- Recipes may vary, but the basic milk soap recipe calls for four parts vegetable oil shortening, 1/4 part cocoa butter, two parts olive oil or coconut oil, two parts milk, and one part lye. Supplies include a candy thermometer, a large stainless steel pot, two metal pitchers, soap molds, plastic wrap, a thick towel, tablecloth, old newspapers, white vinegar, and two large metal spoons.
- Lye is a very potent chemical and should be handled carefully. It's always wise to wear protective eye wear, rubber gloves, long sleeves, shoes, and long pants. If lye comes in contact with the skin or eyes it can cause burns or even blindness. White vinegar will neutralize lye, so make sure to have some handy. Protect the work surface with a table cloth and old newspapers. Keep lye away from children and do not breathe in the fumes that lye puts off. Have all equipment and supplies ready before starting. Do not leave ingredients unattended during the heating process. Allow plenty of time to make the soap. Haste can cause mistakes or accidental injury. Good ventilation through an open window is a necessities.
- Begin by melting the oil, cocoa butter, and shortening slowly over a low heat. Monitor the temperature of this mixture with a candy thermometer. Do not let this mixture rise to above 125 degrees or it could catch fire. Once melted, remove from heat. This mixture will need to cool to around 105 degrees. While this cooling takes place, carefully mix the lye into the milk. If you wish you can mix the milk half and half with water. Never pour milk over the lye, always add the lye to the milk. Slowly stir the lye into the milk until all dry particles have dissolved. A chemical reaction between the milk and the lye will begin to take place. The mixture will quickly begin to heat and will give off very strong fumes. The milk and lye mixture may get as hot as 300 degrees. This mixture must be allowed to cool to within five degrees of the oil, cocoa butter, and shortening mixture if the soap is to be successful. Carefully mix all cooled ingredients together and stir until mixture thickens. Do not heat this mixture. Once a thin coat of soap sticks to the spoon the mixture is thick enough. It may take a while to get to this point. Thankfully, the soap does not need to be stirred constantly. Just the occasional mixing will do.
- Place the desired soap mold on top of a thick towel. Pour the cooled soap into the mold and cover with plastic wrap. Wrap the towel up over the top of the plastic wrap and let the soap sit for at least 24 hours. You will probably notice heat building up inside the towel, but this is normal. When the towel is cool you can remove the soap from the mold. For best results, allow the soap to cure outside of the mold for three to six weeks.
