Soapmaking for Beginners: SAP Values Explained

If you have researched soap making, then you have probably seen a SAP Value list.  While it looks very overwhelming to start with, they can be one of the best tools to use when developing your own soap recipe.  This definitely will not be our most exciting blog post, but understanding SAP Values will help you when you want to formulate.

To start with, the SAP Value is simply tells you how many ounces of lye are needed to turn 1 ounce of oil into soap.  

Example - If an oil has a SAP value of .184, the you would need .184 ounces of lye (NaOH) to react with 1 ounce of that oil.

You may also see some SAP charts that list values for NaOH (Sodium Hydroxide) as well as values for KOH (Potassium Hydroxide).  If you have multiple values, just double check that you are using the correct one for your lye.  Sodium Hydroxide is what we use to make bar soaps and you would use KOH to make a liquid soap base.  Some shaving soap recipes will call for using ratios of both to create dual lye soap bases.  

In the chart below, you will also see a column for the predominant fatty acid profile of each oil.  These different profiles are what determine how the oil impacts your final bar of soap.  For example, stearic and palmitic influence the hardness of your soap, while oleic increases the conditioning.  While it might sound nice to make bar with just conditioning oils, you would end up with a soft bar of soap that would dissolve quickly in water.  True castile soaps are usually made with just olive oil and to get a usable bar, they will need to cure for months if not years.  

Because every oil has a different fatty acid composition, each one reacts with lye differently—this is why you can’t just swap oils in a recipe without recalculating your lye.  You may see recipes online that say to use olive oil or some other oil in the same amount.  These substitutions may be okay, but it is always a good idea to double check the SAP Values to make sure they are the same before substituting any oils.  We also recommend running any recipe that you find through a lye calculator prior to using too.

Calculating Your Recipe

 While you can do all the calculations manually, using a lye calculator is highly recommended for accuracy, especially as your recipes become more complex.  Personally, I use a lye calculator on every recipe I try, but understanding what SAP Values are and how they impact soapmaking will help you when you want to formulate your own recipe.

I developed our recipe over years of experimenting and figuring out what to change to make my soap bars end up exactly how I like them.  I love a good hard soap bar that won't melt away, but is not drying while keeping a good lather.  

Stay tuned for some more posts on Beginner Soap Making!