Wipe-on Poly and Blotching

[David Weaver]

Does anyone have an opinion about what finishes go on with the least blotching?

I made a cherry bookcase with a lot of solid trim, and the top is solid, or at least a very thick veneer that I made instead of using a thinner veneer.

I think the finish that's going on it looks a little bit blotchy - but only on the veneer piece - not the solid rails for the sides. Previously, I've used dewaxed shellac as a base and put the wipe on poly on it, and didn't have the problem, but maybe it's the wood I'm using. The veneer piece and the sides aren't from the same supplier, and the sides are a little clearer straighter grain. I'm afraid that the cherry ply carcass will have the same blotchiness when I get to it, and I'd really like to avoid that if possible.

Has anyone here done side-by-sides comparing the dewaxed shellac as a sealer versus just putting the wipe-on poly on? I don't have any scrap handy to do this, or I'd just do a test piece. I don't want to sand off the poly if the shellac base will look the same.

The poly I'm using is Rockler satin finish wipe-on, and everything is sanded to 400 grit.

[Steven Wilson]

Dewaxed shellac as a sealer (no poping the grain with BLO first) is the least blotchy finish I know for cherry. I do find that cherry plywood tends to be a lot more blotchy than thicker structural elements. I would imagine that an oil based poly (or really any oil based finish) would be fairly blotchy, just like applying a BLO/Tung/Turp brew to pop the grain does. The way I try to control the blotchies associated with an oil coat is to vary the ratio of solvent (turpentine in my mix) - adding a bunch when applying to plywood or figured cherry. Preflooding with solvent can also work to control the blotchies. I would suggest that you try various things on scrap wood before you apply them to your project. You could also try applying a waterborn coating and see what that does for you (maybe add a bit of amber tint to get the effect of an oil based finish) although it may look a little bland. You might also want to try suntanning a few pieces of scrap and seeing if that natural darkening produces less blotchies when applying your top coat.