The LA Times has an article about making tofu at home that is "exponentially better than any store-bought blocks of tofu" with soy milk and nigari brine.
This is [Sona restaurant chef de cuisine Kuniko Yagi's] recipe for making tofu from soy milk, and it's the one Yagi uses: Add a teaspoon of liquid nigari to 500 milliliters of cold soy milk and stir. Then pour it into heat-proof bowls and cook (in a water bath or steamer) until it sets like custard. That is it. There's no heating the soy milk to bring it to a certain temperature before adding the nigari. No separating liquids from solids. No straining once it's cooked.
Kariya had figured just the right amount of soy milk (which he makes — so he knows that the brix, or percentage of dissolved solids, is 14%) to use with a certain amount of nigari (which he imports from Japan and has magnesium chloride and other trace minerals), so that his tofu recipe works consistently. He sells both the milk ($3.50 for a half-gallon) and the nigari, which isn't cheap but will make a lot of tofu and will last almost indefinitely ($25 for a pint).
