Dried kernels cook at or near boiling in an alkaline bath of slaked lime and water, then steep for anywhere from minutes to about a day. The alkali dissolves the glue-like hemicellulose in the hulls, the starch swells, and calcium soaks into the grain.

Factories drain off the yellowish cooking liquid, called nejayote, because it tastes unpleasant. The kernels are washed and big plants strip the loosened hulls off by machine, leaving cooked grain called nixtamal.

Wet nixtamal is ground into a fairly dry dough. Many factories instead dry and powder the dough into masa harina, then add water back when they need it.

Sheeters roll the masa into a thin, even band and die cutters punch out triangles or discs. Machines of this kind can turn out 30,000 tortillas an hour.

The cut dough passes over hot plates or through an oven, the same step that turns masa into a tortilla. Baking sets the shape and dries the surface before the oil.

The pieces drop into vegetable oil, where water flashes off as steam and the chip turns crisp. Some lines bake the chips a second time instead of frying them.

Chips tumble under a fall of salt or seasoning while the surface is still oily enough to hold it. Chips meant for dipping usually get only a light dusting of salt.