The traditional U.S. version involves soaking dried corn in lye-water (sodium hydroxide or potassium hydroxide solution), traditionally derived from wood ash, until the hulls are removed. Mexican recipes describe a preparation process consisting primarily of cooking in lime-water (calcium hydroxide). In either case, the process is called nixtamalization, and removes the germ and the hard outer hull from the kernels, making them more palatable, easier to digest, and easier to process.