What is Lye in Soap? How is Lye Used for Making Soap?

By Marsha Harrison

Fact-checked by Kia Lowe

what is lye in soap

Have you ever wondered what is lye in soap? Lye is the main ingredient in many homemade soap recipes.

But before we get into the nitty-gritty details of making homemade lye soap, it’s important to understand how and why the lye chemical process works and how it became as popular as it is today.

In this post, we’ll go into detail on lye’s primary function in the saponification process, its pros and cons, and much more. So read on!

What is Lye Using in Soap?


Lye is a chemical that, when combined with water, creates sodium hydroxide and helps create soap in the saponification process.

There are several ways to create lye soap ranging from the cold process, and hot process down to the more traditional handmade soap recipe with an ash and lye mix, but the net result is the same–soap!

There are generally two types of lye used in soapmaking. It depends on your preference for how you want your soap to feel in your hands and on your body.

  • If you want a solid bar of soap that feels luxurious when bathing with it, then you’d use sodium hydroxide (caustic soda). Your lye base in combination with coconut oil or olive oil for your fats or oils during saponification.
  • If you want something more exfoliating on your skin in liquid form, then perhaps potassium hydroxide (caustic potash) would be more suitable as both produce similar results as far as pH levels

How is Lye Formed?


What would lye look like in its natural form? Lye, otherwise known as sodium hydroxide, is formed by combining water and wood ash.

Making lye is quite simple but can be dangerous if you don’t follow proper safety measures while preparing lye solution.

Method 1: Wood ash

This method is easy to follow, requiring burning wood until all that remains are ash and coals.

  • The ash must then be collected and put into a container with enough water to cover it completely.
  • Let this sit for two days, occasionally stirring so that the mixture doesn’t settle on the bottom.
  • After two days, add more water until the mixture becomes clear again; this may take up to two weeks, depending on how much lye you want to make at once.
  • The resulting substance is called lye, but it’s the potassium hydroxide type, a caustic chemical salt.

Method 2: Electrolysis

The second method involves electrolysis and is commercially produced.

  • Commercial lye is produced through electrolysis, which involves passing an electric current through water to separate out sodium (Na) and chlorine (Cl).
  • Sodium hydroxide is then produced when the product is treated with potassium carbonate to form potassium chloride.

How is Lye Used for Making Soap?


Lye is commonly used as a drain cleaner, but it’s also used in industrial processes and in making soaps and detergents.

In the world of soap making, lye ingredients serve as the foundation.

Here is a quick breakdown of what the process looks like when you want to use lye to make soap:

  • The purpose of adding lye to fats is to saponify them, which means that the molecules in the fat are broken down into smaller ones through a chemical process known as hydrolysis.
  • This reaction results in the formation of glycerol (glycerin) and fatty acids from the fat molecules in your mixture’s ingredients list.
  • The combination of these two compounds makes soap foam up when poured into the water because of their ability to lower its surface tension; this property makes it easier for dirt particles to be washed away.
  • In short, the lye solution forces the coagulation of oils without dissolving in water; this results in a hard mass we know as soap.

Is Lye in Soap Dangerous?

The short answer is that lye is considered hazardous due to its corrosive nature. Ingesting or inhaling the powder can cause burns on your skin.

It’s a common misconception that the water in soap making is what makes it safe.

The real reason that soap is safe to use on your body is because of the fatty acids that are released during saponification, which are what actually cleanses your skin, not the water.

Lye can be harmful if handled improperly. When used as directed, it is perfectly safe to use in soapmaking.

How Do You Safely Handle Lye?


Lye is safe when handled carefully. Here are some common safety tips when lye is involved:

  • If you’re making soap at home, make sure to wear protective gloves and safety goggles when handling lye, whether it’s in solid or liquid form
  • Laminate film, vinyl, or nitrile gloves offer more protection than latex gloves; however, if you’re only using small amounts of lye at a time, then latex or gloves should suffice for most people.
  • Make sure that you’re working in a well-ventilated area with good lighting — preferably outdoors — so that you can see clearly and avoid inhaling lye fumes.
  • Never add water to lye directly; always add lye to water.
  • Use a plastic funnel to pour your lye into a glass container, rather than pouring from a plastic bottle directly into the glass container. This will prevent spills and splashes from getting on your hands or clothes.
  • Lyre reacts adversely with metal and shouldn’t be used in aluminum or copper pots.
  • Avoid touching your face or eyes until you have thoroughly washed your hands with soap and water.
  • If any lye gets on your skin, wash it off immediately with soap and water. If any lye gets in your eye, flush it well with water for 15 minutes and get medical attention right after.

Where Can You Get Lye?

Lye can be purchased from most hardware stores, or online from soapmaking supply companies, or in the soap-making section of craft stores.

It comes as a granulated form or as pellets that dissolve quickly in warm water.

  • Some brands of lye are labeled as food-grade and safe for use in soap making.
  • Other brands are labeled for industrial use only, which means that they are not intended for human consumption or contact with skin or eyes. These types of lye should never be used for soap making unless you know what you are doing!

Lye comes in different grades: pure granules (very strong), technical grade (slightly weaker) and food grade (weaker still). The pure granules are best for soap making because they are purer and more concentrated than the rest.

What Are the Pros and Cons of Making Soap Without Lye?

Soap is made with a combination of fats and oils, water, and sodium hydroxide (lye).

Soap-making can be done without lye, but it’s not recommended because it’s difficult to get consistent results without using it. Technically, without lye, it’s no longer soap but detergent.

Lye also sterilizes your soap, killing bacteria and other microorganisms that could contaminate your batch of homemade soap.

If you don’t want to handle lye yourself, there is an easier alternative. However, lye is still involved but you don’t have to go through the measuring and mixing it with the essential oils.

You can use melt-and-pour bases that already contain sodium hydroxide and other ingredients required for saponification.

They also add hardness and stability to your finished product so it doesn’t melt away when exposed to heat or water. These bases come in different colors and fragrances so they’re easy to customize into unique products.


We’ve covered the basics of what is lye in soap making. You should now know where it came from, why you need it, how to use it and where to find it.

Is making lye soap something that’s worth the effort? Or will you stick to commercial soaps of both the liquid and bar varieties? Ultimately, what matters most is your own personal preference. But whatever you choose to do, we hope that this post has taught you that making soap with lye does not need to be scary if you follow safety precautions.

5/5 - (2 votes)

Recommended for you