I have been asked several times if I add glycerin to my soaps. Also a common question is do I make lye soap or glycerin soap.
No, I do not add glycerin to my soaps
Yes, I use lye and it is glycerin soap.
Confused? Let me explain.
Soap is made by combining fats and oils with lye. The lye reacts with the fatty acids in the oils and fats, resulting in soap. When the chemical reaction is complete, there is no lye left; it has all been converted to soap. That reaction is called saponification. The byproduct of saponification is glycerin.
Oil & Fat + Lye = Soap + Glycerin
If it doesn’t contain lye, it’s not soap.
Modern soap makers calculate the exact amount of lye required for a given amount and type of oil or fat so that all the lye is used up in the process. Standard practice is to ‘superfat’ the soap, essentially using more oil than required to ensure no lye remains unused in the final product. The final result is soap that contains both excess oil and glycerin, ensuring that hand made soaps are luxurious and moisturizing.
What many refer to as ‘Glycerin Soap’ is transparent soap. Transparent soap is a hot process soap to which additional solvents (sugar water, alcohol and more glycerin) are added in order to render the final product transparent, but the base recipe is essentially the same. One of the reasons glycerine is added to transparent soaps is that Steric Acid is used in place of some of the hard oils. Using a fatty acid alone makes for a very hard soap and it will not have the moisturizing glycerin byproduct.
Commercial producers often remove the glycerin for use in lotions and other products, making their soaps more drying, but what better way to encourage people to purchase more products?