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Keep in mind, Oxides are strong colorants, so a little bit goes a long way. In a solution you will probably only want about 2-8% or you will end up with black. Use a respirator or mask when handling the dry oxides.
Remember that using oxides like this will provide unpredictable, but sometimes beautiful results. Test! And Take Notes! (I had to throw that in because I am lousy at taking notes, but getting better. It definitely helps.)