What Is Lye: Everything You Need To Know

by Erin Sweeney September 10, 2020

What Is Lye: Everything You Need To Know

This content was updated for accuracy and relevance on November 3rd, 2020

Here at Edens Garden, we were more than excited to enter the magnificent world of Natural Bar Soap made with essential oil. For something that seems so simple, bar soap making is actually full of complexities, and there is a lot of misinformation out there. 

A question we hear fairly often is if we use lye to make our cold process soap. The answer is— Yes!

Lye has a reputation for being dangerous. However, once it undergoes a chemical reaction to become soap, it’s completely safe. Whether you’re curious about how we use lye in our soap recipe or you’re interested in making homemade lye soap, we’re here to help answer all of your questions about the history of soap making with lye and different lye soap uses.

Let’s get started!

What Is Lye Made Of?

Lye is a highly alkaline chemical solution. The most common is sodium hydroxide, NaOH, but lye can also refer to potassium hydroxide, KOH. 

As an alkali, lye solution is highly basic. If you remember your high school chemistry days, pH exists on a scale from 0 to 14. Acids are at the lower of the spectrum, while bases, also known as alkaline substances, are at the higher end.

  • Lemon juice has a pH of 2

  • Water has a pH of 7 (neutral)

  • Lye has a pH of 13

Both strong acids and strong bases are caustic and can damage human skin, which is why lye has a reputation for being dangerous. If lye comes in contact with your skin, it begins to react with surface oils—a painful prospect!

However, that only applies to liquid lye, the pure chemical solution. Now, it’s easy to purchase lye beads or flakes that are not nearly as dangerous to work with (although you still need to exercise caution). This is also called “melt and pour” soap.

What is lye used for? This chemical is essential to a variety of industrial purposes, the most famous of which is making homemade soap. Others include:

  • Surface disinfectant

  • Curing food

  • Manufacturing processes

How Is Lye Made?

Back in the day, our ancestors made old fashioned lye soap by boiling wood ash. Then, lye was skimmed off the top. In addition, some ancient soap makers made an alkali from sodium bicarbonate (baking soda) and calcium oxide. 

Both of these methods yielded inconsistent lye that made it more difficult to measure its potency and accurately calculate the amount of fat that had to be added to make safe soap.

Nowadays, lye is made from ordinary salt.

The soap making process works as follows:

  • Salt (NaCl) is dissolved into water. Salt crystals fall to the bottom of the container.

  • Graphite rods are inserted into the mixture. 

  • Electricity is then run through the rods. Attracted by the charge, crystals of lye attach themselves to the rods. 

  • After that, the liquid is poured off and allowed to evaporate until nothing but lye crystals remain.

Then, this lye can be used for a variety of purposes, including making soap batter.

How Soap Is Made

What is lye soap? The short answer is that all soap is lye soap. 

True soap bars cannot exist without lye. In order to better understand lye, let’s first discuss the question "How does lye work in soap?"

Bar soap is made through a chemical process known as saponification (sapo is Latin for soap): 

  • A lye solution is combined with oil or fat to cause a chemical reaction. 

  • This reaction breaks down the fats or oils into fatty acid chains and the lye mixture is neutralized in the process.

Lye can react with oils and fats in a heated environment or a cold environment.

Through a hot process method, soaps can go from liquid form to a solid bar form in minutes. When an outside source of heat is applied to a lye and oil solution, the water molecules in the oil evaporate and the saponification process is sped up. 

Although hot processing lye is much quicker, we chose to cold-process our bar soaps. Heat can change the chemical characteristics of essential oils and we want to deliver their best, most potent effects in our natural soap. One of our favorite natural bar soaps is Fighting Five, which is packed with immune-boosting properties to help eliminate germs without drying out your skin.

Without lye in soap making, there would only be puddles of fat and oil. In fact, if a soap bar is not made primarily of cleansing alkalized oils, the FDA does not consider it a soap at all!

Why Do You Need Lye For Soap Making? 

What is soap without lye? Why, it’s not soap at all! Syndets (synthetic detergents), which are the most common forms of cleansers on the market, are surfactants bound together in a bar to cleanse and lather. 

While some claim to be lye free soap, lye is often hiding under the name of another ingredient. Many soaps claiming they are made without lye actually did use it at some point in the manufacturing process. Common ingredients that were made using lye include the following:

  • Sodium tallowate produced by a reaction between lye and animal fat

  • Sodium cocoate – produced by a reaction between lye and coconut oil

  • Sodium palm kernelate  produced by a reaction between lye and palm oil

In each of these cases, sodium reveals the fact that these oils and fats had previously reacted with lye.

Even melt-and-pour soaps contain ingredients that were derived from a reaction with lye.

Lye In An Ingredients List

True soap falls under the jurisdiction of the Consumer Product Safety Commission (CPSC) and does not require an ingredients label. 

However, if there is a label, there are two main ways to list soap ingredients:

  1. Some manufacturers list the raw ingredients put in the soap base, including the lye. 

  2. Others list the compounds in the final soap bar—what’s left after all chemical reactions have occurred.

Our soap follows the latter method. When a vegetable oil reacts with lye, it becomes a saponified version of itself. Coconut oil goes in and saponified coconut oil comes out. This term refers to coconut oil that has been made into soap.

Is Lye Safe, Or Is Lye Dangerous?

Lye, by itself, is extremely caustic. However, soap with lye should be completely safe—assuming it’s been made properly. Lye soap that is improperly made or aged can have too much or insufficiently mixed lye and remain corrosive. 

It is for this reason that we “superfat” our soaps by adding more vegetable oils than required to dissolve the lye crystals. We also cure the soap bars for 4-6 weeks to ensure they are not only safe but also highly moisturizing and cleansing!

When it comes to soap, lye is your friend. Through the magic of chemistry, the vegetable oils in our bar soap produce a chemical reaction with lye that leads to the creation of a glycerin-rich soap bar that nourishes your skin. 


  1. “Sodium Hydroxide.” Chemical Safety Facts. https://www.chemicalsafetyfacts.org/sodium-hydroxide/ 
  2. “Frequently Asked Questions on Soap.” FDA. https://www.fda.gov/cosmetics/cosmetic-products/frequently-asked-questions-soap

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Lynne Howell

October 6, 2021 at 1:53 pm

What happens to soap if you put essential oils in Your oil mix before you put the lye water.

Edens Garden

July 26, 2021 at 11:41 am

Hi Tanya! We suggest checking with the manufacturer you purchased the lye from.


July 26, 2021 at 10:56 am

I have 50 lbs of lye that had gotten hard..
Is it still usable in soap