Choose dried field corn or dent corn
Remove any debris and damaged kernels
Rinse the corn thoroughly
Make a cal solution by dissolving food-grade calcium hydroxide in water
Boil the corn in the cal solution
Simmer until the outer hull loosens
Turn off the heat and let the corn soak overnight
Drain the corn
Rinse the corn several times until the water runs mostly clear
Rub off loosened hulls by hand
Drain well
Dry the nixtamalized corn completely
Grind the dried corn into a fine flour
Sift the flour to remove coarse particles
Regrind any coarse particles
Store the masa harina in an airtight container