Make Your Own Shampoo and Test How It Performs!

Do you care about your hair and how it looks? Most likely, yes. After all, your hair is visible to everyone and you don't want it to appear all greasy and messy! As it frames your face, the hair is probably one part of the body that many people care most about. Just think of all the hair care products that you can buy: shampoo, conditioner, spray, mousse, or wax, just to name a few. Shampoo is by far the most common product used for hair treatment across all hair colors and lengths. Some people use "organic" shampoos, or even make their own recipes, because they do not like the synthetic chemical products in the shampoos in the store. Although there exist many different shampoo recipes and products in the stores as shown in Figure 1, they all have the same purpose: to clean your hair and scalp from dirt or grease. Your hair tends to get greasy because it accumulates an oily substance, also called sebum, that is made by your body to moisturize your scalp and protect your hair from drying out. If you have too much of it in your hair, it looks oily. How can shampoos remove all this build-up of grease?

To find out, we will take a closer look at the shampoo ingredients, or its recipe, also called formulation. Besides water, surfactants are the main ingredients in shampoos. They have names such as sodium lauryl sulfate, sodium laureth sulfate or cocamidopropyl betaine. Surfactants are unique chemicals as their chemical structure has a hydrophobic (water-repelling) tail and a hydrophilic (water-loving) head, as shown in Figure 2. This property allows them to react with both water and oil, which normally doesn't mix with water.

The surfactants in shampoo account for its cleaning power. When washing your hair, the part of the surfactant that is compatible with oil (hydrophobic tail) sticks to the greasy and oily materials in your hair, whereas the water-soluble part, the hydrophilic head, aligns with the water. If many surfactant molecules do this, they form a micelle structure, which traps the grease and oil in its middle, as shown in Figure 3. This way, the oil that is trapped in water with surfactants can easily be washed away, while water without surfactants fails to remove the grease from your hair.

Figure 3. Schematic view of a micelle structure (not to scale). In a micelle, the hydrophobic tails of surfactant molecules stick to the oily particles, whereas the hydrophilic heads align with the surrounding 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. In fact, a shampoo needs to meet many requirements to be accepted by customers like yourself. This is why, besides surfactants, there are also so-called additives in each shampoo that optimize its look, feel, or performance, such as additional foam builders, thickeners, conditioning agents, or preservatives. For example, the ability to create lots of 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 (synthetic) surfactants are used as foam builders that have a strong capability to produce foam. Just think about what you love about your favorite shampoo! You probably would not like it if it would not meet all the criteria below (and probably some more):

1. It removes the dirt and grease from your hair
2. It makes a good amount of foam so it feels nice and you can spread it easily through your hair
3. It does not stick to your hair and can easily be rinsed
4. It makes your hair shiny and soft
5. It smells nice
6. It does not irritate your scalp or your hands

This is why the cosmetics industry and world of beauty products needs scientists! Scientists constantly research new shampoo formulations and developed specific quantitative tests to evaluate each of these properties for every new product they create. The combination of these specific tests allows them to compare different shampoo recipes based on quantitative data to find the one formula that performs best overall. For example, they can find out which ingredients help to remove grease most efficiently or make the best foam.

In this science project, you will create your own shampoos using two different recipes based on organic ingredients. Many people prefer "organic" or natural beauty products as they want to avoid synthetic (or man-made) chemicals that might damage their skin or could potentially be harmful. The most common organic replacement of synthetic surfactants are soaps based on olive or coconut oil. Castile soap, a surfactant made from olive oil, is one example that you will use in this project. Other natural shampoo formulations try to avoid surfactants entirely as they can throw off the pH balance of your scalp and might irritate your hair and skin. You will also prepare one of these shampoo recipes without surfactants which is based just on coconut milk. Do you think these organic shampoos are as good as a store-bought product? Start the shampoo testing and find out! 

Terms and Concepts

• Shampoo
• Sebum
• Formulation
• Surfactant
• Hydrophobic
• Hydrophilic
• Micelle
• Additive
• Synthetic
• pH

Questions

• Why do people use shampoo?
• What ingredients are in shampoo? Can you find out the purpose of each of them?
• Which properties are most important for a shampoo and how would you test these? Which tests do commercial companies use?
• What are the reasons why some people use their own organic shampoo formula? Do you think these products can perform as well as synthetic shampoo formula?