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 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!
I’v been using water to mix my micas for cold and hot process soaps, and they’ve been coming out amazing. I don’t know about anyone else, but when I use oil- even a very lightweight oil- my soaps end up bleeding. Not matter the measurements I use..
Hi BreaMichelle! The reason we pre-mix micas, or most colourants for that matter, in a medium is to prevent speckling of colour in the soap. This is when the colour hasn’t been evenly dispersed throughout the soap. Micas don’t dissolve, but are rather suspended through the soap. If you were to look at the soap under a microscope you’d actually see tiny dots of colour. When a colour dissolves, for example when using dyes, the whole soap is dyed, which under the microscope you would see coloured soap, rather than white soap with coloured dots. Now micas don’t, or can’t, bleed, but what can bleed are the dyes used to colour the micas. If the mica has been coloured with soluble dyes, which you will recognise in the INCI as Blue 2 or Red 44 for example, then yes, your mica can bleed. But this will happen regardless if pre-mixed in oils or water. On the other hand, if your micas are coloured using mineral pigments, such as iron oxides, then the soap won’t bleed, because mineral pigments, like mica, doesn’t dissolve. I hope that makes sense!
Around how much by volume is there for 10g of micas/oxides? I wanna get my hands on these but if they’re only enough to colour a few batches of soap I feel that they aren’t worth it!
Hi Laura! 10g will colour quite a few batches of soap, but I haven’t counted how many teaspoons 10g will give (1 teaspoon will colour 500 g of soap). A more economical alternative, and my personal preference, are soap pigments. They are slightly more expensive, but they will last you for ages. A tiny little 0.15 cc scoop of pigment will colour 500g of soap. Plus you only need the three main colours, red, yellow and blue, and can mix all the other colours from these three. You can check out my blog post on soap pigments here https://inmysoappot.co.nz/2017/04/18/how-to-use-soap-pigments/