Tofu Mold: Build a wooden frame from finished 3/4-inch thick lumber. The open frame can be square (7-inches by 7-inches) or rectangular (8-inches by 6-inches) and have a height of 2-inches. Build a pressing board (removable top) from the same lumber. The dimensions of the top should be 1/2- inch smaller than the interior dimensions of the frame. Two cross pieces can be used to hold the board together in the event two or more pieces of lumber were used to make it. These cross pieces serve as handles to lift the board from the frame after the tofu is pressed. The cross pieces should be located one inch from the edge of the board.
Tofu: Stirring frequently, heat the strained soybean milk to 180 degrees, remove from heat source. A couple of different coagulants can be used to bind the soybean milk. The most commonly available is Epsom salt (magnesium sulfate), which can be purchased from drugstores. I have found that magnesium chloride works better. Mix the coagulant with 1/4-cup of water before adding it to the heated soybean milk. Pour the mixture into the hot soybean milk a little at a time and observe. The process is like thickening a sauce with a cornstarch slurry. The milk will begin curdling. The quantity of coagulant varies depending on the choice of chemical, the amount of soybean in the milk, and the desired firmness of the final product. If a soft tofu is desired, curdling should be minimal; the curdling milk in the pot can still be stirred easily. If a hard tofu is desired, the stirring becomes harder.
Put the tofu mold in the sink so the excess liquid can drain easily. Cover the inside of the mold with rinsed cheesecloth, allowing at least 6-inches of extra cheesecloth for each side of the mold. Pour the curdled soybean milk into the mold, then fold over the extra cheesecloth, sides first. Place the pressing board on top of the cheesecloth. Put a water-filled bowl or pot on top to exert pressure, remember that water is very heavy, a gallon of water weighs seven pounds. The position of the weight should be adjusted so pressure on the tofu is uniform. For soft tofu, a five-pound weight will be more than adequate - a pot plus two quarts of water will work fine. The final firmness is also dependent on time. For soft tofu, five minutes pressing will be sufficient. For firmer tofu, more weight and longer time will be required. When the tofu has reached the desired consistency lift the wrapped tofu from the mold and uncover it. Tofu can be divided and the pieces stored in water in the refrigerator of up to one week. Tofu can also be frozen.
Use a blender to make soybean milk in batches of one cup of soaked soybeans to three cups of water. Each batch should run for at least 3 minutes. Put the coarse soybean milk into a large pot and heat to a slow simmer. Cook for 10 minutes. Place a colander, covered with a clean kitchen towel, into a large pot or bowl. Pour the hot soybean milk into the towel to strain the soybean milk. A small amount of milk will drain via gravity; most must be forced out. This should be done when the milk has cooled. To do this, gather the edges of the towel to form a sealed ball. Tighten the towel edges like a screw. Use a spoon to scrape the outside of the ball to facilitate the flow. Make certain that the bean residuals are trapped inside the ball. Continue this process until the inside of the towel is nearly empty.