Why Do We Think Soap Works Only When It Lathers and Foams?

Have you ever used a cleaning product that didn’t bubble and foam? You may have wondered if the product was even working.

While we often associate bubbles with effective cleaning, many soaps do not actually need to foam to clean well. In fact, companies often add foaming agents to soaps, detergents, shampoos, and other cleaning products so that people will think the products are working.

Why do we equate bubbles with cleaning power? To explain our obsession with soap suds, we first need to understand how soap works.

What Is Soap and How Soap Works


The active chemicals in soaps and detergents are comprised of molecules called surfactants, otherwise known as surface active agents. They are long, pin-shaped or tadpole-shaped molecules that can bind to both water and oil. The pin-shaped head of the molecule likes to bind to water, meaning it is hydrophilic. The long tail of the molecule likes to bind to oil, meaning it is hydrophobic.

The molecule is so strong that the tail draws the oil away from whatever surface it is touching into the water, where it can then be washed away.

Bubbles are formed when the hydrophobic, oil-loving ends of the molecules try to escape from the water molecules. This pulls the water molecules apart, reducing the strength of the water’s surface tension and allowing it to stretch and trap small pockets of air.

Even though soap does not actually kill bacteria, the long tail of the molecule also bonds to pathogens, allowing them to be washed off your skin.

Technically, soap refers to surfactants made from naturally occurring fatty acids such as olive or coconut oil, while detergents are made by combining several chemicals together. Most “soap” used today is actually detergent.

Brief History of Soap

Many Ancient Near Eastern cultures, including Egypt, Babylonia, and Rome, left behind evidence of soap making as long as 5,000 years ago. An ancient Roman legend recounts the discovery of soap on Mount Sapo, from where the word soap may have originated. Grease from the gods cooking meat dripped down onto ash where humans then discovered it removed dirt and oil.

Soap continued to be made with animal byproducts such as tallow or lard or with natural oils until the invention of detergents and chemical surfactants.

The Dish on Lather

Now it’s time to answer the real question. Why are we so hooked on bubbles?

Former professional soap makers Aja and Billy Smart say that before modern detergents, foam and lather were likely a general indicator that soap was actually cleaning, though we didn’t understand how on a molecular level.

Go check out Aja’s fiber art business, Strand Texture, and Billy’s dog-walking business, Adventures from A to B.

Now, though detergents and many natural cleaning products can clean without foaming, we still associate bubbles and lather with cleanliness. Companies add foaming agents to many products to meet our expectations.

But in some cases, foam actually helps soap clean better.

For example, when soap forms bubbles, it allows the surfactants to sit on surfaces longer, increasing the time the surfactants can lift up dirt and grease. If you have ever left a pan full of soapy water overnight in the sink, you know that you can’t simply pour soap into the pan without water. It has to form bubbles to be effective.

On the other hand, if you have ever run a dishwasher with regular dish soap and watched bubbles pour out onto the floor, you will know that foam actually can hinder the cleaning process, such as in dishwashers and washing machines.

Are Foaming Agents Bad for You?

One commonly used foaming agent is sodium lauryl sulfate, a very effective surfactant found in detergents, shampoos, and toothpaste. While it produces the foam we are accustomed to, it can strip natural oils from your hair causing damage.

If you are concerned about sodium lauryl sulfate or other foaming agents in your cleansers, consider switching to natural soaps. But, if you still want the feel of lather, Aja Smart says that coconut oil in soap can produce the best bubbles.

This article is a continuation of a series about how I’m making the problem of building up your portfolio entertaining and productive.

In short, I created a Fiverr gig offering to write blog posts for $10 and asked my friends if they had anything they would like to be researched. They get a concise summary, while I add something to my portfolio and boost my Fiverr profile. You can read all about it here.

The above is the third of four such pieces I will be writing. Because this is very much in the style of a blog post that would require heavy SEO-optimization, I also used this as an opportunity to hone my SEO skills.

Leave me a comment if you spot any ways I could improve my writing.

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