The amount of lather your soap produces is directly related to the types and balance of oils you use in your soap recipe. Different oils give different amounts and different types of lathers. To add more of a bubbly lather to some oils that may not lather up as much, many soap makers add a bit of sugar to their soap recipe to help increase the lather. Adding sugar can help make a light, bubbly lather with large bubbles. There are three ways to augment your recipe and can add sugar to the process of soap making.
Add to the Water Before the Lye
When making your lye-water solution, add the sugar to your water before you add your lye to the water. Make sure it is completely dissolved before adding the lye. If your soap recipe calls for salt, this might be a good time to add salt to the water, too. As for the ratio of sugar-to-water, you want 1/2 to 1 teaspoon of sugar per pound (16 ounces) of oils. For example, if you are using 32 ounces of oils, then add 1 to 2 teaspoons of sugar. If you are using 48 ounces of oils, then add 1 1/2 to 3 teaspoons of sugar, and so on.
This is the easiest method, though sometimes the heat of the lye solution will begin to caramelize the sugar a bit and turn the sugar water a bit of a beige color. It will not be quite like the orange color you get with goat's milk soap, but the sugary solution turns that color for the same reason. This is just an aesthetic consideration. It does not affect the constitution of the soap at all.
Add to the Lye Solution
Take a bit (just a few ounces) of the water you have weighed to make your lye solution and add 1/2 to 1 teaspoon of sugar per pound of oils you are using to the water. Use the same ratio as the first method. Stir until it is completely dissolved. Sometimes it helps to warm the water first. Add this sugar-water solution in at trace with your other additives, but before your fragrance oil.
Add to the Soap Mixture at Trace
Make a “simple syrup” solution of water and sugar ahead of time by taking two cups of sugar and one cup of water and slowly heat it on the stove. Stir it gently until all of the sugar has dissolved. Let it cool and pour it into a bottle that you use when you are making soap. Add 1/2 to 1 teaspoon of the syrup per pound of oils you are using (same ratio as the other two methods) to your soap mixture at trace with your other additives, but before you add your fragrance oil.
Some people have noticed that adding sugar to their soap makes it heat up, and speeds the saponification process to the gel stage. The same thing happens when milk is added. The sugars in the milk are jump-starting the gel process. Just be careful if you are adding sugar and adding milk, your soap can get quite hot.