What is dimethicone? Dimethicone is a non-volatile oil soluble silicone you can add to your hair and body care ingredients.
In body care products, it works as a barrier ingredient, emollient, lubricant, carrier/diluent detackifier, and and skin protectant (one of three approved by the FDA). You can use it in products as diverse as body lotion and lip balm to offer shine, glide, and protection from the elements.
In hair care, it improves wet and dry combing, helps with shine, improves hair feel (softness), reduces static charge, and works as a humidity resistor. And in colour cosmetics, like foundations, it is a lubricant, spreading agent, emollient, and diluent/carrier ingredient.
Is there anything dimethicone can't do?
Yep, it can't create world peace. Although if everyone had shiny, soft, manageable hair, perhaps the world would be a nicer place and people might get along better...but I digress.
How does it perform such miracles?
Dimethicone tends to migrate to the surface of your hair or skin, forming a nice film that not only protects your skin, but keeps all the good stuff you've put into your lotion or conditioner to your skin or hair.
Dimethicone is rated by c.s. or centistrokes. The higher the c.s., the thicker you'll find your dimethicone. 350 c.s. is considered as thick as mineral oil (so thicker than shampoo, but not as thick as ketchup), whereas dimethicone 1000 c.s. is going to be as thick as motor oil (so thicker than ketchup, but not as thick as molasses). So why should you care about the centistrokes? The lower the centistrokes, the quicker surface coverage...so if you have the 350 c.s., it is going to spread quicker than the 1000 c.s.
As an aside, these descriptions of viscosity are given by the manufacturers of dimethicone, and I think they're not great. Really, do I want to use the words "motor oil" when I'm trying to tell you about this wonderful product that will bring shine and manageability to your hair? I know I'm picturing my hair dripping with grease...not a nice image.
So why use the 1000 c.s. (like I do in my hair care products)? Because it will form a nicer, more long lasting barrier for hair in humidity, for instance. I like to use the 350 c.s. in body care products; 1000 c.s. in hair care products.
It is non-volatile over 5 c.s., meaning it won't evaporate from your skin or hair like cyclomethicone will.
Given this giant list of things dimethicone can do...well, I think we're going to need a little more than one post to discuss the awesome power of this silicone...
The quick summary - dimethicone is not suitable for water only products, like toners, but works well in lotions, surfactant systems, conditioners, and other surfactant or emulsified products. Use at up to 5% - although I like 2 to 3% - in these systems.