by Right Brain on February 28, 2009 · 3 comments
Stephanie Seeks Clarification: Is there a scientific reason why shampoos are usually clear or close to clear and conditioners usually are not?
The Right Brain Clears Things Up:
Great question! Shampoos are composed mainly of water and surfactants. (If surfactants sounds to technical, you can call them detergents. If detergents reminds you too much of laundry, you can call them foaming thingies. Whatever.)
Anyway the foaming thingies, uh I mean the surfactants, are soluble in water so the shampoo is clear. It’s like putting salt into water – all the salt dissolves and you can still see through the water.
Conditioners on the other hand are composed mainly of water and conditioning agents. Most conditioning agents are not compatible with water (they won’t dissolve in it). So, to make a conditioner you have to create a special type of mixture called an emulsion. Emulsions are just small particles of oils suspended in water. (Think about the kind of 2-layer oil and vinegar salad dressing that you have to shake before using. That’s a simple emulsion.) In an emulsion, the light passing through the product is scattered when it hits all those tiny suspended oil particles. That light scattering makes the conditioner look opaque.
By the way, you can make a clear conditioner by using water soluble conditioners or a special type of emulsion known as a microemulsion. But there’s never been a successful one on the market because people don’t believe they work! (Does anyone remember the original Clean and Clear from the late 80s? They had a clear hair conditioner. Ahh, sweet memories.)