Lacquer can be a very forgiving finish material, and if you understand its characteristics, repairing damage to a lacquered surface can be easy. Lacquer is basically cellulose dissolved in a solvent. A lacquer surface coating hardens when the solvent evaporates, and applying more solvent will soften it again. This simple fact enables you to use strategies that would be impossible with a cured finish like polyurethane or varnish. Not many lacquer repair techniques involve sanding, and those that do usually also involve spraying more material. Only one extreme defect calls for stripping the wood and spraying a new finish.
Spray a wet coat of pure lacquer thinner on a surface that has cracks, orange peel or roughness. The thinner will emulsify the surface and the defects should disappear when it hardens again. You can get the same results by spraying a full wet coat of thinned-down lacquer.
Add a retarding agent to the thinner to correct blushing, a condition whereby trapped moisture causes the lacquer to turn cloudy. The retardant slows the evaporation of the thinner, giving the moisture time to escape before the surface hardens.
Bleed the air lines of the spray gun and wipe moisture from the tip if the finish surface develops pin holes. They are caused by water and should disappear after recoating with moisture-free material.
Turn down the pressure of the spray gun and cool down the surface or move it into the shade if the finish develops bubbles. They can be caused by heat or by excessive spray pressure. If turning down the pressure doesn't help and you can't reduce the ambient temperature, wait for a cooler day to recoat.
Sand sags and runs with 220-grit wet/dry sandpaper lubricated with a little water after the finish has hardened. Wipe the surface with a rag and recoat it with lacquer, thinning the material as little as possible. Sags are usually the result of spraying with lacquer that is too thin, but they may also be the result of spraying a coat that is too thick. Spray less material when you recoat.
Strip the finish if it develops craters or it separates. This defect is the result of silicone in the wood. Wipe the wood down with lacquer thinner or naptha before you spray it again. Add a flowing agent to the lacquer to help it level out.
Tips & Warnings
- Cratering is one of the most serious defects, and you may not be able to prevent it if you can't remove all the silicone from the wood. You may be able to minimize it, however, by spraying several thin coats of lacquer, sanding each coat flat before applying the next one.
- Because lacquer redissolves, you can repair small cracks and holes in a lacquer finish by brushing on fresh lacquer with a small paintbrush.
- Wear a respirator when spraying lacquer or lacquer thinner and keep the room well ventilated. Both products are flammable, so keep them away from open heat sources.
Things You'll Need:
- Spray gun
- Lacquer thinner
- Retarding agent
- 220-grit wet/dry sandpaper
- Flowing agent
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