Q. I varnished a table with a satin-finish polyurethane product. After it dried, some areas were glossy while other areas were nearly matte flat. What caused this to happen, and can I repair it?
A. Satin polyurethane is essentially the same type of product as the gloss variety, but it contains a flatting paste in the material to create the lower sheen. Because clear urethane products have very low viscosity, some of the flatting paste tends to settle to the bottom of the can. For this reason, it is important to stir the product frequently as you work to ensure greater uniformity of sheen. If the finishing product was applied without being adequately stirred, the resulting sheen will likely be inconsistent as you described. To fix this, allow the clear coat to dry completely. Lightly sand the work surface to dull the existing finish and promote better adhesion of the following coat. Then, apply a thin, final thin coat of the satin product. Be sure to stir frequently when applying to ensure the final finish is consistently satin throughout. (Information courtesy of Sherwin-Williams)