How to make Castile Soap

We want everyone to enjoy the benefits of natural soap, so we’re sharing this Castile soap recipe. It gets its name from its home town in 11th century Spain. This soap is a popular choice for sensitive skin types because it’s very mild and moisturising. This recipe makes 1.3KG of soap.



If you live in Australia, you should be able to find all of these ingredients in your supermarket:

1000g olive oil

375ml spring water

123g sodium hydroxide



kitchen scales



2 x 1L empty milk containers

baking paper

glass jug


large mixing bowl

spatula/mixing spoon

stick mixer


Protective Equipment


Sodium Hydroxide can burn your skin and eyes very badly – have you seen Fight Club?? It is very important that you take precautions to ensure it doesn’t come into contact with your skin or eyes. You will need to cure the soap for 4 weeks before use, to allow the sodium hydroxide to combine with the olive oil. When sodium hydroxide merges with olive oil, it creates sodium olivate. This is called ‘saponification’. Sodium hydroxide won’t exist at all in this soap by the end of the curing process because there’s more oil than is needed for saponification.

Be ready for the sodium hydroxide fumes when it’s initially mixed with the water. Make your soap in a well ventilated spot and use a fan if you have one.

safety glasses



Preparation Stage

1. Prepare an ice bath by filling a large container with water and adding ice cubes or packs.

2. Line the milk container with baking paper and secure with sticky tape.

3. Measure oil and add to the saucepan.

4. Measure water and add to the glass jug.

5. Measure sodium hydroxide.


Heat Stage
1. Place the jug of water into the ice bath. Pour the sodium hydroxide into the jug with the water and step back for a minute while the fumes evaporate. Do not breathe them in because they’ll burn your lungs. Stir until dissolved.

watertemp2. Heat olive oil on the stove up to 50°C and bring the sodium hydroxide down to 50°C. It doesn’t have to be exact, but make it pretty close.





Mixing Stage
1. Pour the oil into the large bowl and add the sodium hydroxide solution.

2. Stir with the spatula or spoon to combine, then use a stick mixer. If you don’t use a stick mixer, you’ll be literally stirring for hours. You can stop mixing when the soap reaches ‘trace’ which is so called because the soap is a consistency of pouring cream and leaves a trace when you trickle some over the top.

Mixer3. You can add 30ml of essential oil at this point if you like.

4. Pour the mixture into the lined milk containers and leave to set overnight in a cool place out of reach of pets and children.




Cutting Stage

CuttingSoapIf you’ve done everything right, your soap should be hard enough to take out of the mold and cut. It can take up to 2 days to harden. If you’re having issues, leave a comment on the Facebook page and I’ll try to help you.

1. Using a sharp knife, cut your soap and place the slices in a cool place where they can cure for 4 weeks. I use a mitre box (pictured) for even cutting.


Handmade soaps make great gifts – share it with your friends!

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