Bring soymilk to a boil in a pot on the stove. Turn off the heat and let cool to between 180 - 200 degrees F.
Dissolve 1 teaspoon of nigari into 1 cup of warm water.
Slowly pour 1/2 cup of nigari solution into the pot of soymilk and lightly stir. Wait 2 - 3 minutes and add more of the nigari solution until the soybean curd separates from the liquid.
Strain the water from the curd and press into a mold to drain. The more you press the liquid out of the tofu the firmer it becomes. Be sure to press the desired amount of moisture out of the bean curd before it cools.
Use immediately or store in water in a covered container in the refrigerator.