Fancy Foams with Shampoo Science

Introduction

Do you like your hair shiny and beautiful? The key to keeping your hair nice and clean is to use a good shampoo. But what exactly makes a good shampoo? You might be surprised to hear that every new shampoo has to pass lots of scientific tests before it is considered good enough to be sold. Many different shampoo recipes are compared to decide which one is the best for the consumer. One of these tests assesses the foaming behavior of the shampoo. You probably trust a shampoo that makes lots of foam more than one that doesn't make any foam at all! In this activity, you will become a cosmetic scientist and put different shampoos to the test. Which brand do you think creates the most foam and which foam lasts the longest?

Background

Shampoo is by far the most common product used for hair treatment across all hair colors and lengths. Although many different shampoo products are available in stores, they all have the same purpose: to clean dirt and grease from your hair and scalp. If you have too much grease in your hair, it looks oily. How can shampoos remove all this built-up grease? For this, shampoos contain specific ingredients called surfactants, which are the main ingredients in shampoos besides water. Surfactants are unique chemicals as their chemical structure has a hydrophobic (water-repelling) tail and a hydrophilic (water-loving) head. This property allows them to react with both water and grease, which normally doesn't mix with water.

Although its cleaning power is probably the most important criteria for a good shampoo, there are many other aspects that decide the quality of a shampoo. Besides surfactants, there are also additives in each shampoo that optimize its look, feel, smell, or performance, such as additional foam builders, thickeners, conditioning agents, or preservatives. For example, the ability to create lots of foam and the stability of the foam is important because people associate more foam with more cleaning power. Although this is not necessarily true, a shampoo sells much better if it makes more foam. Therefore, additional surfactants that have a strong capability to produce foam are used as foaming agents.

Scientists constantly research new shampoo recipes and have developed specific tests to assess every new product they create. This allows them to compare different shampoo recipes to find the one formula that performs best overall. In this activity, you will perform such a test yourself and find out which of the shampoos in your selection creates the best and the longest lasting foam!

Materials

Preparation

Procedure

Observations and Results

Did you create lots of foam? Most of the store-bought regular shampoo should have produced lots of foam once you started shaking it. You might have even seen a little foam formation already when you poured the shampoo solution into the glass. This is because these shampoos contain lots of surfactants and foam builders. When you shake the glass, you create lots of gas bubbles that get trapped in the shampoo solution and result in the foam you see. The surfactants or foaming agents facilitate the formation of foam and stabilize the gas bubbles in the solution.

However, the foam is not stable forever! In fact, you should have observed that the amount of foam quickly decreased over time. You probably saw that the bottom level of the foam quickly rose to a higher level because the gas bubbles in the solution eventually collapse. The volume of foam that you produce for each of your shampoos depends on how much surfactants and foaming agents they contain. Solutions that do not contain any of these substances, such as water, do not create any foam, which you should have noticed in your last test.

Cleanup

More to Explore

• Shampoo, from How Products are Made at Madehow.com
• Secrets of Shampoo, Special to The Washington Post
• Types of surfactants in your shampoo, from hairmomentum.com
• Make Your Own Shampoo and Test How It Performs!, from Science Buddies
• Science Activity for All Ages!, from Science Buddies

Credits