We use soap every day. We lather it between our hands, scrub, rinse and move on without giving much thought to what's actually happening.
But soap is doing something pretty interesting.
Water alone isn't particularly good at removing oils and grease. Oil and water don't exactly get along. Soap helps bridge that gap, allowing oils and grime to be carried away with the rinse water.
And the reason it can do that comes down to the unusual structure of a soap molecule.
So, if you've ever wondered how a simple bar made from fats, oils and lye actually gets things clean, here's the science behind it.
How does soap actually work?
A soap molecule has two very different ends.
One end is hydrophilic, meaning it is attracted to water.
The other end is hydrophobic, meaning it avoids water and is attracted to oils and grease.
That combination is what makes soap so useful.
When you wash with soap and water, the oil-attracted ends of the soap molecules associate with oily material while the water-attracted ends remain in contact with the surrounding water. As you scrub, soap molecules can organize into tiny structures called micelles, with oily material held within them.
The micelles remain dispersed in the water, allowing the oil and grime to be carried away when you rinse.
In other words, soap helps water clean up something water isn't very good at handling on its own.
Pretty clever for a bar that looks so simple.
It all starts with fats, oils and lye
Before soap can clean anything, we have to actually make it.
Traditional soapmaking relies on a chemical reaction called saponification.
At its simplest:
Fats or oils + lye → soap + glycerin
The fats and oils we begin with contain triglycerides. When they're combined with an alkali such as sodium hydroxide, commonly called lye, a chemical reaction takes place. The result includes fatty acid salts, which are soap, along with glycerin.
That means the finished bar isn't simply a mixture of oil and lye that hardened in a mold.
A chemical reaction has taken place and new substances have been formed.
The FDA describes traditional soap in much the same way: fats or oils are combined with an alkali such as lye, producing the fatty-acid salts that make up soap. Properly made traditional soap does not have lye remaining in the finished product.
That's one of the things we love about traditional soapmaking. The process may be old, but the chemistry behind it is pretty remarkable.
So why does soap lather?
This is probably one of the first things most of us associate with soap.
Water. Soap. Bubbles.
But here's something worth knowing:
More bubbles don't necessarily mean more cleaning power.
Soap is a type of surfactant, which means it affects the way water behaves, including reducing its surface tension. That contributes to the bubbles and foam we recognize as lather. The amount and character of that lather can vary depending on the fatty acids present in the soap and the formulation of the bar.
A big, bubbly lather can certainly be enjoyable.
But those bubbles aren't little scrubbers doing the cleaning.
The important chemistry is happening at the molecular level as soap interacts with water and oils.
Why different oils make different bars
This is where soapmaking becomes both chemistry and craft.
Not every fat or oil produces exactly the same soap.
Different fats and oils contain different combinations of fatty acids. Those differences influence characteristics of the finished soap, including how firm the bar becomes and the type of lather it produces.
That's why choosing the fats and oils in a soap recipe matters.
At Del Toro Ranch, we don't choose an ingredient simply because it sounds good on the front of a label. We formulate our bars with the finished soap in mind.
Our Signature Bar uses a blend of plant-based oils and organic shea butter.
Our Tallow Bar begins with grass-fed and finished beef tallow combined with organic oils.
Our Coconut Bar takes a different approach altogether, using 100% organic virgin coconut oil.
Different recipes. Different characteristics.
Same basic chemistry.
What happens after the soap is made?
Once cold-process soap has been mixed and poured into molds, we're not finished.
The bars still need time.
After they're unmolded and cut, our soaps are allowed to cure. During this period, excess water gradually evaporates from the bars. This helps create the firm, long-lasting bar we want before it ever reaches your sink or shower.
This is one of the reasons handmade cold-process soap can't be rushed.
There's mixing day.
There's cutting day.
And then there's waiting.
At least 6 weeks of it.
Sometimes the simplest products require a little patience.
Simple ingredients. A lot of science.
A handmade bar of soap doesn't look particularly complicated.
And that's part of what we like about it.
But behind that simple bar is chemistry that has been understood and used in one form or another for generations: fats and oils transformed through saponification, soap molecules interacting with both water and oil, and micelles helping carry oily material away in the rinse water.
We don't need to add fragrance or dyes to make any of that happen.
Soap already knows how to do its job.
For us, that's another good reason to keep things simple.
Want to see traditional soapmaking put into practice?
Explore our handmade Signature, Tallow, Coconut and Shop Bars, all made in small batches without added fragrance or dyes.
Real Ingredients. Clean. Simple.
Sources & Further Reading
U.S. Food & Drug Administration. Frequently Asked Questions on Soap.
Read the FDA's explanation of traditional soap
Chemistry LibreTexts. Cleaning with Soap.
Read more about how soap interacts with oil and water
Chemistry LibreTexts. Soaps and Detergents.
Read more about saponification and soap chemistry
