What is Superfat in Soap Making and How It Affects Your Soap

Superfat in soap making is a crucial aspect that affects the final product. A small amount of excess oil, typically around 5-10%, is intentionally left in the soap formula.

This excess oil can come from various sources, such as using a higher percentage of oils in the recipe or not accurately measuring the lye. It's a delicate balance to strike, as too much superfat can cause the soap to be too soft and separate easily.

A well-balanced superfat level, on the other hand, provides several benefits, including a milder soap that's easier on skin and a more stable lather. This is especially important for soap makers who cater to sensitive skin types or those with skin conditions.

Superfatting is the process of using less lye than industry standards, resulting in leftover oil in the soap that's not bound to lye.

This leftover oil is called unsaponified fat, which provides more moisture in the soap.

Every oil requires a different amount of lye to turn it into soap, and using the exact amount can leave you with a soap that's 0% superfat.

To superfat your soap, you can either diminish the amount of lye or increase the amount of fat in your recipe.

Superfatted soap is less harsh and more moisturizing on the skin, making it a great option for people with sensitive skin.

Calculating superfat is crucial to creating a bar of soap that's both effective and gentle on the skin. To start, you need to know the SAP value of each oil in your recipe, which is the amount of lye it takes to turn 1 gram of oil into 1 gram of soap.

Each oil has its own unique SAP value, which is why you can't just substitute oils for one another without recalculating the recipe. SAP value charts are widely available online, so be sure to check those out.

Additional reading: Lye and Lard Soap Recipe

To calculate superfat, you can use the equation: (oil amount) x (SAP Value) = amount of lye needed (0% superfat). This is the starting point for your recipe.

If you want to superfat by 5%, you'll need to multiply the lye required by 0.95, which is the same as (1 - 0.05). This will give you the new lye amount for your 5% superfat recipe.

For example, if you're using 8oz of cocoa butter with a SAP value of 0.137, you would calculate the lye required as (8oz cocoa butter) x (0.137) = 1.096oz lye (0% superfat). To superfat by 5%, you would multiply this amount by 0.95, resulting in 1.04oz lye (5% superfat).

Fortunately, there are online soap calculators available that can do the math for you, making it easier to get the right amount of lye for your recipe.

Related reading: Cocoa Butter for Soap Making

Some people and/or recipes will suggest holding out your most luxurious oils or butter to add in at trace as the "superfat" oils. This is a common practice in soap making.

The superfat ratio may be different depending on the type of fat you use. For example, coconut oil soap will likely need superfat to avoid being too drying.

A too high superfat can leave the bar of soap too soft and reduce the lather, which can be a problem if you're looking for a good cleansing experience.

Some people and/or recipes will suggest holding out your most luxurious oils or butter to add in at trace as the "superfat" oils. This is especially important when working with coconut oil soap, as it can help prevent the soap from being too drying on the skin.

The superfat ratio may be different depending on the type of fat you use. For example, coconut oil soap will likely need a certain level of superfat to avoid being too harsh.

A too high superfat can leave the bar of soap too soft and reduce the lather. This can also lead to a greasy feeling on the skin.

A different take: Coconut Scented Bar Soap

Superfatting your soap can be a great way to add extra moisturizing properties, but it's not without its risks. The more "free" oil you have in your soap, the more likely you are to have spoilage.

DOS, or Dreaded Orange Spots, can ruin your soap with small orange spots where a pocket of free oil has gone bad. This is a real concern, especially if you're new to soap-making.

To avoid this issue, it's essential to use a lye calculator that can help you determine the right amount of lye to use. If not, you can simply calculate the discount by multiplying your lye amount by .95 (95 percent) to get the correct amount.

Experimenting with different superfat percentages can be a great way to find what works best for you. Try a batch at 3 percent and a batch at 10 percent to see which outcome you prefer.

For another approach, see: Orange Bar of Soap

Superfatting is a common practice in soap making that involves intentionally using more oil than necessary in a recipe to create a certain percentage of "leftover" oil after saponification.

This leftover oil adds to the moisturizing ability and emollient properties of the soap, making it a desirable trait for many soap makers. I personally prefer to superfat at 5% because it makes for a soothing bar without being too soft or inhibiting lather.

Superfatting also provides a safety margin to ensure that there is never any unreacted lye in the finished bar of soap. You can calculate superfat by using the SAP value of each oil, which is the amount of lye needed to turn 1 gram of oil into 1 gram of soap.

The SAP value is extremely important when formulating soap recipes, and it's why you can't just substitute oils for one another without recalculating the recipe. You can find SAP value charts online or use a soap calculator to make the process easier.

To superfat by 5%, you multiply the lye required by 0.95 (1 - 0.05). For example, if you're using 8oz of cocoa butter with a SAP value of 0.137, you would calculate the lye needed as follows: (8oz x 0.137) x 0.95 = 1.04oz lye.

Explore further: Bar Soap without Fragrance

Superfatting is a personal choice, and the level of superfatting you use depends on your preference. Most soapmakers use more oil than can be transformed by the lye.

The 0% superfat calculation is the precise amount of lye to use to ensure the fatty acids and lye have completely bonded and been transformed into soap.

Superfatting levels of 4%-10% are commonly used, and calculations for these levels are provided on soapmaking websites.