Hello, I need some advice on how to grind cosmetic iron oxide pigments and titanium dioxide to be incorporated into premade nail polish suspension bases. The problem I'm having is that my pigments are not grinding down fine enough to mix properly into the suspension base, and they end up separating. I tried a coffee grinder, grinding by hand with a mortar and pestle, and I'm sure it's not my suspension base since it has a thicker viscosity. I see people using 95% - 99.9% isopropyl alcohol to grind down the pigment. However I'm worried about the water content of the isopropyl alcohol and its effect in the premade base formula. Is that recommended? Wouldn't the water content in the isopropyl alcohol mess with the formula? What would you guys suggest to grind down the pigments?