Lye in Soap Making


sodium hydroxide

Ever since I started making soap, I’ve gotten a lot of questions about lye. What exactly is it? Is it safe to use? Can you make soap without it? Are “all natural” soaps made with lye?

These are great questions and I had many of them myself when I was first getting started with soap making.

The short answer is yes, all soap is made with lye, even “all natural” soaps. If it’s not made with lye, then it’s not soap.

You might be checking out products in the cosmetic aisle of your local store and notice that some commercial soaps don’t have lye listed on the ingredient label. Lye can go by two different names: sodium hydroxide (solid soap) or potassium hydroxide (liquid soap).

Lye could also be hiding under a number of other names like sodium palmate (sodium hydroxide and palm oil), sodium cocoate (sodium hydroxide and coconut oil), and the list goes on for all different oils. These names indicate that the oil has been mixed with and reacted with the sodium hydroxide.

Last, it could also be listed under the blanket term “saponified oils” which again, indicates that the oils in the soap were mixed with sodium hydroxide.

There is also a possibility that the “soap” you’re looking at in the store wasn't made with lye because isn’t soap at all, but rather it’s a “chemical detergent”.

So now that we’ve established that lye is necessary for making soap, you might still be wondering…but isn’t lye caustic…I mean it’s used in drain cleaners, right?

Lye on its own is a caustic chemical, which is why soapers are extremely careful when working with it. It’s important to where long sleeves, pants, closed toed shoes, gloves, and eye protection. Alway soap in a well ventilated area or where a mask to avoid inhaling fumes.

Okay, so then how is it safe to use soap on your skin?

To answer this, you need to know the chemical reaction that takes place in the soap making process, also known as saponification.

Soap is made by mixing oils or fat with lye in liquid. Oils are made up of fatty acids and lye is a strong base. When these are balanced correctly the reaction results in an entirely new substance: soap and glycerine.

That’s why soap is perfectly safe to use on your skin, because there isn’t actually any lye in the final product.

Beginner soap makers: if you’re still a little apprehensive about handling lye, consider using a melt and pour base. These are pre-made bases that you can buy in which the saponification process has already taken place. All you need to do is heat up the base to melt it, then you can add your design and fragrance, then pour into a mold and let cool. No lye needed.