How to Make Tallow Soap:
When making tallow soap, or any true soap, you must use an alkaline ingredient called sodium hydroxide or potassium hydroxide. This ingredient, also called lye, was traditionally harvested by steeping hard wood ash in a pot of water. Today, you can source dry sodium hydroxide beads locally or online.
To use this ingredient properly and safely, always dissolve the solid form lye, sodium hydroxide or potassium hydroxide, into the liquid little by little as specified in the recipe below. If the liquid was poured directly into a cup of the solid form lye, a violent reaction could result. This means you could have a "volcano" erupt out of your container.
Lye can be dangerous if not properly handled, however, soaps made with the right ratio of fats to lye are safe to use on the skin after they have been properly cured. When water, lye, and fats are combined and emulsified, this triggers a chemical reaction called saponification which turns the mixture into a washing salt and glycerin (hydrating soap) with no harsh lye left in the soap.
It is important to always follow a vetted recipe or use a soap calculator like this one (Lye Calculator - TheSage.com) when making soap to ensure your lye to fat ratio will result in a soap bar that is safe for your skin. Once the soap has cured for a period of 2-4 weeks, pH testing strips can work as a safeguard to determine if the soap is safe for use.
