatured alcohol) to the Z-Poxy when first applied. If
the color is applied before the Z-Poxy, add a little dilute shellac to the color plus DNA to get
a uniform color.
Step 3 - Prime with Shellac After sanding the piece with 400 grit only and getting a uniform
surface, spray with dilute shellac to make the surface bond to lacquer as well as possible.
Step 4 - Airbrush Additional Color Accents Add additional color accents as desired using
an airbrush. Dilute the colors with diluted shellac to improve bond. Clean the airbrush
immediately with DNA to prevent clogging.
Step 5 - Apply Sealer Coats of Lacquer (no sanding sealer) Apply several light dusting
coats of lacquer. Do not use a sanding sealer, it’s creates a weak foundation for the lacquer.
Wait several minutes between spraying light coats to allow the lacquer to air dry (it’s not cured
however).
Step 6 - Allow Sealer Coats to Cure
in the curing oven at 120F overnight.
Wait about an hour or more after spraying then place
Step 7 - Build Lacquer Remove the work from the curing oven and allow it to cool for 30
minutes or more. Then spray a coat of lacquer that just wets the surface, not too heavy or runs
will form. Repeat spraying coats every 5 minutes or so but be sure the previous coat is not
sticky (i.e. it has air dried). After 4-5 coats let the work air dry overnight, then cure at 120F
for one day.
Step 8 - Fill Voids Sometimes pits show up in the wood and/or the inlay. Lacquer abhores
pits and pulls away from them due to surface tension. Though additives can be used to reduce
this tendency, I have found them only slightly effective. Instead fill the pits with thickened
lacquer. After 4-5 coats let the work air dry overnight, then cure at 120F for one day.
Step 9 - Remove Orange Peel and Filling Nubs Remove the work from the curing oven
and allow it to cool for 30 minutes or more. Use 400 grit wet/dry sandpaper to remove orange
peel and nubs from filled voids. Be careful not to sand through the lacquer. It’s helpful to use
a sanding block when sanding down nubs.
“Finishing Woodturnings with Lacquer (cont.)”
© Stephen Hatcher 2011
[email protected]
www.stephenhatcher.com
Step 10 - Build Lacquer Spray a coat of lacquer that thoroughly wets the surface, not too
heavy or runs will form. Repeat spraying coats every 5 minutes or so but be sure the previous
coat is not sticky (i.e. it has air dried). After 4-5 coats let the work air dry overnight, then cure
at 120F for one day.
Step 11 - Sand to 4000 Grit Remove the work from the curing oven and allow it to cool for
30 minutes or more. Use 800-1000 grit wet/dry sandpaper to remove any surface irregularities.
Always use dilute soapy water as a lubricant. Don’t power sand. Work carefully so you don’t
sand through the lacquer. When the surface is free of defects use Abralon pads in grits to
thoroughly rub out the surface using 1000, 2000, and 4000 grits. Keep the sanding pads wet
with dilute soapy water.
Step 12 - Buff Only and Bake Buff at low speed (about 1750 rpm with an 8” firm cotton
buffing wheel) using Moser’s Coarse Buffing Compound. Keep the work moving otherwise a
spot can get heated and this will damage the lacquer. Buff just enough to remove the sanding
marks. If there are defects that require sanding then sand those areas and rebuff until satisfied.
Bake 3-4 days at 120F or 14 days at 70F.
Step 13 - Final Buffing and Polishing Buff with white diamond at 1750 rpm using a soft pad
about 8” in diameter. Then buff quickly using a small amount of carnauba wax.
Rules:
• Avoid mixing lacquer brands or lacquer types or glossinesses. Start and finish with the
same lacquer. Always use nitrocellulose lacquer on wood, never use acrylic lacquer.
• Use lacquer, a spray gun, and artwork that is at about 70F.
• Apply many thin layers, not one or two heavy layers. Heavy layers are more likely to
crack.
• Never use an air supply shared with pneumatic tools. Air tool oil can get in the air line and
ruin your finish.
• It’s usually best tse the silicon carbide sandpaper (1000+ grit) that guitar finishers use. The
grit is more uniform resulting in a consistent surface and it’s worth the extra cost. Suppliers
include lmii.com and stewmac.com.
• Always use a slow buffer: about 1750 rpm with an 8” buffing wheel. Higher speeds can
damage the lacquer by allowing it to get hot from friction.
• Always wrap lacquer finished artwork in 6+ layers of artwork tissue before wrapping it in
bubblewrap. Bubblewrap reacts with lacquer and will mar the finish. Always wrap the
bubblewrap so that the bubbles face outward.
“Finishing Woodturnings with Lacquer”
© Stephen Hatcher 2011
[email protected]
Defects in Lacquer
Orange Peel occurs when droplets of sprayed
lacquer “dry” on the surface before fully flowing
out. This is almost unavoidable to some extent.
But it’s much worse if the air temperature is
about 70F, or the gun air pressure is low (poor
atomization), or the lacquer too viscous.
Lacquer will tend to flow much more evenly
on top of another layer of lacquer if that layer
is smooth.
Tiny Bubbles occur when the solvent in the
lacquer comes out of solution too quickly
(it’s too warm) or if the wood is warming up
causing the air in wood pores to push into the
lacquer. Never leave a lacquered piece sitting
in the sunshine in a misguided effort to speed
the ‘drying’ or curing process. You can end up
with bubbles the size of quarters.
Dust and Hair are hard to avoid in a woodshop
or if you have pets. Try to keep the spray area
as clean as you reasonably can but don’t worry
excessively about it. These defects sand out
easily.
Pits occur when the wood itself has pits, as
in burl or open grain woods. Lacquer has a
high surface tension and pulls away from pits
making them even more distracting. Either
fill them before spraying with Z-Poxy, epoxy,
wood filler, or inlay or fill them after spraying
using lacquer stick or thickened lacquer applied
with a dropper.
www.stephenhatcher.com
“Finishing Woodturnings with Lacquer”
© Stephen Hatcher 2011
[email protected]
Defects in Lacquer (cont.)
Telegraphing occurs when variations on the
surface are directly transferred to the lacquer
surface. As wood dries out or inlay thoroughly
cures there may be shrinkage. Not so much
that you can feel it but enough to be obvious on
a glossy surface. This can usually be removed
with 2000 grit wet/dry sandpaper (always sand
wet) followed by buffing and polishing.
Fisheye occurs when oil or silicon get on the
wood or in the spray. It usually gets in the spray
by way of the compressed air hoses if they were
also used for pneumatic tools. If possible use
a separate air line and compressor for spraying
lacquer. Do not spray lubricants in the presence
of your artwork.
Cracking occurs when the lacquer is applied too
heavily. Lacquer is basically a long molecular
chain and in thin layers it lies and creates a
strong film. In thick layers it may not form a
strong film and it will crack as it cures or as the
wood moves. You can’t fix this, you have to
strip it off and redo the application correctly.
Crackle occurs when two different lacquers
react in some bizarre otherworldly way. Never
mix types of lacquer like nitrocellulose (good)
and acrylic (bad). Avoid mixing brands of
lacquer if possible just to be safe. Crackle is a
surface defect that differs from cracking in that
crackle does not go through the lacquer film.
But if you sand it off and rebuff, the defect
reappears. You must strip and reapply.
www.stephenhatcher.com