It isn’t always easy to tell if a wood table has been finished with varnish or lacquer, but it makes a difference when the time comes for refinishing. You shouldn’t refinish a lacquer finish with varnish, and vice versa, because the two materials behave differently. Lacquer softens and amalgamates into fresh material, but varnish cures and never gets soft again. Once you’ve determined that your old finish is varnish, you don’t necessarily have to strip it before applying another coat to freshen it up. If the old material isn’t peeling, scuff-sanding quickly gets it ready for a recoat.
Test the finish by moistening a rag with lacquer thinner and dabbing the solvent in an inconspicuous place. Feel the finish afterward; if it feels sticky, it’s lacquer, and if it stays hard, it’s varnish.
Clean the table with a rag soaked in mineral spirits to remove old wax. Run the solvent on a small part of the table until the rag turns dark, then rearrange the rag and keep rubbing. Do this until there is no more discoloration on the rag. If you leave wax on the table, new varnish won’t adhere.
Wash the table with a solution of strong detergent, such as trisodium phosphate, and warm water. This cleans dirt off the finish and, more important, it etches the old finish so that the new one adheres better.
Let the table dry thoroughly, then scuff-sand the finish with 150-grit sandpaper. You don’t need an orbital sander to do this properly; just fold a piece of sandpaper into thirds and do it by hand. Wipe off all the sanding dust with a clean rag.
Brush on a coat of polyurethane or alkyd varnish. If you use a solvent-based product, apply it with a natural-bristle brush, but if you use a water-based product, spread it with a brush that has synthetic bristles. Natural bristles swell and become limp when exposed to water.
Wait eight to 12 hours for the varnish to dry, then scuff the table with 220-grit sandpaper and apply another coat. Let that coat cure for several days, then rub it down with 0000 steel wool and apply a coat of furniture polish or paste wax.