Often times adding clays or powders to lotions may make them harder to sterilize. I suggest you sterilize the powder or pigment before adding them you formations that contain water. It is quite simple and straightforward. copyright diycosmetics.com 2017
Ref: Martindale Pharmacopoeia
- Completely remove all moisture from the powder by putting it into at over on low heat (100 degree C). Do this for about 15 minutes.
- Bake the powder at 160 degrees C for at least one hour.
- Decant into an sterile container till ready to use.