Thursday, May 20, 2010

Chemistry of your hair: Shampoo

What's the point of using a shampoo? It seems like a lot of people are touting the awesome power of the "no-poo" method, which is only using conditioner to wash your hair (see my post a little later today on this topic). Shampoo is intended to remove those things that might mess up your hair every day like sebum, sweat, environmental pollution, and styling products.

Sebum is steadily replenished by your scalp over the day through those sebaceous glands attached to your hair follicle. The amount of sebum produced varies from person to person, but usually reaches its maximum at puberty, and is affected by the seasons, the temperature, and hormonal variations.

Sebum is really sticky and can cement soil and other particles to your hair and scalp. Although brushing, combing, and contact with your pillow will redistribute the sebum, you can't remove it entirely by physical means because it's so sticky! And it means that the oilier your hair, the more stuff will get attached to it, like dirt particles, smoke, bits from rain water, skin flakes, and so on. It can oxidize like any other fatty acid, leading to that dirty hair smell you get when you haven't washed your hair in a while. (Click here for a post on rancidity of oils for more information.)

Sebum can be your friend! It is good at sealing the hair shaft and protecting it from the outside world and it does make your hair temporarily glossy. (Some hair types - like African hair - love sebum and actually see an increase in shine and less breakage when their hair is oiled!) But you do need to remove it because it really isn't that attractive to have seriously greasy hair.

Interestingly enough, the spread of sebum through your hair is increased when you blow dry it. So if you're a particularly greasy haired girl, leaving your hair to dry naturally can buy you more time between washings!

Proteinaceous matter from the desquamation of your scalp and your sweat can build up in your hair as well. And as I mentioned above, sebum attracts environmental pollutants, so washing your hair on a regular basis removes those pollutants, soils, and sebum to leave your hair fresh and clean.

How does shampoo remove these things from our hair? We know that surfactants lower surface tension (for a quick review, click here) but they're also effective at deflocculating soil and dirt clumps in our hair. (Deflocculating means "to disperse an agglomerate into fine particles and form a colloid" - in other words, to disperse a clump of something into finer particles. You might remember flocculation from the epic lotion fail post - this means for finer particles to clump together!) The shampoo keeps the fine particles in suspension so they can be washed away and not go back onto your hair or scalp.

Detergents work in a few different ways...
  • "Roll-up mechanism": Causes a rapid detachment of oils from your hair, scalp, body, and/or clothes, which are displaced by the surfactant. 
  • Micellular solubilization mechanism: The soils are solubilized into the micelles and washed away (this is dependent upon micelle concentration). It's all about displacing the oils in your hair and scalp with the detergent solution. 
  • Dispersion and emulsification: Soil particles are emulsified into the solution. Sebum might actually help this process. 
What are the goals of a shampoo? Our goal is to clean our hair...which means what? We want to create a lovely lathery, bubbly, non-toxic and non-irritating, fresh smelling shampoo that will...
  • remove sebum and soil from our hair and scalp
  • remove residue of styling products
  • leave hair in good condition after rinsing, meaning it can be combed or brushed when wet or dry
  • deposit lovely things like panthenol, conditioning agents, and so on
There are quite a few shampoo types to choose from, so we'll be taking a look at each of these and formulating a few recipes!
  • frequent use shampoo
  • basic shampoo
  • conditioning shampoo
  • 2-in-1 shampoo
  • anti-dandruff shampoo (we won't be making these)
  • medicated shampoo (we won't be making these)
  • baby shampoo
So join me tomorrow as we take a look at how to formulate a basic shampoo! 


Alittleofthisnalittleofthat said...

Are you open to people quoting your blog posts? I am a soap maker that is unconditional addicted to your information on hair care products. I have taken your teachings and applied them to my soap making, resulting in some fantastic hybrid shampoo and conditioners. I would like my customers to understand why surficants are so important and not the " devil " , soap crafters have really tried ruin their reputation.

Thank you,

Janet Stewart said...

Please help me !! I love this site, you are a genius and so informative. I live in South Africa, and its so hard to find all the products here. I am trying to find out why the shampoo I have made makes my hair feel like straw-its your exact recipe for CONDITIONING SHAMPOO FOR DRY HAIR WITH PEG-7 COCOATE, COCAMIDE DEA, OR WATER SOLUBLE OILS. I use coco betaine and Decyl glucoside as no SMC taurate in this country. Xanthum gum to thicken, geogaurd as preservative, I use half argan oil half emulsifier as no PEG or DEA available. Its great foaming etc but it makes my feels gross, like straw when its wet, its fine after conditioning but I don't like that feeling at all and am trying to figure out what causes it and how to prevent it. Thanks so much.

Susan Barclay-Nichols said...

Hi Janet. Can you please write out your exact recipe - the one you made, not the original one - and the process you followed as I can't help without that information. I need the names for things - for instance, emulsifier isn't enough information - to know what you used.

As an aside, you mention you followed my exact recipe, but you note many many changes. This wouldn't be my exact recipe with all those substitutions.

Janet Stewart said...

Yes you are right, not your exact recipe!!Phase A- 46% water, 1.5% Xanthum gum, 10% coco beatane, 15% decyl glucoside, 10% aloe vera liquid, 3%- water soluble oil (1.5% polysorbate 20 and 1.5% argan oil), 5% glycerin, 2% kera silk liquid (hydrolised protein), PHASE B- 3% Polyquat 7, 2% dimethicone, 1% cyclomethicone, 2% liquid panthenol, 1% geoguard, 2% essential oil. Its fabulous, my kids love it. Its just that I don't know whats causing this feeling like stiff straw (feels like my hair is synthetic after washing) that I don't like? Completely personal for me as I am so tactile, its a great formula. The PH was 5.5 . I am going to try Lauryl Glucoside and Coco glucoside to see if it improves this icky feeling.

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nupurtomar56 said...

very impressive article and very interesting way of explanation of hair shampoo,it also depend on hair to hair and cleaning of hair will help to make our hair more healthy and shine.
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