Lye Then & Now - A Look at Traditional vs. Modern Soap-Making

Our 2024 Tallow Soap & Balm Wrapped showed us that " What is lye, and why is it used in soap?" is our most-read blog post, which means people are curious about this essential ingredient. So, we decided to dive even deeper into the history of lye—where it comes from, how it was traditionally made, and how today’s soap makers, including us, use precise measurements for consistency. 

Lye is the renowned ingredient that turns fats, such as beef tallow, into soap, making it an essential part of traditional and modern soap-making. While today, we rely on carefully measured lye for high-quality soaps, the process wasn’t always this predictable. Historically, people extracted lye from wood ash, a method that required skill, patience, and a bit of luck. Let’s explore how lye has evolved—from its rustic, unpredictable beginnings to the reliable ingredient we use today. 

The Origins of Lye

Before commercial lye became available, early soap makers had to create their own alkaline solution. Typically, that meant leaching lye from wood, a technique practiced for centuries across various cultures.  

How Traditional Lye Was Made:

1. Burning hardwood – Soap makers would burn hardwood (like oak or hickory) to produce white ash. Softwoods like pine were avoided because their lower potassium content created a weaker lye. 

2. Collecting the ash – Once cooled, the ash was gathered and placed into a barrel, hollowed-out log, or an ash hopper (a funnel-shaped container). 

3. Leaching with water – Rainwater or soft water was poured over the ash, and as it trickled through, it extracted potassium hydroxide (a form of lye). 

4.  Testing for strength – Since there were no precise measuring tools, soap makers used homemade tests: 

   • A raw egg or potato was dropped into the lye water. If it floated to the proper height, the lye was strong enough for soap. 

   • If it sank, the solution was too weak and needed more leaching time. 

   • If it floated too high, it was too strong and needed dilution. 

This traditional method worked, but it had one major drawback: inconsistency. The strength of lye varied from batch to batch, leading to soap that was too soft, too harsh, or unpredictable in quality.  

The Evolution of Modern Lye

As chemistry advanced, sodium hydroxide (NaOH) became the standard for soap-making. Unlike traditional wood ash lye, which is potassium hydroxide (KOH) and produces softer soap, modern sodium hydroxide creates firm, long-lasting soaps. 

How Modern Lye is Made:

Industrial electrolysis – Today, lye is produced by running an electric current through salt water, separating the sodium, chlorine, and hydroxide ions to create pure sodium hydroxide. 

Measured precisely – Unlike wood ash lye, modern lye comes in precise, measured flakes, beads, or powder ensuring every batch of soap is consistent. 

Controlled pH – Today, we can calculate exactly how much lye is needed for a given amount of oils, preventing harsh soap that could irritate the skin.   

Why modern soap-making is more Reliable 

Today’s soap makers benefit from: 

Predictability – No more guessing if the lye is too strong or weak. Precise measurements create a balanced soap every time. 

Safety – Traditional lye-making involved caustic, unpredictable solutions. Modern lye is safer to handle when used properly. 

Customization – By calculating the right lye-to-oil ratio, soap makers can create moisturizing, gentle formulas with extra nourishing properties. 

Traditional vs. Modern Soap: What’s the Difference?

Combining both for ideal results

While modern lye offers precision and convenience, traditional soap-making methods remind us how resourceful early artisans were in creating a necessary household staple. Handmade, tallow-based soaps still honor this history—using natural ingredients and time-honored techniques—but with the benefit of reliable measurements for safety and consistency. 

If you’re a natural soap lover, understanding what goes into your soap helps you make an informed decision about the products you use on your skin. Knowing that real soap requires lye—whether sourced from wood ash or modern sodium hydroxide—allows you to choose authentic, nourishing soaps over synthetic options. The next time you pick up one of our soaps, we hope you’ll appreciate the ingredients and centuries of craftsmanship behind them.

Frequently Asked Questions about Lye

We have discussed this in previous blogs, but if you’re familiar with soapmaking, you know lye is an essential ingredient. Lye, also known as sodium hydroxide, is a strong alkaline substance that helps create the chemical reaction necessary for saponification, the process that turns oils and fats into soap. Despite its popularity in soap making, lye can be intimidating for beginners and may raise some questions. In this blog, we’ll cover frequently asked questions about lye and why it’s safe and beneficial to use in soaps.

What is lye, and how is it used in soap making?

As we mentioned, lye is a strong alkaline substance used in soapmaking to create the chemical reaction necessary for saponification. When lye is mixed with water and oils/fats, lye causes a chemical reaction called saponification, which makes soap. During this reaction, lye breaks down the oils and fats into their component parts, which then react with the lye to create soap.

Is lye dangerous?

Lye is a caustic substance and can be dangerous if not handled properly. When working with lye, wearing protective gear such as gloves, goggles, and a mask to avoid direct contact with the skin or eyes is essential. Always keep lye out of reach of children and pets, and avoid inhaling fumes when working with it. However, when used correctly, lye is safe to use in soap making.

Soaps made with lye are safe to use on the skin once they have been properly cured. During the soapmaking process, all of the lye is used up, ensuring no leftover chemicals or harmful substances are in the finished product.

Is there a substitute for lye in soap making?

There are alternatives to lye in soap making, such as melt-and-pour soap bases, but they don’t offer the same level of customization and control as using lye to create soap from scratch. When making soap from scratch, lye is necessary to complete the chemical reaction that turns oils and fats into soap.

Is lye used in other types of products?

Yes, lye is used in many other products besides soaps. It is used in the production of paper, textiles, and detergents. It is also used in the food industry to make olives, cocoa, and pretzels. In addition, lye is used in biodiesel manufacturing, as a pH regulator in water treatment plants, and as a cleaning agent for household drains and ovens. While lye can be dangerous if not handled properly, it is vital in many industries and products.

Why is lye great to use in soaps?

Lye is great to use in soaps because it’s a powerful and effective ingredient that creates a chemical reaction necessary for saponification. It allows soap makers to customize their recipes and create unique blends of oils and fats to make a soap that meets their specific needs. Lye also helps create a hard and long-lasting bar of soap, making it a cost-effective ingredient in soap making.

We use lye in our soaps because it is necessary for saponification, but it also helps create hard, long-lasting bars of soap. Using lye in our soaps gives us the flexibility to make our soaps custom to fit our needs. That means using our choice of all-natural, grass-fed, or finished tallow and olive oil to make high-quality bars of tallow soap. While lye can be intimidating for beginners, with proper safety precautions, it is safe to use and is an essential ingredient in creating high-quality, handmade soap.

What is lye, and why is it used in soap?

You may have heard that lye is used in soap to create a soft, smooth, and natural bar of soap. However, you might wonder how it works and why we use it in our soaps. In this blog post, we'll answer those questions so you can learn more about the ingredients found in your favorite product. Even if you're unfamiliar with lye, there is a very high chance you've used it in soap at one point or another without realizing it. All natural soap is made with lye. It is the most traditional and natural way to make soap.

What is lye?

Lye is a very-alkaline product that has been used to make soap for decades. It also has uses in other industries, such as food and cleaning. Lye is a general term for two different alkaline compounds known as Sodium Hydroxide (NaOH) and Potassium Hydroxide (KOH). They are both metal hydroxides and basic alkaline, so they have a very high pH. The high pH makes this mixture very caustic, which means that if you don't protect your skin when you touch it at this stage, it can cause a chemical burn. These two compounds are highly water-soluble and are sometimes referred to as caustic soda.

Though this may sound odd to put in soap, the chemical reactions that occur later in the soapmaking process, called saponification, neutralize the lye in the soap while activating its cleaning power.

How is lye produced?

The traditional way of making lye was by allowing wood ashes to seep into the water, resulting in a lye solution. This process is also known as "potash," which comes from the method of soaking ashes in a pot. Modern lye, which is normally used for making bar soap, is now made by breaking down a saltwater solution with the chemicals we mentioned above. Salt is an alkaline earth metal, and water is neutral; the reaction between these two creates lyes that vary widely depending on what kind you use: baking soda produces up to 7% NaOH while Epsom salts cause only 10%.

How long has lye been used?

Lye has been used for thousands of years to make many important products like soap, food, and paper. It's also a key ingredient in producing many other things, such as glass cleaner and fertilizer. 

You can't make real soap without lye. All natural soaps have lye as an ingredient in them; synthetic chemicals can now be used instead of lye (like phthalate-free glycerin), but we wouldn't consider that natural soap because it contains no botanical ingredients or essential oils from plants or flowers.

How is lye added to soaps?

The process typically involves mixing lye with oils or butters, which contribute to the soap's scents and other natural properties, such as vitamins and minerals.

After we ground, render, and filter our suet (beef fat), we add lye to our completed tallow product. The reaction between oil and lye leaves no residue in the finished product. At the end of the soapmaking process, there's no lye left in your soap—it forms a bond with oil and becomes soap!

Is soap made with lye safe to use on the skin?

Yes, soaps made with lye are safe to use on the skin once they have been properly cured. During saponification, the reaction between the fats and lye produces a product that is safe for use on the skin after all curing has been completed. During the soapmaking process, all of the lye is used up, making sure that there are no leftover chemicals or harmful substances in your finished product!

Why do we use lye in our soaps?

There are a few reasons we use lye in our soap:

1. It's the most natural way to make soap, allowing us to stick with the most traditional methods possible.

2. Using lye avoids the use of unnecessary synthetic chemicals larger companies may use that can cause skin irritation or allergies.

3. Because lye creates soap with powerful natural cleansing properties, it makes for an amazing bar of handmade soap!

Finally, since handcrafted artisans traditionally use lye throughout history, it makes sense that we would choose this method as well when making our own handmade products."

So, why do we use lye in soap? Well, it's actually a great question! Lye comes from natural sources like clay and limestone. It is 100% pure sodium hydroxide, which can make all sorts of things like detergent, laundry detergent, or deodorant products. The main reason soapmakers use lye in their soaps is that it has many benefits over other ingredients, such as salt or synthetic chemicals found in many non-natural soaps today.