Michael Dresdner

straight talk about wood finishing

The evils of over sanding

Q: I’m getting some shiny areas in the finish after four coats of satin lacquer, scuffing with 180 in between. The sealer over the pore filler is two coats of tinted garnet shellac. Over that is one coat of sanding sealer. I fear I’ve sanded through the lacquer and gotten down to either the tinted shellac or the sanding sealer during my scuffs and that’s why I’m getting these shiny spots. A: It’s possible. Scuffing means sanding very lightly with 320 or 400 paper, not 180, which is coarse enough to cut entirely through the finish. Incidentally, there is absolutely no reason to scuff between coats of evaporative finishes like shellac or lacquer, since both dissolve the prior coat. The only reason to sand is to remove dust nibs or if you leave brush or spray marks in the finish, and even then you can usually wait until just before the final coat with evaporative finishes. It is also both unnecessary and counterproductive to apply both shellac and sanding sealer. Use one or the other as a sealer; preferably dewaxed shellac. In many cases, neither is needed. For now, stop sanding between coats, add two more coats of satin lacquer, then let the finish cure fully and rub it out to get a uniform sheen.
If I may be so bold, from the tone of your questions I’d say you need to learn some more finishing basics. Therefore, I’d suggest you read The New Wood Finishing Book, which is set up as a comprehensive step by step course in finishing. You can find it on my book and video page. It will give you a good grounding in finishing and help you avoid both unnecessary steps and errors.