Varnish, often used as a finish on stained wood, prevents the stain's colour from fading and protects the wood's surface. Varnish should not be used on tile, but in the process of varnishing a nearby wood surface, spills may occur. Varnish shares many of the same characteristics of paint and can be removed with a paint stripper. If dealt with quickly, varnish also can be removed with a simple, less toxic solution.
Combine one part TSP (trisodium phosphate) and two parts whiting (calcium carbonate) in a plastic cup. Add enough water to make a thick paste. Stir constantly with a wooden stir stick until you reach the desired consistency.
Spread the mixture over the varnish on the tile using a putty knife to create an even layer 3/8 inch thick. Allow the paste to sit on the tile, dissolving the varnish, for 30 minutes.
Remove the paste along with the dissolved varnish with a plastic putty knife. Scrape the knife along the surface of the tile using a moderate amount of force to remove as much of the mixture as possible.
Rinse the surface of the tile with clean warm water and pat the tile dry with a clean dry cloth.
Substitute a chemical paint stripper for the DIY stripper if the DIY mixture does not dissolve the varnish.
Protect yourself during the varnish removal by wearing rubber gloves and safety goggles. Only work within a well-ventilated space.