Monday, 18 April 2011

Sodium Laureth Sulfate and Ammonium Laureth Sulfate: What Are These Guys Doing In Your Shampoo?

Laureth ... Lauryl ... What's The Difference And Should You Care?

My first post about Ammonium Lauryl Sulfate and Sodium Lauryl Sulfate last week caused a little bit of an uproar around here, distracting me from my usually calm world of hair clips.

Most of the activity happened by email, but there were a couple excellent comments, which will probably take me the rest of 2011 to answer completely.

To add to the thrillingness of my life, I *just this very morning* received my new book, Biophysics of Human Hair: Structural, Nanomechanical and Nanotribological Studies by Bharat Bhushan.

When I opened the envelope, Claire peeked over my shoulder and said, "C-o-o-o-o-o-l!" while my middle daughter rolled her eyes up and sighed (with love and admiration, naturally).

More About Detergents In Your Shampoo

I wanted in this post to move on to the secondary detergent which virtually always gets paired with whatever "lauryl sulfate" ends up in your shampoo formula, which is its "laureth sulfate."

Sodium laureth sulfate(SLES) and ammonium laureth sulfate (ALES) are basically detergents, which combined with the lauryl sulfates (SLS or ALS) make up roughly 8-10% of your shampoo.

The term "laureth" means that a laurel salt has been ethoxylated before neutralisation. You might read that SLES for example is derived from SLS, so therefore is "just as bad," assuming that SLS is "bad" at all, of course. In fact both ingredients come originally from palm or coconut oils and then go down different production paths, with SLES having one extra step along the way.

This process results in a detergent that has better foaming qualities and a more attractive touch feel, helping your shampoo to be more gloopy and less liquid. This characteristic makes it easier for you to control the amount of shampoo you pour out of your bottle, rather than having watery shampoo running all over and off your hand.

Some websites you will find on the internet scorn the value of these qualities, which is fair enough. But speaking as a hobby soapmaker myself, I could make a soap purely out of olive oil, for example. But pure olive oil soap doesn't lather, so it's a little unsatisfying to use. Add a little coconut oil, and then you're talking bubbles!

What Is Meant By "Harsh" Detergents?

SLES has been profiled as being milder on the skin than SLS, and that it is used as some sort of pH balancer in shampoo. This is completely misleading.

First of all, pH is what is meant by whether something is "mild" or "harsh" in personal care products. While 7.0 is neutral, deviations from neutral don't have too much to do with how it feels on your skin.

The pH of the acid mantle of adult skin is, as you can tell by its name, acidic and ranges from 4.0 to 5.5. Preservation and support of the acid mantle is important for the ongoing health of your hair and skin. For this reason, commercial skin and hair care products are formulated to fall towards this range.

In newborn babies, skin pH is on average closer to 7.0, demonstrating the importance of using soap, lotions and shampoo which are specifically formulated for babies. Within only a few months after birth, however, their skin pH falls gradually down the scale to 4.5 to 5.0, rendering these specialised products less important.

If you were to look at ALS, ALES, SLS and SLES in isolation, the pH can vary widely depending on specific formulation and solution concentrations between suppliers, but as a snapshot from Lubrizol as an example the pH ranges in a 10% solution appropriate for use in shampoo are as follows:

ALS: 6-7
ALES: 6-7
SLS: 7.5-8.5
SLES: 7.5-8.5

By way of comparison, bath soaps tend to have a pH range of 7.0 - 9.0, while shampoo in normal commercial formulations have a pH typically of 5.0 - 6.0.

A shampoo pH of between 5.0 and 5.5 is often desirable because the slightly more acidic environment promotes a tightening and hardening of the cuticle scales even before drying, which helps make hair stronger and shinier once it is dry. More typically, shampoos have a pH of 5.5 to 5.8.

Interestingly, the pH of your eye is in the range of 6.5 to 7.6, and constantly changes according to how active your tear glands are in response to the immediate environment.

When designing a shampoo, the chemist first of all wants to achieve a pH that supports first your hair, then your skin, and finally takes in consideration your eyes.

So it is a leap in logic to say that SLS is too harsh for your hair, and SLES (or either of the ammonia based sulfates, for that matter) is better because it is less irritating is not really considering the bigger picture of what you actually want  to achieve by using any shampoo at all in the first place.

Further, in order for the shampoo to be "gentle" on your hair the pH must be greatly corrected to make it more acidic.

Why Use These Sulfates When There Are Other Detergents?

One of the primary benefits of using these particular detergents is that they blend very well with a wide range of other ingredients that perform well in your hair, such as anti-static agents, conditioners and chelating agents. All of these categories of ingredients help protect the integrity of your cuticle during washing and styling.

The goal in creating a shampoo formula is to design something that is easy for anyone to use without a lot of explaining, and that gives most people on average a good result with their hair.

Generally speaking, I find most shampoos pretty okay. Depending on what your goals are for cleaning your hair, you should simply use less or more as required on any given day.

I, for example, don't need to clean my hair very much because firstly, my hair is quite porous and secondly, because I don't use any styling products on my hair there's very little that actually needs washing away.

My recommended method of diluting your shampoo is to daub the tiniest pearl of of shampoo you can get from your bottle, lather it up in your hands, and then rinse one hand off. Use the lather that's left only on the spots on your scalp that actually feel like they could use cleaning.

If your hair is really oily or you've used mousse or gel that needs washing away, then use fractionally more.

Finding the right amount of shampoo to fit your needs takes experimentation, but it is worth it. Not only will you save a lot of money, but you will find in time that your hair becomes better behaved and more manageable for you.

To read more about this topic, read my earlier blog post about shampoo and what it's really for.

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