How to Make Castile Soap Paste

Castile soap paste is the thick, concentrated base that becomes liquid castile soap once diluted. Making the paste yourself gives you full control over quality — and it stores well, so you can dilute batches as you need them. Here is the full method in under two minutes:

A quick safety note: lye is caustic. Always work in a well-ventilated space with gloves and eye protection, keep it away from children and pets, and add lye to water — never water to lye.

The method, step by step

1. Add the lye water. Pour your prepared lye water into the measured oils.
2. Blend to light trace. Blend the mixture until it reaches a light trace.
3. Cover the vessel. Cover tightly with plastic wrap.
4. Heat and begin gelling. Place the covered vessel over heat, using a double boiler or crockpot. Once it starts to gel, lower to the lowest setting and let the gelling progress without mixing.
5. Stick blend. When the mixture has fully gelled, stick blend until thoroughly mixed.
6. Finish cooking. Cover again and allow it to cook longer.
7. Cool and rest. Once the paste is translucent with a Vaseline-like consistency, turn off the heat and let it sit for at least 8 hours, or longer.

After resting, the paste is ready to use, package, or dilute into liquid soap. Diluting is its own step, and the water-to-paste ratio makes all the difference to the final consistency. Once diluted, if your soap is thinner than you would like, you can thicken it with HEC to a smooth, professional finish.