Question from a Client
I bought this very old Chinese tray with half the lacquer worn off. I want to preserve what is left and use it to work on.
Can I paint or spray some kind of clear finish on it? You are our guru for surfaces on wood. All I know is textiles.
Thanks for your help.
Shellac is your best bet as shellac will stick to almost anything, and almost any finish will bond to shellac.
You can purchase shellac flakes and mix your own 2 lb cut with denatured alcohol but this shellac by Bulls Eye works really well and is very convenient to use. The most important part of application is temperature and humidity conditions. Make sure you work with a scrap piece of wood and do some test samples before applying it to your piece.
The ideal conditions would be a sunny day with temperatures around 75 to 80 degrees. If it is a rainy or overcast day, then do not spray shellac, wait for a dryer day. Shellac can absorb moisture from the air on a day with high humidity levels and the result will be a “milky”color to the finish. If you can spray it indoors in your studio, then make certain that the room/space has a thermometer in it and it reads 75 degrees or warmer for best results.
When I work on a piece that I am restoring, I lightly clean the surface first and try to remove any wax that has been applied over the years. I use to use Naphtha, but it has been removed from California’s hardware and paint stores for health reasons. Old Asian lacquers are Urushi lacquers which are natural resin from the Sumac trees. Shellac is a natural resin harvested from the Lac bugs in India and other Asian countries. Even if you are not able to light clean the surface with a mild solvent, I believe the shellac will still bond to it. Cleaning the surface first is still your best option.
Since Naphtha is no longer available, I would try some mineral spirits instead. Before using the mineral spirits, start by lightly brushing the surface with a soft, dry paint brush to see if the old finish flakes off or is still intact. Once you have lightly brushed the surface and removed any dust or loose material from it, then take an old t-shirt or clean cotton cloth and moisten it with some paint thinner (you can purchase the odorless type which is more user friendly) and gently rub the surface. Do not use any abrasive material like steel wool or scotchbrite, it can remove some of the finish.
Let the surface dry. It might look dull as a result, but it should be cleaner.
Shellac flows best when it is warm. When I spray it from a solution I have mixed or from a can, I always try to warm it first.
Cans are much easier to deal with. On a sunny day, simply leave the can in the sun until the can feels warm to your hands.
I have an oil filled radiator in my finishing room and I place the can on it until it feels really warm or you can just place the can next to a light bulb as a heat source.
Shake the can really well, and use long, light, uniformly even strokes across the surface, overlapping each stroke. The goal is to apply a light, wet, uniformly thin coat over the entire surface. The surface should look glossy without any dry spots but do not apply too much at a time to the point where it puddles or runs.
The great thing about shellac is that in addition to protecting the surface, it also acts like a coat of glue bonding everything together.
You might want to apply several coats depending upon how it looks. Apply a second coat of shellac before doing any sanding so as not to damage the original finish. After the second coat has dried, then lightly sand it with some 600 grit sand paper to smooth and blend the old and new surfaces. Try not to cut through the shellac into the original finish, but if you do, just apply another coat of shellac. After the last coat of shellac has dried overnight, you could lightly rub it with 0000 steel wool to further smooth and blend everything. I like to follow up with a light coat of Renaissance wax to bring up the soft sheen after it has been dulled by the steel wool.
Please remember to practice on test pieces first before working on your prized possession.