Castile Olive Oil Liquid Soap Recipe

This is my recipe and method for making liquid soap from the extra virgin olive oil we produce on our cortijo. This type of soap is also called Castile soap. The ideal temperature for making this liquid soap is 70ºC-80ºC.

1000g olive oil
312g water
208g potassium hydroxide
208g glycerine


  1. Weigh out all the ingredients before you start, weighing the olive oil directly into the slow cooked and the water and potassium hydroxide into separate plastic measuring jugs.
  2. Heat the olive oil on HIGH in the slow cooker to 70ºC. Use a temperature sensor to let you know when it has reached this temperature.
  3. Add the potassium hydroxide to the water and mix well. Leave on an outside windowsill until it goes clear.
  4. When the oil is hot, add the lye solution and stir well.
  5. Add the glycerine to the oil in the cooker.
  6. Blend with a stick blender for 10 minutes, stopping ever so often to stir the mixture with a spatula.
  7. When the soft trace stage is reached, turn down the cooker to WARM and leave to cook for 30 minutes, turning the crock pot 180º after 15 minutes to ensure that it heats evenly through.
  8. Add 3 litres of water and leave the cooker on LOW for a couple of hours.
  9. Stick blend to mix well.
  10. Leave to cool before pouring into bottles.