Cold Process Soapmaking A Simple Guide to Superfat
Soapmaking blends precise science with creative art. Each oil has a unique saponification value, which tells you how much lye is needed to convert one gram of oil into soap.
When making cold process soap, you use a simple formula:
(oil amount) × (SAP value) = required lye amount
For example, using 10 ounces of olive oil with a SAP value of 0.134, you calculate:
10 oz. × 0.134 = 1.34 oz. of lye
This means you need 1.34 ounces of lye to turn 10 ounces of olive oil into soap.
If you use exactly the calculated lye, your soap has a 0% superfat (no extra oils left over). Many soapmakers prefer a bit of extra oil—called superfat—to ensure a gentler, more moisturizing bar. Superfat levels can range from 1% to 20%.
There are a couple of ways to calculate superfat:
Using a Lye Calculator: Enter your recipe and choose the desired superfat percentage, and the calculator adjusts the lye amount for you.
Manual Calculation: Multiply the required lye by (1 – desired superfat percentage).
For instance, for a 4% superfat: 1.34 oz. × (1 – 0.04) = 1.29 oz. of lye
A handy rule of thumb is that for a one-pound batch, a 5% superfat roughly means adding about 0.8 oz. of extra oils.
We usually opt for a 5% superfat because it makes the soap more luxurious without compromising its firmness or lather. However, superfatting is a personal choice. Some soapmakers go as high as 15%, and for harsher oils like coconut oil, a 20% superfat can make the soap gentler on the skin. Experimenting with different levels is the best way to find your perfect balance.
Superfatting FAQs and Troubleshooting
What is Superfatting?
Superfatting refers to the practice of intentionally leaving extra oils in your soap so that not all the fats are converted to soap. This extra oil helps to moisturize the skin and can create a gentler, more conditioning bar.
How Much Superfat Should I Use?
While many soap makers opt for a superfat level between 5% to 8%, the ideal percentage can vary depending on your oils, fragrances, and desired soap characteristics. Experimenting with small test batches can help you determine what works best for your recipes.
Why Does My Soap Feel Greasy or Soft?
Too high a superfat level can sometimes lead to a soap that feels overly oily or softer than expected. Consider adjusting your superfat percentage or choosing harder oils to balance the formulation. Additionally, ensuring thorough mixing during the trace stage is crucial for an even distribution of fats.
How Can I Customize Superfatting for Different Skin Types?
For drier or more sensitive skin, a slightly higher superfat may provide extra moisture and gentleness. Conversely, if you’re targeting a firmer bar or a soap with a stronger lather, you might opt for a lower superfat level or experiment with different oil combinations.
Tips for Troubleshooting Superfat Issues:
Mix Thoroughly: Ensure that all the oils are fully incorporated during the mixing process so that the superfat is evenly distributed throughout the batter.
Test Small Batches: If you’re new to superfatting or trying a new oil, start with a small batch to observe how the extra oils behave.
Adjust Oil Types: Some oils have unique properties. For example, coconut oil can create a harder bar with a good lather, while olive oil contributes to a creamier feel. Balancing these can help you achieve the desired result.