Q:

I recently refinished my bathroom with Mexican floor tiles left over from the house’s original construction about 10 years ago. I have been unable to find out how to seal these tiles. The original tiles were sealed on the job. My local tile supplier sells only presealed tiles and could offer no advice. At the time I purchased the house, I found a rusted can of what appeared to be a polyurethane-type finish stored near the tiles, but I couldn’t read the label. Can you please suggest a product or a formulation that I could use to seal these tiles?  

Walt Brewer, Catlettsburg, KY

A:

Robert Wilcoxson of Island Tile in Edgartown, Massachusetts, replies: First, I recommend cleaning the tiles with a solution of sulfamic acid and water. This may remove some of the grout stains and even the appearance slightly. It may also darken the tiles somewhat. After acid-washing, rinse the tiles with water and let the tiles dry completely before applying any sealer. If the idea of using acid makes you nervous, use a scrubbing pad, like 3M’s Scotch-Brite pad, and water.

If you desire a urethane-type finish, the sealer left on the job may be okay, but if it’s 10 years old, I doubt it. You can test the substance by applying it to a loose tile and letting it dry overnight. I use this method for checking the appearance of sealers. The sealer I use on Mexican terra cotta tiles is called Elon penetrating terra cotta tile finish (Elon, Inc., 5 Skyline Dr., Hawthorne, N. Y. 10532; 914-347-7744). It usually requires three or four thin coats to seal the tiles. Follow it with a heavy coat of liquid wax, and about a week later, a paste wax. The tiles will require paste wax every six months.

An alternative method, and the one that’s been used for years, is to seal the tiles with a mixture of one-half boiled linseed oil and one-half turpentine. Three or four coats will do. It is important that the coats be thin and that you allow drying time between coats. Butchers wax may be used on top of this.

I would recommend against stoning the high spots unless they pose a toe-stubbing problem. When the surface is sanded or stoned, it darkens considerably upon sealing. Again, a good way to experiment is with a loose tile to see what the results will be.