The news from the small river town of Saltillo, Mexico, is Earth-related but not earthshaking: The clay tiles that are the area's most famous export--and a popular flooring material for Arizona patios and kitchens--are going to be changing.

The reason? The tile makers fire their kilns with old automobile tires, a practice that the Mexican government has banned. The change to natural gas or other fuels will alter the appearance of the tiles--which are already handmade, one-of-a-kind items--and raise the price.

So say local tile retailers, who for months have been hearing about the change from their suppliers.

"What's happening is, Mexico is cleaning up its act," says Bonnie Munroe, a staffer at the Mexican Tile Company in Phoenix. "Which is good for everybody but us."
The process that results in Saltillo tiles starts with the area's clay soil which in its natural state resembles chocolate ice cream. The clay is mixed with water and pressed into wooden forms, then stacked, cured outdoors for several weeks, then fired in kilns that have been excavated into the banks of a river that runs through the area. (Saltillo is about 60 miles west of Monterrey, in Coahuila state, which adjoins Texas.)

Until recently the fuel for the three-day firing process has been shredded car tires and inner tubes. The high heat produced by the burning rubber eventually robs the kiln's interior of oxygen. The flame then goes to work on the next closest source of oxygen, the iron oxide in the stacked tiles, which burns and gives the tile its trademark peach coloring.

"That's what makes Saltillo tile distinctive," says Penny Wigley, who runs The Clayground ceramics studio in Phoenix. In Saltillo, burning tires is "a recycling thing, part of the way they've done things for years and years."
When Wigley visited the valley of the tiles in 1987 to see the process in action, she saw "miles and miles of tile. Some manufacturers had a large number of kilns. In other areas, a family will run just one."

A Saltillo kiln typically produces a small cloud of noxious black smoke. When several are working at the same time, the cumulative effect can be kind of scary. "It's the most incredible black thing you've ever seen in your life," says Munroe, who also has made the pilgrimage to Saltillo.

But the tile makers work independently, so its rare when more than two or three kilns are belching at the same time, Wigley says. "I wouldn't say there's a huge pall of black smoke," she adds. "There's usually a breeze through the river area, so it doesn't hang around. When they start firing and when they introduce more fuel is the only time they get that smoke coming off. You don't walk through clouds of smoke."

In Mexico, where environmental degradation usually is a way of life and antipollution regulation a rarity, the transition from rubber to gas fuel has been gradual. Still, says Karen Gosnell, Mexican Tile Company president, the changeover will eventually cause the price of the tile to increase. Some in the business predict the cost to double.

As for tile aesthetics, steps are being taken to ensure that the tile retains its peachy glow--a glow caused by the chemical reaction fueled by burning rubber.

"If they do completely change to firing with gas, it probably will alter the look of the tile a little bit," says Gosnell. "But we think they will still be able to throw a little rubber into their kilns to get that kind of color."