In previous posts, we here at the Beauty Brains talked about the ingredients in shampoo and how they’re mixed together. This post talks about how shampoo actually works to clean your hair.

Dirty Tricks

The reason you want to wash your hair in the first place is because it’s dirty – but how does it get dirty? There are several ways: The sebaceous glands in your scalp secrete natural oils (kind of chemically similar to olive oil) that make your hair feel greasy; then you ‘ve got perspiration which deposits salts and other junk on your hair and scalp. On top of that mess you have smoke , pollution, and dust that your hair picks up from the environment. And let’s not forget the styling residue from hair spray, gel, mousse, and putty you might have used. Now, you might think that getting this stuff off your hair would be simple, but the process of cleansing is really ingeniously sophisticated.

Wash and wear

For the most part, all this residue on your hair is not very water soluble – in other words if you just rinse your hair in water you wouldn’t get rid of it all. Enter the shampoo with its surfactant (aka detergent) molecules. These molecules are designed to remove these water insoluble contaminants by working as tiny chemical bridges. (They link oil and water together.)

If you were to look at these molecules under a microscope , you would see they consist of two parts: One end of the molecule is attracted to water, and at the other end to oil. This structure gives surfactants the unique ability to combine oil and water and it also allows them to create foam as well. This handy little piece of chemisty is one of the most important properties of cosmetic ingredients and we’ll talk about it more in a future post .

So, when the shampoo is applied to your dirty hair, these tiny chemical cleansers spring into action and “seek out” the drops of oil, dirt, and yesterday’s Sebastion hair spray. The surfactants actually surround these contaminants and lift them off your hair. Once all the undesirable dirt is lifted off your hair the surfactants keep it suspended in the rinse water so it goes down the drain, not back on your hair.

So there you have it – that’s how shampoo cleans your hair. And if you’re wondering how a 2 in 1 shampoo cleans and conditions your hair at the same time, well, that’s a different post!

In How Shampoos Work – Part 1, we talked about the ingredients used in shampoos and their functions. Here in Part 2, we’ll deal with the question – how are those ingredients mixed together to create a shampoo?

Lab batches and scaling up

The process actually begins in the laboratory where cosmetic formulators blend small amounts of chemicals to understand how they behave when they’re mixed together. Once the chemists have a formula and they’re satisfied with their ability to make a few pounds of shampoo in the lab, they then translate these mixing instructions into a version suitable for making several thousand pounds in the manufacturing plant. This process of is “scaling up.”

In the manufacturing plant, shampoo is typically made in big stainless steel tanks, as large as 3000 gallons. (That’s over 20,000 bottles of shampoo!) These tanks have an outer shell that can be filled with either hot or cold water – that’s how the batch is heated or cooled. The tanks also have mixing blades that turn the tank into kind of a giant blender.

Ok, now we’ve got a formula, instructions on how to manufacture it, and a giant blender. Let’s make some shampoo!

Charging the tank

The first step is to fill the tank with some portion of the water, which is the solvent for the system – it dilutes the the rest of the ingredients to the proper concentration. A special type of water , known as deionized water , is used to ensure the product is as pure as possible. Depending on what else is in the formula, the water may be heated to make the other ingredients dissolve faster.

After the water , the other ingredients are added in a specific order. The surfactants are usually added early in the process. These ingredients range in consistency from being water thin to very jelly like. These may be dumped into the tank from drums or pumped in from other chemical storage tanks. Care must be taken when adding surfactants because they may cause excessive foam. (Remember these ingredients are detergents.) The surfactants may require heating and mixing to fully dissolve.

Heating and cooling

As the batch reaches its peak temperature, any solid ingredients that require melting may be added. These include opacifiers (ingredients that give the shampoo a pearly appearance ) and certain conditioning agents. Once all these ingredients are thoroughly mixed together, the batch is cooled by pumping cold water through the tank’s outer shell. As the batch continues to mix the cold water cools the shampoo and the product begins to thicken.

Once the batch is sufficiently cooled the rest of the ingredients are added. Some ingredients, like fragrance, botanical extracts, and preservatives must be added at the end of the batch because they are heat sensitive. Adding these ingredients in the wrong order can result in a product that either doesn’t smell right or one that will grow too much bacteria.

Checking the specs

After the bench is finished, adjustments may be made using the control agents . To make sure that every batch of product is the same (or at least ALMOST the same) every product has a set of predetermined specifications. These specifications ensure the product has the right odor , appearance , viscosity, etc. If the product is “out of spec,” control agents maybe added to adjust it. For example , if the shampoo is too thin more salt maybe added to the batch to thicken it.

Filling the bottles

Upon final approval the batch is then pumped through a series of pipes to the filling equipment which puts the product in the bottles. Most modern manufacturers have a fully automated process in which the bottles travel down a conveyor line, pass under a filling head that squirts product into the bottle. Then they move down the assembly line to a capping machine that applies the closure. Finally, the bottles are boxed and placed on a pallet for shipping to stores. From there, next stop: your bathroom!

So there you have it – the Beauty Brains take on shampoo mixing. In Part Three of how shampoos work we’ll deal with how they actually clean your hair.

Having worked in the cosmetic and beauty industry for many years, we here at the Beauty Brains have learned a bit about how cosmetics work. Over the coming months we will write about all kinds of products and how they work. This first entry is about shampoos.

Let’s break down the question into three parts:

This first post will define what ingredients are used in shampoos, the second part will describe how the formula is manufactured, and the third part will explain how the product actually works on hair.

Part 1: Shampoo ingredients can be broken down into the following basic categories:

Surfactants
Surfactants are the primary functional ingredients in shampoo. A surfactant is simply a type of detergent. Although sometimes surfactants are referred to as soaps, this is not exactly accurate. A soap is a special type of surfactant, but not all surfactants are soaps. Surfactants make the shampoo foam; they also dissolve grease and oil from your hair. Surfactants are commonly used in almost every type of cleansing product, from toothpaste to hand soap to body wash.

Thickeners
Shampoos are typically thickened by a reaction between the surfactants and salt. Formulators may also add special thickening agents known as polymers.

Preservatives
Preservatives are added to the formula to ensure the product doesn’t become contaminated by bacteria, mold, or yeast. Common preservatives include parabens and urea derivatives.

Color
A variety of dyes maybe added to the shampoo to impart a pleasing color. In the vast majority of shampoos, the dye has no functional purpose at all – it’s just there to make the shampoo look nice. There is a special sub-class of shampoos that are color-depositing. They contain special staining dies that can help give the hair a little bit of color.

Conditioning agents
A good shampoo not only cleans the hair, it moisturizes as well. The conditioning agents used in shampoos are typically polymers such as those derived from cellulose or guar, or silicones. Typically the silicone must be chemically modified to be soluble in the shampoo system. Two – in -1- shampoos have higher levels of conditioning agents so a separate rinse out conditioner is not required.

Control agents
Control agents are added to the formula to help adjust its physical properties. For example, an acid or base may be added to raise or lower the pH. Thickeners, as the name implies, control how thick or thin the product is. (The scientific term for this measurements a is “viscosity.”)

Fragrance – fragrance is extremely important to a shampoo. In addition to covering the chemical odor of the product, a good fragrance support the image of the product. For example, research shows that consumers think a deep cleansing shampoo works better when it has a citrus fragrance. Moisturizing shampoos seem to condition better when they have a rich, “milky” fragrance. In future posts we’ll deal with the impact of fragrances in cosmetics in more detail.

Featured ingredients
Marketers frequently add featured ingredients to their formulations to make them more appealing or to support to a certain marketing story. In the deep cleansing shampoo example described above, one would expect to find a citrus extracts like tangerine peel or lemon zest in the formula. While these ingredients do serve to make the product more appealing, they typically do not perform any function.

Now that you have a fundamental understanding of what goes in a shampoo, you’re ready to learn about how these ingredients are put together into a finished product. Check out Part 2 of “How Are Shampoos Made” next.