Authentic Saltillo tile is made in only one place in the world: Saltillo, Coahuila, Mexico. These tiles are unglazed clay floor tiles that local artisans make from the natural clay that surrounds the area. There are several methods of making the clay tiles and different quality levels of tiles. The workers make the tiles by mixing the clay with water, molding them, and curing them in kilns. The great demand for these artisan tiles has resulted in flooding the market with lower-quality tiles made from unclean clay.
The clay in the Saltillo area is some of the finest clay in the world. Craftspeople make quality tiles by using fine clay from the riverbanks. The worker sifts this clay to remove impurities and then mixes it with water to create a workable substance. There are several methods for forming the tiles, but all of the tiles are left to dry in the sun. The workers cure the sun-baked tiles in kilns.
The different methods of forming the tiles include two traditional methods and a method that uses metal molds. The two original methods are de agua and de golpe. In the de agua way, a worker places wooden frames directly on the ground and pats the wet clay into them. He or she lifts the frame away from the wet tile and lets it sun dry. To create a smoother, cleaner bottom, many workers put newspaper on the ground before forming the tiles.
The de golpe method makes a denser Saltillo tile because the artisan uses less water. Generally, this frame has a wooden bottom, making it more a mold than a frame. In the de golpe method, the worker inverts the tile onto the ground and then allows it to dry.
The pueblo method uses a metal mold. The artisan uses a thicker consistency of clay and water mixture and presses it into the mold. This method gives the least rustic appearing tiles.
After the tiles have air dried, workers cure them in kilns. Traditionally, the kilns were caves. After stacking the tiles in the cave, workers sealed the entrance with clay. A closely controlled fire at the other end of the cave heated the cave and dried the tiles. As the fire burns, it exhausts the oxygen in the cave and then it draws iron oxide from the tiles.
As the iron oxide burns, it causes a flash on the exposed surface of the tiles, which creates a lighter color on the tile surface. The areas where the tiles are stacked together are peachy-colored because these areas are shielded from the oxidation. Other color variations depend on the heat of the fire, the impurities in the clay, and color additives. Some artisans add manganese oxide, a natural brown colorant, to alter the tile colors. Sometimes the fire will cause a greenish color.
Lime pops are bits of alkali, or quicklime, that work their way to the surface of the Saltillo tile during the curing process. Small bits of lime are not a problem. Larger pieces may leave undesirable holes in the tile. A tile installer usually tries to cut this part of the tile away, but because this is not always possible, a person should order extra tiles to compensate for this problem. A homeowner should never use muriatic acid and vinegar on Saltillo tile because it will make the problem worse.
Despite the method that a worker chooses to use, the quality of the Saltillo tile depends on the cleanliness of the clay. When a tile maker uses riverbed clay or does not use a fine sifter, the resulting tile will have larger particles of debris. Often this debris weakens a tile. For high-traffic areas, homeowners should chose high-quality tiles.