Lye is a very-alkaline product that is used to make soap, but it is also used in the food and cleaning industries. There are several types of lye, the most known and most commonly used being NaOH, sodium hydroxide, and KOH, potassium hydroxide. All are metal hydroxides and are very basic (alkaline), meaning they have a very high pH. That makes them very caustic, meaning they can give you a chemical burn if you touch them with unprotected skin.


Traditionally, lye was made from wood ashes! By allowing the wood ashes to seep in water, a lye-type (or at least a caustic basic) solution was formed. This lye solution is also known as potash, or “pot ash” (from soaking ashes in a pot). In fact, the name potassium comes from “pot ash” since that’s where it was first isolated.


Lye, at least the sodium hydroxide (NaOH) type, the type normally used for making bar soap, is now made by breaking down a salt water solution (NaCl and H2O) into NaOH, H2, and Cl2 with a membrane cell chloralkali process.

Making soap nowadays is much easier and much more precise. You can easily buy lye in beads or flakes. Because their purity is known, you no longer have to guess how strong your lye is and how much you will need to make soap. That allows you to make a very accurate recipe that can be repeatedly made in exactly the same way each time. You can also tailor that recipe to use more or less lye depending on how cleansing or how conditioning you want your soap to be. I’ll go into that in more detail some other day, but that’s in reference to “superfatting” a soap or not (using more oil than the amount needed for reacting precisely with the lye to make soap).



The answer to this question really depends on your definition of soap. MY ANSWER TO YOU IN “NO”!

What most of us know as real, pure, natural soap, though, can NOT be made without lye!

Some people will argue that they’ve seen soaps without lye in the ingredients, but all of the cases that I have seen are due to one of two scenarios…

Detergent bars (Syndet Bars) of “Soap”

There are many types of bar “soap” on the market that aren’t actually really soap.

While that may sound crazy at first, perhaps some of you will remember some retro Dove commercials where they boasted that Dove wasn’t really soap, but was instead much, much better than soap because it’s less drying.

Here’s one of those fun blasts from the past…

The case of Dove is a bit unusual, though, and I’ll get to that in a minute.

That said, there are many types of solid cleansing products that are sold in bars, like soap, and that are not made with lye. These bars of “soap” are commonly referred to as Syndet bars, which comes from “synthetic detergent” bars. These detergent-based bars are made from a variety of surfactants and not from the chemical process of reacting lye with fat. There are some more natural surfactants, so that doesn’t necessarily make them bad, but it’s important to make the distinction.

I can get into a discussion about which is best some other day, but for now, let’s stick to the facts and just say that syndet bars aren’t really “soap” even though they are often referred to as such. Their pH is generally lower than soap, which may be great for many people, but that doesn’t necessarily make them best for everybody.

Melt and Pour Soap

Sometimes, people will use melt-and-pour soaps to avoid using something with lye in it.

If you are choosing to use a melt-and-pour soap because you, yourself, are afraid of handling the lye yourself, then go for it! I understand people being afraid of handling lye when they’ve never done it before.

If, on the other hand, you are choosing to use a melt-and-pour soap to avoid making something with “lye in it,” then know that your melt-and-soap bar falls into one of the two categories I was talking about above.

Either you are buying a product in which the lye was already reacted with fats to make a soap-based product, or you are using a syndet bar which isn’t really soap. (Or, you are using a mixed product that falls into both of those categories like the Dove bar.)

I don’t think I’ve ever used a melt-and-pour soap myself, but I do get the attraction of wanting something that is very simple to make. (It’s kind of like making a cake from a box mix. You can use it as is, or add things to it to make it your own.) It’s also probably the best way to make a fun project with young kids.

Use a melt-and-pour soap for one of those reasons, though, and not because you want to make soap without lye. Most melt-and-pour soaps will have other chemicals added to the soap (if they are, indeed, soap) to make them meltable (one example being propylene glycol). Natural soaps don’t normally melt into a nice, smooth thick liquid on their own. (Yes, you can melt most soaps down to rebatch them, but they normally turn into a more “rustic” looking soap that isn’t super smooth like m&p soaps are.)

So, in your quest to avoid lye, you may be using something with more questionable ingredients than pure soap.

Does soap have lye in it?

Not really!

Wait a second… I thought you just said that you needed lye to make real soap!

While you do need lye to make soap, no lye is left in the finished product. (When done correctly, of course.)

Making soap isn’t like baking a cake.

While you are using a recipe, and mixing oils with other ingredients, and mixing them with a blender, and often times pouring them into loaf pans and such, we’re really doing more of a science experiment and making a chemical reaction.

OK, I guess in the process of baking a cake, you are probably doing all sorts of chemical reactions too, but I want you to think of this in a slightly different way…

In the case of baking a cake, you think…

“I’m intolerant to dairy, so I better not put milk in my cake.” or

“I have issues with gluten, so I’d better not use wheat flour.”

In the case of making soap, it’s not quite so simple…

Soap as a Type of Salt

When making soap, you are making a type of salt, a sodium salt of fatty acids. While it’s not like the salt that we use for cooking, that more-familiar type of salt will help us better understand what we are working with anyway.

Table salt is also known as NaCl or sodium chloride. Most people don’t think of salt as being toxic, and they see it as something that is quite natural, right?

But, you wouldn’t want to eat sodium, would you? Or Chloride?

Both sodium and chlorine are quite reactive on their own, and we wouldn’t really want to be handling either one of them, at least not without being very careful. Yet, we all take in some NaCl on a regular basis. In making salt, the reactivity of each element is neutralized, and you end up with a safe product that behaves nothing like its components.

Making soap is very similar. Lye is used to make soap, but your final product doesn’t behave like lye at all. (You also won’t normally see lye listed as one of the ingredients in soap, just as you’ll see “salt” in a food’s ingredient list rather than sodium and chloride.)


That's it folks. LYE is used to make a true bar of soap but the end result has no lye in the finished product!