Wednesday, August 26, 2015

Designing your products as a line: Shampoo - how does it work?

The post, Should we design our recipes as lines of products?, put forth the idea that maybe we should be consider what we use together when we are making our products. Can we leave ingredients out or reduce the concentration of ingredients when we know what might be coming next? To that end, let's take a look at the first product most of us use when we're washing our hair - shampoo!

How does shampoo remove sebum, dir, skin cells, and so on from our hair?

The main ingredients in a shampoo are the foamy, bubbly, and lathery ingredients we call surfactants. Surfactants are wetting agents that lower the surface tension of a liquid, allowing easier spreading, and lower the interfacial tension between two liquids. (In other words, a surfactant makes it possible to mix oil and water or for lathery things to remove oil or dirt from your skin or clothes.) (From Wikipedia.)

Surfactants have a hydrophilic (or water-loving) head and a lipophilic (or fat-loving) tail. The hydrophilic head clings onto watery stuff - say the water phase of our lotion - and the lipophilic tail creates a ball around the oily stuff - the oil phase of our lotion.

When it comes to making a shampoo, our focus will be the lathery, foamy types of surfactants or surfactants that exhibit detergency - meaning something that wets and solubilizes oils, soils, and proteins, and removes them from surfaces, clothes, and people. They tend to be bubbly, foamy, and lathery. 

Yes, the emulsifiers we use like Polawax or BTMS are surfactants! 

We know that surfactants lower surface tension, 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
Join me tomorrow as we take a look at what ingredients we might find in a shampoo!

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Kim said...

Since emulsifiers are also surfactants, can they be used to cleanse hair?

Susan Barclay-Nichols said...

Kind of. As you can see in the post, there are cleansing mechanisms unique to detergents that you don't find in all emulsifiers. You will get the emulsification of oils, which is how using a conditioner as a shampoo works.