Grinding Cosmetic Pigment Oxides

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? 

Comments

  • You should be able to purchase your inorganic pigments as small enough particle sizes for incorporating into your mixture.
    What I have found, if ever I need to mix inorganic pigments into bases (granted, they're solid suspensions that result and not liquid) is to mix your pigment into a small portion of the base you're aiming to use and then incorporate that into the rest of the base.
    That said, they should simply mix with reasonable ease. Typically nail polishes have a 'mix well before use' type of clause anyway so some settling of pigment
    isn't unheard of.
  • That's what I've been doing, but i'm still not able to ground it fine enough. But thank you for taking the time to respond back.
  • That's what I've been doing, but i'm still not able to ground it fine enough. But thank you for taking the time to respond back.
    Very welcome. I'd be tempted to find a supplier who would give you a fine enough powder to incorporate without issue.
  • No matter how much grinding you do, pigments are prone to agglomeration - it sounds to me like your problem might be dispersion rather than particle size. Without specialist equipment, it can be challenging in the lab to properly disperse pigments. Looking up paint pigment dispersion techniques might be a good place to start - nail polish and industrial paint technologies are more similar than you may think.
  • I recommend purchasing pre-dispersed and milled colorants for use in your base. You can only break down the particle size to a certain point with the methods you have available. To get a finer particle size typically a mill is used.
  • You would probably need to buy a glass muller for an artists supply shop and grind the pigments yourself in a liquid base. Artists tend to use oils, IPA may evaporate too quickly to do this effectively. 

    So, may be better to buy pre-dispersed pigments.
  • Thank you guys. 
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