Place the 2 1/4 cups of corn in a colander and rinse. Remove any debris.
Dissolve the 2 tablespoons of calcium hydroxide into the 12 cups of water in a large soup pot or Dutch oven. Add the corn.
Bring to a boil over high heat then reduce the heat to medium-low and simmer, stirring occasionally, for 1 hour.
Remove from the heat and let steep for 16-18 hours.
Drain and rinse to wash off the dissolved outer skin that is now like sludge on the corn and in the pot. At this point you can use the corn to grind into masa for tortillas or tamales. If you want to use it for pozole, you need to keep cooking it to make it more tender.
Wash out the pot you've been using and return the corn to the pot. Fill the pot with water and add the 1/4 cup salt and 1/2 an onion.
Bring to a boil then reduce the heat to a simmer and cook until it's reached desired tenderness. I like it to retain some bite, like al dente pasta. This could take another 1-2 hours.
Drain, discard the onion and use to make pozole or your favorite recipe.
If not using right away, store in an airtight container for up to a week or freeze for up to 6 months.
