What is Superfat in Soap Making?

A superfat is an excess of butters and oils in a finished bar of soap that have not been saponified and turned into soap. You can create a superfat in your soap if you are making cold process or hot process soap, but not with melt and pour soap.

Superfatting is a great thing. A finished bar of soap with a superfat is beautifully luxurious and moisturising.

How to superfat soap?

To create a superfat in your soap, you need to use the right amount of sodium hydroxide to saponify most of your oils but not all.

Generally we superfat to around 5%, which means that every bar of soap will have 5% of excess oils. You can use an online calculator to work out the quantity of sodium hydroxide needed to saponify 95% of your butters and oils leaving the remaining 5% as a superfat.

Can I choose which butters and oils form my superfat?

Generally, no. In cold process soap making all the oils are added in at the start of the process, so it is not possible to choose which are used to superfat. 

With the hot process method however you absolutely can choose which oils form the superfat. Withhold your chosen superfat oils until after your soap is cooked and saponification is complete. Then add them in at the end when the sodium hydroxide has all been used.

This is a great method to use if you like to use a luxury oil as your superfat.

Will superfatting make my soap bar soft?

Yes, it will. This is why generally we only superfat to around 5%. For most recipes this will give a moisturising but still hard bar of soap.

There are exceptions though.

Coconut oil soap can be drying as it has a high cleansing value but it also makes an extremely hard bar of soap. It is possible (and advisable) to superfat a 100% coconut oil soap up to 20 or even 25%.

This will still create a very hard bar of soap but the high superfat will also compensate for the drying effect of coconut oil soap. It makes a surprisingly lovely bar which lasts well in the shower.