Diana Kennedy's book The Art of Mexican Cooking goes into great detail about making masa for tortillas and tamales. This is the condensed version:

Use 1 lb dried corn kernels, 1 cup water and 2 rounded tsp. powdered lime. Rinse corn, put in non-reactive pan with enough water water to come 1" above corn. Stir 1 cup water into the powdered lime and pour thru fine sieve into pan, pressing lumps with back of spoon. Cook until small bubbles appear on the surface--do not boil. Lower heat and cook until the yellow skin can easily be slougdhed off the kernels, test by rubbing a few kernels betw. fingers. About 15 min more. Let stand in the warm liquid for at least 12 hrs. and up to 48. Rub off all skins and send to the mill to be ground. (She shows a special corn grinder or says to use a metate and nano.) Do not overcook corn or it will make a tacky masa impossible to handle for tortillas.

From: Diana Kennedy's book The Art of Mexican Cooking
Posted By: Judy Howle
Flavors of the South, Recipes for "heat lovers"
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