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January Makealong: Castille Soap

January Makealong: Castille Soap

Every month, in our Farm School, we focus on a new skill or topic. January is all about natural cleaning. This weekend, we are making castille soap on Instagram and Facebook Stories.

A good castile soap is a powerhouse of natural cleaning. Traditionally made just out of olive oil, it can come in hard or liquid soap varieties. Its the liquid soap we are making today and of any recipe on this course, it has been the one that has transformed my home and saved me a ton of money. To buy the most popular castile soap on the market, Dr Bronner’s, costs about £15 per litre. The recipe below will yield about 1.4kg of paste which will make up 11 litres of soap. Using very high quality oils, the recipe below cost me about £14, not including energy and time:

  • £7 extra virgin olive oil

  • £3 coconut oil

  • £4 potassium hydroxide

All in I save about £140 with making my own!!

Recipe (printable PDF available below):

Homemade Castile Soap 


680g olive oil 

425g coconut oil 

205g potassium hydroxide lye flakes 

680g distilled water, for lye-solution 

Make the soap paste

1. Add the olive oil and coconut oil to a large slow cooker. Melt the oils on high.

2. While the oils are warming, using proper safety equipment, carefully measure the potassium hydroxide lye into a stainless steel or glass bowl (NOTE: NEVER USE ALUMINIUM WITH LYE).

3. Measure the water into a medium stainless bowl or glass pitcher. Set the container with the water into your sink, then very carefully tip the lye flakes into the water. Stir to dissolve.


4. When the oils in the crockpot are warm, carefully tip the lye solution into the oils. Leave the crockpot on high.

5. Use an immersion blender, blend the oils and lye solution together. Immediately after adding the lye solution to the oils, blend for about 5 minutes, until the mixture looks uniformly opaque and begins to slightly thicken. For the next 30 minutes, come back and blend the soap paste about every 5 minutes. The mixture will get thicker and thicker, progressing through an icing texture to something like PVA glue.

Cook the Soap Paste

1. When the soap mixture becomes too thick to blend with an immersion blender, lid the crock pot and cook the soap mixture for 3 hours on high.

2. Every 30 minutes or so, come back and fold and stir the soap paste with a heat-resistant silicone spatula or heavy wood spoon to ensure the soap paste cooks evenly.

3. As the soap cooks, it will become increasingly translucent, moving from a runny white liquid to a puffy taffy texture to, eventually, a yellowy-clear, thick, translucent gel.

Test Soap Clarity

1. After 3 hours, or once the paste looks fully translucent and gelled throughout, check the soap with a clarity test.

2. Measure out an ounce of soap paste (about a golf-ball sized blob will do it). Add 4 oz (1/2 cup) of boiling or very hot water to the soap paste. Stir gently until the soap paste is totally dissolved.

3. Allow the diluted soap to cool. If the soap is opaque, or if a scum of oil floats to the surface, continue cooking your soap paste for another hour before re-testing.

4. If the diluted soap is clear (it needn’t be colourless, just translucent), proceed with dilution.

Diluting the Soap Paste 

NOTE: I store my soap paste before diluting it.  I then follow the method below using about 10 parts water to 1 part paste for using as soap.  I also will scent it at this stage.

1. Add 10 cups water to the soap paste in the slow cooker. Break up the soap paste into the water as best you can but don’t worry about the paste dissolving fully.

2. Lid the crock pot and turn the heat to warm for 8 hours or overnight. If you happen to walk by, give the soap a stir to help it along but don’t worry if you can’t.

3. After 8 hours, if you notice chunks of remaining soap or thick skin of soap forming even after the chunks of soap dissolve, add another cup or two of water to further dilute the paste. 

When your soap is fully dissolved with no chunks of soap paste remaining, ladle your dilute soap into clean and dry glass or plastic jug.

When it comes to use it, dilute the soap further to about 1 part soap to 5-6 parts water.

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