A shimmery body oil is the perfect summer accessory! You can achieve a photo-perfect glow on your skin by massaging in a bit of oil loaded with mica. It's a simple concept and easy to make.
Mica settles
There are a couple of issues with your common shimmer body oil. The first is usually obvious after a day or two: since mica is dispersible but not soluble, it will settle out of any liquid with time. Therefore the liquid needs either a thickening agent or suspending agent to keep it 'afloat'. You can choose to ignore the settling issue and just shake up your oil before use, but we like to solve formulating problems so we're choosing to rather go the hard route on this one!
We solve this problem by adding a rather strange addition considering this is a purely anhydrous formulation: an emulsifier. You want something that thickens oils, and emulsifiers do just that as they have inherent thickening properties!
You may ask, why don't we rather use a butter or fatty acid, as those are typical viscosity modifiers. The answer is that fatty acids (which are found in butters) tend to settle out of liquid oils as well, especially if there are temperature fluctuations. Have you ever had a grainy shea butter? Or a coconut oil that liquefies and solidifies whenever the temperature changes? That is due to the fatty acid content. Fatty acids have different melting and solidifying temperatures compared to liquid oils, and it's quite a fine balance to get consistencies right, which is why body butters are actually quite technical to make.
So rather than struggle with fatty acids, we're simply going to use an emulsifier. It's oil soluble, has its own thickening properties and isn't a fatty acid trying to fight back. problem solved!
