Sanding Dust Trapped Under Post-Catalyzed Lacquer
A finishing mistake left white dust trapped under the finish. Now, stripping and refinishing is the only fix. October 8, 2005
Recently we sprayed a Wenge table with a post cat lacquer from Industrial Finishing Products. We proceeded to rub it out, but wet sanded (with water) through the finish on one edge by accident, making one more coat inevitable. Thinking we had cleaned out all of the sanded finish from the pores with naphtha, we top coated. We found that some of the residual white dust was now trapped under the top coat. Were we crazy to think it would re-dissolve? Or does wet sanding with water have to be cleaned with water? Now some of the table’s pores are white and will not fly. Can anybody advise us on the problem and help us decide on a stripper should we need to refinish?
From contributor D:
If your lacquer is a solvent base the additional coat should have "melted" with the previous coat. If you have white spots, it sounds to me like blushing has occurred because you trapped moisture in between your coats. Wiping with naphtha after sanding will remove all the dust with no problem.
From contributor B:
I would never assume the white dust in the pores would re-dissolve. Now you have to get the material off and still deal with the pores underneath, which may be more difficult as they have become partially dissolved. Also, the dust in the pores could cause adhesion problems. I would use appropriate thinner and wipe the top clean and start over. This will also pull out and guarantee the cure of the white dust.
From Paul Snyder, forum technical advisor
Catalyzed finishes are cross-linking finishes and don't have the burn-in that evaporative finishes (NC lacquer, shellac) have. With crud trapped in the pores, under a coat of finish, refinishing is your only option. Related Web Page: Stripping
Use any paint & varnish remover. Your finish supplier probably has a selection to choose from. Stripper with methylene chloride (MC) works the fastest.
Usually, before you rub out a finish you want a level film, not dimples from the pores. Otherwise, you end up with compound and sludge in the dimples.
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