Looking through the ingredient list of makeup products can often feel like looking through an organic chemistry textbook, but the ingredients can give lots of useful information about using the product. If you have a known allergy to a certain class of chemicals or know that an ingredient breaks you out, the ingredients list will tell you products to avoid (for instance many people can have an allergy to Bismuth Oxychloride, an ingredient often found in loose powder foundations like Bare Minerals). In addition, the ingredients list can tell you about the product’s compatibility with other products.
If you look at foundation, you’ll find two major types of ingredients: water and silicones. Silicones are polymers, or large repeating chains, of siloxanes, a compound that alternates between silicon and oxygen.
A siloxane is a functional group that contains a silicon-oxygen linkage. A large chain of siloxanes will form a silicone.
Knowing whether you have a silicone-based or water-based foundation can be important when choosing a primer to use with a foundation. If you try to put a water-based foundation over a silicone primer, you may find that the foundation pills. This is because the non-polar silicone primer forms a hydrophobic layer on the skin that repels polar water molecules. In other words, the silicone primer will form a silicone barrier on the skin that prevents the water-based foundation from absorbing properly, causing unevenness.
If you want to check if a foundation or primer is silicone or water based, look for silicones near the top of the ingredient list (ingredients higher in the list are present in a greater amount). Keep in mind that for a liquid foundation, water (or aqua as its often listed) is almost always the first ingredient, so you need to check further down the list. Silicone ingredients usually have -icone or siloxy in their name.
Lets take a look at the Tarte Rainforest of the Sea foundation ingredient list from Sephora’s website:
Water, glycerin, isododecane, cyclopentasiloxane, phenyl trimethicone, nylon-12, dipropylene glycol, caprylic/capric triglyceride, cyclohexasiloxane, SD Alcohol 40-B, aluminum starch octenylsuccinate, butylene glycol, cetyl PEG/PPG-10/1 dimethicone, magnesium sulfate, alumina, PEG-9 polydimethylsiloxyethyl dimethicone, silica, talc, iron oxides, sorbitan isostearate, stearalkonium hectorite, polyglyceryl-4 isostearate, hexyl laurate, aluminum hydroxide, stearic acid, caprylyl glycol, propylene carbonate, dimethicone, hydrogen dimethicone, phenoxyethanol, triethoxycaprylylsilane, tocopheryl acetate, 1,2-hexanediol, cocos nucifera (coconut) oil, algae extract, gardenia tahitensis flower extract, tocopherol.
The ingredients in bold all have either siloxane or -icone in their name and are fairly high in the ingredient list, indicating this is a silicone based foundation. Therefore, if you wanted to use the Tarte Rainforest of the Sea foundation, you would best pair it with a silicone based primer.
Looking at the ingredient labels can give you a lot of information to be a smarter consumer, and you don’t need to be a chemist to figure it out once you know what you’re looking for. Check out your products’ ingredient list.