What is Soap Made Of? Ingredients Explained

The word soap is used very generically. We say that it’s soap that cleans our clothes, our dishes, our hands, our houses. Various cleansers do all these things, but they aren’t all soap.

True soap has a fairly narrow definition. And it all comes down to ingredients and what soap is made of.

What is Soap? A Soap Definition

We all know that soap cleans. In fact, a dictionary definition of soap will tell us exactly that. Soap is a cleansing or emulsifying agent.

But so are some of those other cleansers I mentioned. The difference is the next part of the definition and the ingredients of soap.

Where other cleansers are made of sulfates and other detergents, true soap is made of a few simple ingredients.

Specifically, true soap is a salt of a fatty acid. Simply put, mix a fat or oil with an alkali, and you’ve got soap.

But what are these fats and oils? And what’s an alkali? And is that all that’s really needed?

Let’s take a look at each of the ingredients that make soap.

Soap Ingredient List

Making soap requires three ingredients. Every bar of soap begins with fats and oils, an alkali, and water.

Fats and Oils

Fats and oils are the foundation of soap. Fats are solids like butter or lard. Oils are liquid at room temperature, like olive oil or corn oil.

The fats and oils in a bar of soap determine the texture and qualities of the bar.

Fats and oils are triglycerides. That’s the chemical term and it indicates the chemical structure of these substances. That means that every fat or oil contains 3 fatty acid chains.

Every fat and oil contains specific fatty acids. Some chains are straight, some bend, some are loose, and some are packed tight. At any rate, every type of fatty acid chain has its own properties.

Fatty Acid	Properties It Lends To Soap	Properties it Lends To Skin
Lauric Acid	Hardness, Cleansing, Fluffy Lather	Anti-bacterial, Emollient, Strengthening
Linoleic Acid	Conditioning	Balancing, Rejuvenating
Myristic Acid	Hardness, Cleansing, Fluffy Lather	Softening
Oleic Acid	Conditioning	Emollient, Restoring, Nourishing
Palmitic Acid	Hardness, Stable Lather	Emollient, Restoring, Softening
Ricinoleic Acid	Conditioning, Fluffy Lather, Stable Lather	Humectant, Emollient, Anti-inflammatory
Stearic Acid	Hardness, Stable Lather	Fortifying, Protective, Emollient

 

And every fat or oil has its own quantity of certain fatty acids. In the following chart, the fats and oils are listed on the left side with the fatty acids across the top.

	Lauric	Linoleic	Myristic	Oleic	Palmitic	Ricinoleic	Stearic
Avocado		6-18%		36-80%	7-32%		1.5%
Castor		3-4%		3-4%		90%
Coconut	39-54%	1-2%	15-23%	4-11%	6-11%		1-4%
Grape Seed		58-78%		12-28%	5-11%		3-6%
Hazelnut		7-11%		65-85%	4-6%		1-4%
Lard		6%	1%	46%	28%		13%
Olive		5-15%		63-81%	7-14%		3-5%
Palm		9-11%		38-40%	43-45%		4-5%
Rice Bran		32-47%		32-38%	13-23%		2-3%
Tallow		2-3%	3-6%	37-43%	24-32%		20-25%

 

A good bar of soap will use multiple fats and oils that complement each other. And knowing the qualities of the fats and oils, a bar can be designed for specific skin types and conditions.

Alkali

As the name suggests, alkalis are alkaline. They can be so alkaline that they can give a chemical burn.

Alkalis are chemical compounds that release hydroxide ions when dissolved in water. It’s the hydroxide ions that are the real ingredients in soap.

The two alkalis used in soap are sodium hydroxide (NaOH) and potassium hydroxide (KOH). Both are commonly called lye. Potassium hydroxide is also called caustic potash.

Because of the molecular size and shape, sodium hydroxide makes a solid bar soap and potassium hydroxide makes liquid soap.

Since the hydroxide ions are released when the alkali is dissolved in water, this leads us to the final of the three ingredients needed to make soap.

Water

Water is necessary in soap only for the purpose that it provides the place for the alkalis to dissolve and release the hydroxide ions.

Chemically, water is not actually part of the final soap. This said, there is a small amount of water molecules left in the soap, just as moisture, hence water, is pretty much everywhere.

Once the fats and oils completely mix with the alkali, the water slowly, mostly, evaporates.

In the case of liquid soap, water may be added for the sake of texture and thickness.

How is Soap Formed? A Little Soap Chemistry

As we’ve seen, soap is formed when a fat or oil molecule joins with a hydroxide molecule.

To make that hydroxide ion available, an alkali must be dissolved in water. Without water, the alkali cannot dissolve and make the hydroxide ion available to the fats and oils.

Chemistry teaches us that everything is made up of atoms. Atoms can bond and make molecules.

Fats and oils are molecules. Alkalis are molecules. Water is a molecule.

When the alkali is dissolved in water, the molecule breaks apart. When the water with the dissolved alkali is added to the fats and oils, the fat and oils molecules break apart. Those fatty acid chains disconnect from the glycerol that was holding them together.

These molecules do not break down into single atoms. At this point, they are unstable molecules. They need new partners.

By the way, the water molecules do not break apart.

I think of water as the dance floor where all the fatty acids dance and mix with the hydroxides.

The fatty acids and hydroxides rearrange and make new bonds. No longer are there any fats or oils. No longer is there an alkali (or lye).

Those molecules have mixed and matched and made that salt of a fatty acid that is soap.

But what happened to the glycerol? It forms glycerin, a natural humectant (something that pulls water to itself and is thereby moisturizing).

All the molecules are bonded securely.

The dance has ended. The couples are all matched up while a few good friends look on.

Soap is formed and glycerin makes it richer.

Other Ingredients in Soap

Soap is such a humble chemical creation. Oil, lye, and water. They’re all that are needed.

Three basic ingredients form a substance that supports life and health simply by cleansing away dirt and bacteria.

Yet, there are countless other ingredients to add that can offer even more benefits. On the downside, there are also ingredients, generally synthetic, that can adulterate soap.

I don’t want to compromise any of the wonders and value of handmade soap, with its healthy fatty acids and natural glycerin.

Essential oils for scent and botanicals for color both offer more benefits and support what’s already there with the fatty acids.

Essential oils can offer a little aromatherapy. And most botanicals used for color also have features that support skin health.

None of these natural additives spoil the chemistry of true soap.

So next time you reach for a bar of soap, or other cleanser, take a look at the label. Is it soap? Does it have fats and oils that are giving you all the advantages of their fatty acids and glycerin?

At The Straddle Creek Soap Shop, enjoy real soap that treats your skin right!