As we discussed on the previous page, silicone polymers such as dimethicone help create protective barriers on the skin. In the 1980s, researchers discovered how to create elastomers for the skin care industry. In terms of sebum control, this discovery added the mattifying component consumers desired because the silicone elastomers absorb multiple types of oil and give the skin a smooth, powdery feel.
Elastomers are formed when a catalyst activates a cross-linker, or a reactive chemical, creating connections between linear polymers. When you look at a linear polymer, it can have reactive sites along the chain. Cross-linkers connect linear polymers and create a new substance -- the elastomer -- with both a different physical and chemical makeup. The difference between the linear polymers and the elastomers is that, when solvents are introduced as ingredients in the product, linear polymers become soluble, whereas elastomers swell or expand.
The amount a silicone elastomer can expand depends on the number of cross-links. Fewer cross-links create a softer product with great expanding capabilities. More cross-links produce a harder product that doesn't expand as much when in the presence of a solvent. The more the elastomer expands, the more of a smooth and powdery feeling it should give your skin. This is why silicone elastomers -- moreso than silicone polymers -- work well as mattifying agents to give your skin a smooth, even appearance that makes a good base for applying makeup.
Also, when a substance called cyclopentasiloxane is included in the silicone elastomer, it helps to dissolve sebum and also to improve activity between the sebum and the elastomer, which can make the mattifying effect last longer [source: Starch].
Now that you know a little more about the chemistry behind the product, let's look at the different types of mattifying products on the market.