Mica is a name given to a group of silicate minerals, which form distinct sheets and flakes. These are very thin and light, and are most commonly found in schist and granite, giving the rock its shiny, sparkly appearance. It’s this sparkle that makes the mineral so attractive to the cosmetic industry. Although mica occurs naturally, it is very expensive to mine and the cosmetic grade micas, which are used in make up, are often synthetically produced in the lab. Keep this in mind when making claims of natural products!
Synthetically produced mica has the same crystal structure as natural occurring mica in rocks – a very thin, transparent two-dimensional sheet structure. For example, Geotech in the Netherlands, is one such company, which produces synthetic mica for the cosmetic industry. The mica used in cosmetics is usually transparent and colourless, so to achieve the many hues of colours, it has to be coloured with pigments or dyes.
How to use mica in soap making? The general rule of thumb is to use one teaspoon of mica in 500 g of soap. A trick I learned from Soap Queen, is to disperse the mica in a little lightweight oil – I use rice bran oil – and mix it with a electric mini-mixer until you have a smooth paste, and add this to your soap at light trace.
I have a love and hate relationship with micas in soap making. I love the bright, sparkly, and often rich shades, and they are very easy to work with. They don’t clump and don’t speckle the soap. But unfortunately, they are also very fickle in cold process soap, due to particular colourants, pigments, or dyes used to colour the micas, which makes them unstable in the high pH environment of cold process soap making. In other words, you never know what you get. Some micas stay true to their colour, but others morph into other colours, most often grey and brown, and some disappear altogether. The only way to be certain if the mica is colour stable is by testing.
Over the next few weeks, I’ll be testing all the micas from Pure Nature in cold process soap and will be posting the results here. And because I also want to have some fun while I’m playing with colour, I’ll be creating some colourful tutorials for you to try out!