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David: CABINET-FINISH PROBLEM
Question: On my cherry entertainment center, I put a glossy water-based polyurethane over a water-based stain. But even after multiple coats, the brushstrokes are still evident. How can I get a nice, smooth finish?
-John Stevens. Maryville, Calif.
Norm Abram replies: Finishes can be tricky. Temperature, humidity, timing, the type of wood, and the brushes you use all affect the results. In your case, I think the problem is related to how you prepared the cherry or applied the polyurethane.
Before I use a water-based stain or poly, I sand hardwoods in stages up to 220 grit. Anything finer burŽnishes the surface, so it won't accept stain. Next, I spray the surfaces with distilled water, to raise the wood grain. (Tap water may contain minŽerals that stain wood.) After the wood dries, I give it a very light sanding with 220 grit-just enough to knock the grain back
down-tack it clean, and apply the stain. WaterŽbased finishes tend to raise the wood grain, so I lightly sand the surface again after the stain dries. I'll repeat the process until the wood feels smooth 'and I'm satisfied with the way the stain looks.
Now I apply the poly. Water-based polyurethanes dry very quickly, so I prefer to spray rather than brush them on. But when I do brush them, I use foam brushes and just a few strokes at a time to minimize the chance of stroke marks in the final finŽish. I also sand lightly with 220-grit paper between each coat and tack off the surface to ensure good adheŽsion of the next coat.
With your cherry project, I'd sugŽgest that you brush on a few more coats of poly, sanding lightly beŽtween coats, and then smooth away the brushstrokes using a sanding block. Take care not to sand all the way through the poly and down to the stain. When you are satisfied that everything is smooth, lay on one last coat using a foam brush, and the finŽish will be as smooth as it can be.