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Soapmaking 101

Lesson 4: Soap Recipes

Using a lye calculator

What is a lye calculator?

A lye calculator allows you to develop and test your own recipes by telling you how much lye to use with the oils you have selected. You can also use a lye calculator to doublecheck a recipe you have selected from a book or the web before using it.

Why is it necessary?

Different oils have different amounts of fatty acids and unsaponifiable material. That means that different amounts of lye are required to produce saponification. The lye calculator will allow you to determine the correct amount of lye for your recipe.

How do I use the lye calculator?

Write out a list of oils you intend to use in your soap and the amounts (in ounces) you intend to use (Step 1 in the example below). Now multiply the number of ounces being used by the sap value of the oil (see Step 2). Total your list of figures to get the total amount of lye necessary to saponify your soap (Step 3). However, most soapmakers prefer to automatically superfat their soap by 5%. This is done by reducing the lye by 5% - also called discounting the lye (Step 4). Now calculate the amount of water needed for the recipe by dividing the total ounces of oils used by 3 (Step 5).

Example

Here is an example of the lye calculator in action with my super duper moisturizing bar for very dry skin. Feel free to use this recipe, for personal use.

Step I Castor Oil 2 oz
Cocoa Butter 2 oz
Coconut Oil 4 oz
Olive Oil 6 oz
Palm Oil 6 oz
Avocado Oil 3 oz
Apricot Kernel Oil 2 oz

Step 2 Castor Oil 2 x .1286 = .2572
Cocoa Butter 2 x .137 = .274
Coconut Oil 4 x .190 = .76
Olive Oil 6 x .134 = .804
Palm Oil 6 x .141 = 0.846
Avocado Oil 3 x .133 = .399
Apricot Kernel Oil 2 x .135 = .27

Step 3 3.6 ounces lye necessary to saponify the soap.

Step 4 3.6 x .95 = 3.4 ounces lye

Step 5 25 ounces oil divided by 3 = 8.3 ounces water.

Things to remember: