Calculating CP soapmaking recipes

Handmade soap is made with water, oils and sodium hydroxide. Sodium hydroxide is a very dangerous chemical.

When the ingredients are calculated correctly, no sodium hydroxide remains in the soap.

There is not a soap/beauty bar in the world that does not contain sodium hydroxide, despite what marketing teams would like us to believe.

These days we are very lucky to have lye calculators online to help with soapmaking recipes.

Go to our lye calculator and have a play.


Decide what oils you want to use: We will use coconut oil, organic  palm shortening (from sustainable sources) and olive oil as an example.

230g coconut oil
230g palm shortening
230g olive oil

So on the lye calculator we will put 230 beside those oils and press Calculate.
It comes up with about 105g sodium hydroxide and 230g water.

So there we have a recipe:

230g coconut oil
230g organic palm shortening
230g olive oil
228g water
105g sodium hydroxide

Essential/fragrance oils are added at between 1% and 3%. Price usually determines what percent.
To calculate how much to use, add up the weight of all the oils and water.
In our recipe above that is 230g x4 = 920g.
1% of 920g is 9.2g
3% is 27.6g.
Use as much as you can afford as the odour does evaporate over time.
Some essential oils are better than others but generally they need to have quite a strong perfume to be effective.
Always store handmade soaps in an enclosed container or packaging. This will reduce the evaporation of the essential oils.

Colour can be added to the recipe and this can be tricky.
Because of the chemicals used, a colour that looks a gorgeous can turn out like nothing or could even turn a completely different colour.
Only experimentation can help with this.

Moulds
CP soap works better in block moulds because the saponification process needs heat to work. In a block mould there is more chance of this happening. Soap made in small single cavity moulds often turns out crumbly.

Many everyday items can be used for moulds: cardboard milk cartons, icecream containers, etc.
It needs to be sturdy enough to hold the soap while it is hardening over 24 hours.
The mould needs to be flexible so the soap will pop out.
If you are in doubt then line the mould with baking paper, or put the mould in the freezer for 30 minutes and the soap will shrink enough to pop out.