How to Choose a Fragrance Oil for Cold Process Soap?

fig swirl CP soap

We have only recently realised that some of our fragrance oils are suitable for cold process soap.  Fragrance oils are not all created equal, so how can you know that a particular fragrance oil will work?   And what does “work” mean?

What is Cold Process Soap and how is it different from shop soap?

Cold Process soap, or CP soap, goes by many names including Natural Soap.  Cold Process soap is the result of blending vegetable oils or animal fats with sodium hydroxide, a.k.a. lye, also known as drain cleaner.   When you mix an oil with a strong alkali you set off a chemical process called saponification, the end result of which is soap.

Cold Process soap can be made at home because it requires no special equipment and the ingredients are readily available. Industrial soap, on the other hand, contains ingredients which you won’t easily find at Checkers or the hardware store.  In addition, industrial soap is manufactured with the most cost effective raw materials.  You’d be unlikely to find an industrial soap based on luxury ingredients like olive oil.

When does a fragrance oil “work”?

Experienced soapers can work with almost any fragrance but it’s certainly much easier if the fragrance oil does not affect the soap mixture in any unexpected way.

Common complaints against fragrance oils

Some fragrance oils accelerate trace, especially at higher temperatures.  What is trace?  Simply put, trace is a point in the soap making process when oils and lye water have emulsified. Once the soap has reached thin trace, it will continue to thicken over time. Mixing lye water and oils together starts the saponification process.  Thanks Soap Queen!

Fragrance oils can also cause ricing.  What is ricing?  Ricing occurs when an ingredient in the fragrance oil binds to harder oil components in the recipe to form hard rice-shaped lumps in the soap batter.Ricing can be stick blended or whisked out if necessary.

The most disliked fragrance oils cause the soap mixture to seize.  What does seize mean ?  The chemical reaction (saponification) between the lye and the oils you are mixing has fast-forwarded/overreacted itself into a big, thick mess.

Vanilla and fragrance blends which contain vanillins will discolour the soap mixture.  If you’ve added colourants such as oxides or micas these will be affected by the darker soap mixture.  That is, if your soap mixture turns brown but you’ve previously added ultramarine blue, your soap will end up being very dark indeed – and certainly not blue.

So how do you choose a fragrance oil for natural soap?

It is important to check whether the fragrance oil has been tested in CP soap and also to get as much information about performance as possible.  Take a look at the Candle Deli fragrance oil descriptions, you’ll notice that we indicate what you can expect from our fragrance oils.