What is superfatting?

No, it’s not the latest diet craze. It’s a technique that people use who make handmade soap to ensure that there soaps are not overly harsh and have extra oils in the soap to help the skin.

When you calculate a recipe for handmade soap (I use the cold process method, but that’s another blog) you have to figure out the saponification value for each oil or fat you use. The saponification (or SAP) value is how much sodium hydroxide (or lye) it takes to turn one ounce of an oil into soap. Once you know the SAP value for each oil in your recipe you calculate the amount of lye you will need. But that can raise a problem: how do you know that the SAP value is exactly right for your oil. Answer: you don’t. SAP values are general values for a type of oil or fat used in a soap. There is no guarantee that your oil and the SAP value for it are a perfect match. So to get around this problem we superfat.

When you superfat you add an extra % of oil/fat to your soap to help neutralize any extra lye that might not have been used up by the oils that you calculated for. A range of 4-6% is considered normal for superfating. These extra oils help to ensure that the bar is not overly harsh and actually help make a gentler bar of soap.

Many soap makers actually rely on superfatting to create a more conditioning bar of soap, which is fine, but you also have to be careful. Add too much extra oil or fat and your bar can go rancid or be overly soft and hard to use. It’s a fine balancing act to find the perfect superfat % for each recipe.

Hope that helps. Let me know if you have any questions about superfatting.

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