Beauty in a Bottle: How Do Shampoos Work? Part 2: Mixing

In "How Do 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?


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!




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.

As the batch reachs 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 .

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.

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 - shampoo mixing made simple. In Part Three we'll deal with how the shampoo actually works on your hair . Look for part three of " How Do Shampoos Work? " in an upcoming post .