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 68ºC.

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.

Video of wrapping soap

Sarah has now become an expert soap maker and has gone into large scale soap production. We have been selling boxes of 6 soaps in Spain and also around Europe.
We have so far only sold soap to people we know.

We even have an Etsy and a Wish page.

Sarah invented and designed this system to wrap the soaps using a wooden template. 

See the other page about soap making here

Soap Making

The aim of this blogpost is to chart, document and record my attempts at soap making.

There are hundreds of videos online but I found Everyday Elly’s ones (for sourdough and soap) particularly helpful for general information about soapmaking, and how to calculate quantities, store and cure soap, etc. Here is a link to her YouTube channel: Elly’s Everyday.

Soap made from pure olive oil is called Jabón de Castilla or Castile Soap. Years ago, when we lived in the Sacromonte area of Granada, Consuelo our neighbour would sit in the street outside her house stirring a large vat of leftover oil mixed with caustic soda. Any oil would do she told me and it would make a pure soap that you could use on your skin or clothes. 

The second time, I made soap I used the proportions suggested in Elly’s Everyday for Castile Soap:

600g olive oil
109g water
79g caustic soda

The important thing is to add the LYE to the water and wear safety goggles, mask and gloves while making the soap. 

The total weight of the soap made was 788g and this was enough for 7.8 bars of soap made in the silicone moulds.

The percentages for each ingredient are:
76.14% olive oil
13.83% water
10.03% caustic soda

I have calculated that each mould holds 105g so the quantities for one bar would be:
80g olive oil
14.5g water
10.5g caustic soda

The quantities for 4 bars would be:
320g olive oil
58g water
42g caustic soda

The first time I made soap with this method, I placed boards below and on top of the mould and wrapped it all up in a large towel. This supposedly helps the saponification process and ensures that the bars saponify evenly.

I took the bars out of the moulds on the morning of the third day after I had made it. They were all OK except for one so in the future, I will remove them from their moulds after 3 days.