Weigh and combine tallow, coconut, and olive oil in a large stainless steel pot and heat over low heat until oils are melted. Cool to around 90 degrees Fahrenheit.
Weigh water and lye in separate containers. Outside, with protective gloves, goggles, and mask, slowly add lye to the water (be careful. Lye will burn your skin if it touches you. Don't inhale vapors either!). Stir. Cool to around 90 degrees Fahrenheit.
3.2 ounces lye, 9 ounces water
Pour lye water into oils and blend with hand mixer until light trace.