Let’s Talk About Soap!

What actually is soap?

Not just the bar in your shower—but what it’s doing when you use it. Why does it need to lather? Why do some products say “body bar” instead of soap? Is body wash actually soap? And what’s going on with that foam in public bathrooms?

Soap seems simple. It’s anything but.

In this blog post, we’re going to break down what makes soap soap, how it actually works, and why some products that look like soap… technically aren’t.

True Soap

Let’s start with true soap. “True soap” is an FDA defined category. For soap to be “true soap” it must fulfill these requirements: 

• a majority of the composition of the soap must be alkali salts of fatty acids, which is essentially science jargon for the byproduct of fats/oils with an alkali, such as sodium hydroxide, or potassium hydroxide. 

• The only thing in the soap that is producing the cleansing effect must be the alkali salts of fatty acids

• To qualify as ‘true soap,’ its primary purpose must be cleansing, and it can’t make cosmetic or drug claims.

That last part is one of the most important. That is what separates body bars, from “true soaps”. Body bars, and soaps that the FDA considers “cosmetic” do not strictly cleanse. They are “articles intended to be rubbed, poured, sprinkled, or sprayed on, introduced into, or otherwise applied to the human body...for cleansing, beautifying, promoting attractiveness, or altering the appearance" [FD&C Act, sec. 201(i)]. “Soap” has largely become an umbrella term for any cleansing bar, even though there’s real differences.

Syndets

Now syndets, or synthetic detergents, fall into the same category, but they are very different. 

These are “soap” bars, or body washes made with synthetic surfactants, humectants, fatty acids, and other chemicals to cleanse, and moisturize the body. 

Now, I don’t need Big Detergent coming after me, so let me say there is nothing inherently dangerous with synthetic detergents, moisturizers or the like. But the composition is different, and it’s worth noting. That’s what this blog does. 

Some bars on the market—even from brands known for syndets—combine synthetic surfactants with traditional soap ingredients like sodium tallowate (a soap derived from animal fats). These are often referred to as hybrid bars.

Where We Fit

Our bars are made the traditional way—oils and lye, combined through saponification. Structurally, that is true soap. But because they’re designed to do more than just cleanse, they’re technically classified as cosmetic body bars.

So while the method is traditional, the intention goes beyond it.

So What’s Happening Inside Those Suds: 

Let’s introduce some of the major players and their roles in those beautiful blocks of soap, or gorgeous bottles of body wash in the shower.

Surfactants: 

Surfactants are molecules found in both “traditionally made soaps” as well as syndets. These surfactants form micelles, which are tiny spherical structures that essentially pick up grease, dirt and other grime, help emulsify it into the liquid, i.e. water, and get it down the drain. In traditional soap, the soap itself acts as a surfactant, while in syndets a common additive is sodium lauryl sulfate.

Humectants and Emollients:

Humectants are molecules that help keep the skin hydrated by attracting and holding onto water. Common humectants you might see include glycerin, sorbitol, propylene glycol, and hyaluronic acid. Glycerin is a natural byproduct of saponification, so many artisan bars will contain glycerin. Emollients are different from humectants, but they’re still moisturizing in nature. Instead of pulling water into the skin, emollients work by softening and smoothing the skin’s surface. In traditional soap, this effect comes from the fats themselves. Leftover oils act as emollients, helping the skin feel softer and less stripped after washing. In syndets, emollients are added more deliberately, using ingredients like lanolin, fatty alcohols, or silicones to control how the product feels on the skin.

Fatty Acids:

This is where it all starts to come together. When oils react with lye during saponification, they don’t stay as oils—they transform into the alkali salts of fatty acids, which is what actually is soap. In synthetic detergents, fatty acids are often added to shape the bar—affecting hardness, lather, and overall feel. When companies select specific components—whether in synthetic detergents or traditional soap—they’re shaping a specific experience.

Here are some of the most important ones:

Oleic Acid:

Found in high amounts in oils like olive oil, oleic acid contributes to a milder, more conditioning bar. Soaps high in oleic acid tend to produce a low, creamy lather and are less likely to strip the skin. This is why olive oil soaps (like Castile) are known for being gentle, even if they don’t bubble as much.

Lauric Acid:

Lauric acid, found in oils like coconut oil, is almost the opposite. It creates a highly cleansing soap with big, bubbly lather. That satisfying foam you get from many soaps largely comes from lauric acid. The tradeoff is that too much can feel drying or stripping, which is why it’s usually balanced with other fatty acids.

Stearic Acid: 

Stearic Acid, found in fats such as shea butter and cocoa butter, helps harden the bars. It acts as a foundational structure for the bar itself. Stearic acid alone creates a very creamy, tight foaming lather. 

Palmitic Acid: 

Palmitic Acid, which is heavily prevalent in palm oil, also helps create long lasting bars, that harden faster. The lather is soft, and dense. While it doesn’t create large bubbles, it plays an important role in giving soap its structure and a more substantial feel.

Conclusion 

Soap isn’t just a single ingredient—it’s an ecosystem. A balance of fatty acids, alkali, and formulation choices that determine how it cleans, lathers, and feels on your skin. Even true soap is built from components that shape how it feels in the shower. Syndets are mechanically designed and lab certified to feel incredible, time and time again. 

In our next episode, we’ll dive back into the history of commercialized soaps throughout the world. Pear’s, Ivory, Dial, Dove, and even modern soap makers like Dr. Squatch. How did they come about? Who could afford them? When did the artisan soap market explode? All this and more, when we keep the conversation going about soap. 

Thanks For Reading, 

Michael