Little Bubbles or Bumps in Finish

Little Bubbles or Bumps in Finish

I recently built a fireplace mantle out of red oak boards and plywood that matched my cabinets and decided to use the same lacquer finish that was used on the cabinets. I used all of the same Kelly-Moore products that were used on my cabinets. I used an oil based stain, sanding-sealer, and a high gloss lacquer. I used (for the first time) an HVLP rig that I borrowed from a friend. The spraying was done in the garage and I used two portable space heaters to warm-up the area and then turn them off, apply the finish, open up the garage to air it out, and then do it again. I did light sanding and wiped it off with a tack cloth in between applications. I was pleased with the appearance of the mantle but the finish was rough feeling. It looks as if there are thousands of very small bubbles in the finish. I was hoping for the glass smooth finish that my cabinets have. I know that there are a lot of different contributing factors to the problem, but can you tell me what I did wrong? Would it make a difference if I used poly? Also, is there any way to correct the roughness other than taking it all off and starting over?

Rob Johnstone: I am not sure what is causing the little bubbles in your finish. You could try thinning your lacquer just a bit to start. When you spray the lacquer, be sure to get a nice wet looking application. (Don’t put it on too thick, or it will run.) That balance of getting a sufficiently thick layer of sprayed-on finish, without going too far and having the product sag or run has always been a challenge for me. It is one task that really aided by experience.

Michael Dresdner: What you did wrong was spray without a spray booth or fan. Spraying fast drying material creates overspray — tiny airborne droplets of finish that partially dry in air and then settle onto the newly sprayed surface. They will leave the surface rough and pebbly, sometimes as rough as sandpaper. You should always have a fan evacuating air as you spray, and you should be spraying toward the fan so that overspray goes away from the piece you are spraying. And that is merely the quality of finish issue — I won’t even start into the dangers you create by doing what you described.

Fortunately, you can smooth it to high gloss if the finish is thick enough. Sand it through the grits with very fine paper (from 400 to 1200), then rub with automotive gloss polishing compound.

Posted in: