How to Make Organic Liquid Castile Soap Without Lye

Heather Dewar

Castile soap is a mild soap made from vegetable oils. The soap, which comes in both bar and liquid forms, originated in Spain and was made exclusively with olive oil. Today, olive oil is often replaced or used in conjunction with other oils like coconut and soy when creating Castile soaps.

Organic Castille soap is often recommended for babies and individuals with sensitive skin.

Although Castile soap requires lye (potassium hydroxide) as an ingredient in its creation, a process called saponification converts the lye and vegetable oils into a new compound, resulting in a lye-free end product. To ensure your soap is organic, choose certified organic oils.


To save money, substitute a portion of the olive oil with organic soybean or organic coconut oil.


Potassium hydroxide is a caustic chemical that produces heat when mixed into water. Always use protective rubber gloves and goggles when handling this substance.

  1. Turn on the crockpot and set it to the highest heat setting. Add the 47 ounces of olive oil to the crockpot.

  2. Put on gloves and goggles. Add 32.9 ounces of the distilled water to the heat-safe container. Mix in 9.39 ounces of KOH flakes to the distilled water.

  3. Slowly pour the KOH flakes and water mixture into the oil in the crockpot, using a heat-safe spoon to stir.

  4. Stir the oil mixture off and on for about 90 minutes, until the mixture is so thick and rubbery that it's almost impossible to stir.

  5. Lower the crockpot setting to medium, put a lid on it and let the mixture cook for 90 to 150 minutes, stirring every 20 to 30 minutes until all the soap is translucent.

  6. Boil 1 cup of distilled water. Add a tablespoon of soap to the boiled water. If the water is clear after the soap dissolves, then the soap is done. Otherwise, continue cooking until a sample of soap in boiled water becomes clear.

  7. Transfer the soap into a large stainless steel pot. Boil 80 ounces of distilled water in a separate large pot. Pour the boiled water into the soap and let it sit overnight to dissolve.

  8. Transfer the dissolved soap and water mixture into jugs and let them sit for four weeks.