Liquid Castile Soap

liquid castile soap

Bottled liquid Castile soap


I’ve recently changed my liquid Castile soap recipe as I realised that I hadn’t been cooking the soap for long enough. I now cook it on low for 4 hours and then leave it in the slow cooker until the next day before storing.

The new recipe increases the amount of water and glycerine and reduces the amount of potassium hydroxide.

I also realised that it makes more sense to store the soap as a paste and then add water to dilute it as needed.

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 68ÂșC.

liquid castile soap

liquid castile soap paste


1000g olive oil
360g water
203g potassium hydroxide (KOH)
250g glycerine


  1. Weigh out the OIL into the slow cooker and set to LOW.
  2. Weight out the WATER and the GLYCERINE into a medium measuring jug
  3. Weigh out the POTASSIUM HYDROXIDE into a small measuring jug.
  4. Add the potassium hydroxide to the water/glycerine and stir well.
  5. Leave on an outside window sill for 10 minutes.
  6. Stir the mixture and then leave for another 10 minutes.until
  7. Add the lye solution to the oil and stir well.
  8. Blend with a stick blender for 15-20 minutes, stopping ever so often to stir the mixture with a spatula.
  9. When the soft trace stage is reached, cook the soap for 4 hours, blending with the stick blender every 30 minutes. If the mixture gets too thick for the blender, stir with a wooden spoon.
  10. Unplug the slow cooker and leave to cool until the next day.
  11. Transfer the soap paste to containers and store until needed.

1 litre of olive oil makes approximately 1670g of olive oil soap paste.


Mix 1 part soap paste with 3 parts water. To be on the safe side, first add 2 parts water and then gradually add the third to check consistency.