What's in Shampoo - About Surfactants

This is part of a mini-series of shampoo, body wash and soap products articles. Read the first part here, or jump straight into the technical stuff.

Shampoo (and other soapy, lathery products) work as they do because of surfactants.

Surfactant - What's in a Name

The name surfactant is a compound of 3 words: surface + active + agent. Just as the name is a compound, a surfactant is a sum of several parts. Surfactants have versatile uses and properties – one is the ability to bind oil and water (act as an emulsifier).

Other abilities include wetting, dispersing, anti-foaming and – what we all have come to expect from our shampoo – foaming.

Some surfactants are negatively charged, some positively charged, some swing both ways (just to make things fun) and some are neutral.

What About Shampoo?

Surfactants are used in a multitude of different ways, but for making shampoo (and body wash), there are 4 main categories involved. Because no surfactant can quite do the job on its own, it's necessary to group them in order to create a shampoo.

It's kind of like getting a group of musicians together – each one plays a vital part in the final composition.

Anionic, Cationic, Amphoteric and Non-ionic

Meet The Fab Surfactant Four

Anionic

Anionic surfactants are great at foaming but can be irritating for the skin. Anionic means negatively charged.

Cationic 

Cationic surfactants will reduce the foaming action of a mix, but they are forgiven for this because their function is to be conditioning. Cationic means positively charged.

Amphoteric 

Amphoteric surfactants bring mildness to a mix, but have much less foaming ability than their anionic counterparts. They are therefore usually combined with anionic surfactants. Amphoteric surfactants can be either positively or negatively charged – depending on the pH of the mixture.

Non-ionic 

Non-ionic surfactants are quite useful as emulsifiers. Their addition to a mixture will give it body and keep everything from separating, but will also tend to cause a reduction in foaming action. Non-ionic surfactants are neutral.

This is Just the Headlines

Within each of these categories there are numerous surfactants to choose from. (For example, the controversial SLS's are anionic). It is not unusual to see a more than one surfactant from the same category in a shampoo – they counterbalance and/or enhance each others properties depending on what the shampoo is expected to do (cleanse baby's hair, help battle dandruff etc etc).

Combined properly, the right mix of surfactants make up the base of the perfect shampoo (or body wash) that does everything you expect it to do and has you singing in the shower.


Next installment, I'll get into (some) details about some of the surfactants I work with in my products as well as taking a look at some of the ones I don't use. Stay tuned!