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Q.A past customer purchased Mexican Saltillo tile from a distributor and had it installed by a tile installer I referred her to. The tile came presealed and was installed — per instructions on the shipping boxes — using thinset mortar. Within a day or two, the sealer began to fail, appearing as a milky white coating on the surface of the tile. There appears to be moisture in the tiles themselves: Could it be that the sealer was applied to tiles that were not completely dry?

A.Tile-setter and JLC contributing editor Michael Byrne responds: Saltillo pavers have always been among my favorite tiles because of their unique handcrafted appearance. I have used a wide variety of colorants and sealers on them, including aniline dyes, opaque stains, penetrating oil, hot paraffin and naphtha, beeswax, and other materials that do not react with water.

The few times I’ve seen problems with a cloudy finish, the culprit was latex sealers, which are not intended for exposure to damp conditions. The cloudy haze appears when latex in the sealer begins to re-emulsify. Although I can’t be sure without examining them, I would guess that this is the problem with your tiles. Since they were fired before they were sealed, it’s highly unlikely that any moisture left over from the tile-forming process still remains in the body of the tile.

The cure is to identify the sealer, strip it with a safe, compatible stripper, and reapply an approved colorant and sealer. Unfortunately, it’s probably impossible to find anyone who can tell you what sealer was used. This is because Saltillo pavers are made by families who sell to brokers who sell to larger brokers who sell to exporters who sell to distributors who sell to dealers. Since there is no industry standard for Saltillo pavers, it’s always a matter of “buyer beware” — especially with presealed pavers.

I suggest that the installer contact the tile dealer and show him the problem. If the dealer is not helpful, ask for a few sample tiles to test. Go to the local paint store and buy a stripper designed for latex coatings. Try it out on a leftover or sample tile, or on an area of the floor that is out of sight. Be cautious, because using the wrong stripper may make the situation worse by discoloring the tile or driving the sealer in deeper, making restoration to the original tone and sheen virtually impossible. Good luck.