Have you ever picked up a bar of handmade soap and wondered about the ingredients, especially when you see “lye” listed? It’s a common question, and often sparks concerns: “Is there lye in your soap?” (yes, and also no), “Can you make soap without lye?” (definitely not real soap), and “Is lye soap bad for my skin?” (it really depends!). Let’s dive into the science behind soap making and clear up the confusion surrounding lye.
First, let’s address the different names you might see for lye on an ingredient label. We often use the term “lye” because it’s straightforward and most people have heard of it. However, “lye” is also known as sodium hydroxide (NaOH), its chemical name. For liquid soaps, potassium hydroxide is used instead. While “sodium hydroxide” is more chemically precise, it can sound intimidating and overly “chemical” to some. People might mistakenly categorize it as something to avoid without understanding its role.
Another term you might encounter is “wood ash extract.” This is essentially lye derived from wood ash, but the term can feel like a way to sidestep consumer unease with “chemicals” by using a more “natural” sounding name. Regardless of the name – lye, sodium hydroxide, or wood ash extract – they all refer to the same crucial ingredient when making bar soap.
Pile of sodium hydroxide flakes
So, how can soap both contain lye and not contain lye? This is where the magic of chemistry comes in. Soap making is a chemical reaction, much like baking a cake. You can’t “unbake” a cake, and similarly, you cannot “unmake” a bar of soap back into its original components. Once the chemical transformation occurs, the initial ingredients are changed forever.
While a cake baked with eggs still contains eggs in a changed form, soap is different. Soap batter starts with lye, fats or oils, and water. But in properly made soap, no lye remains in the final product.
This transformation happens through a process called saponification. When sodium hydroxide (lye), fats, and water are mixed, a chemical reaction takes place. The bonds within the molecules break and reform. Specifically, the sodium hydroxide molecules are completely used up as they react with the fatty acids in the oils. Think of it as neutralization: lye, a strong base, is neutralized by the fatty acids.
Consider our Simple Tallow Soap. It’s crafted with just three ingredients: tallow (animal fat), sodium hydroxide, and water. When these are combined, they react, transforming into a new compound called sodium tallowate. Chemists classify this as a sodium salt of fatty acids – which is soap!
The original sodium hydroxide is entirely consumed in this reaction. Therefore, when you see ingredients like “sodium palmate,” “sodium cocoate,” “sodium lardate,” or “sodium tallowate” on commercial soap labels, these are not the ingredients that went into the soap. Instead, they are the names of the soap itself – the result of the saponification process. It’s listing what is produced, not what was used to make it.
Therefore, do our soaps contain lye? No, the finished soap does not contain lye. But is lye used in the soap making process? Absolutely, it’s essential.
Can you make soap without lye?
The answer to this is straightforward: no. You cannot create true soap without lye (either sodium hydroxide for bar soap or potassium hydroxide for liquid soap). There are products marketed as “soap” that bypass lye, but these are typically detergents, not soap in the traditional chemical sense.
The soap making method we use is called cold process (CP) soap making, a method of creating soap from scratch using lye and oils. There’s also melt and pour soap base. This is pre-made soap that has already undergone saponification by the manufacturer. It contains added ingredients that allow it to melt smoothly, making it easy for crafting, but the crucial step of using lye has already been completed.
Many liquid body washes and cleaning products, including most laundry “soaps,” are actually detergents. Detergents rely on a different chemical process than saponification to get things clean. While effective, their ingredient lists are often longer and their production processes are more complex compared to traditional soap.
Is lye soap bad for your skin?
Most of our soaps are specifically formulated to be gentle and safe for skin. The exception is our Household Tallow Soap. This soap is designed for cleaning dishes, surfaces, and laundry stains, not for skin. Its recipe is intentionally formulated to have no excess fat left over for moisturizing (unlike our skin soaps, which include extra fat, known as “superfatting,” to prevent dryness). Using Household Tallow Soap on your skin would likely be very drying and potentially irritating.
For properly made soap intended for skin use, the saponification process ensures that there is no lye remaining in the final bar. The result is a gentle cleanser, often enriched with natural glycerin (a byproduct of saponification), which is moisturizing for the skin.
If you’ve read this far, thank you for your curiosity! The science behind everyday items like soap is fascinating, and understanding the role of lye helps to demystify soap making and appreciate the chemistry in our daily lives.
