Yeah, I thought so too. I had no idea that they were still charring bone for pigments used in acrylic colors. I had sort of thought it would be all petrochemical synthesized stuff, but apparently not. My knowledge of pigments is somewhat spotty, because I only pick up stuff randomly, but every now and then I think I should really get some book about this, because the kinds of pigments used in colors really make a difference in the properties and handling, even in modern colors.
I noticed this when I started using acrylics for the first time, and I didn't know a lot about the different kinds of colors (still don't but at least I've tried a little now), beyond looking at their hue, and then for example I wanted to paint white highlights at the end of picture, but I had bought a tube of Zinc White, and I didn't get why it wouldn't cover the colors beneath even if I didn't make it thin or anything when I had read that you could paint lighter over darker acrylic colors, but it turns out that naturally Zinc White (made with zinc oxide as pigment) is much more transparent, and you use it in glazes and such I think, whereas it is Titan White (which uses titanium dioxide as pigment) that is more opaque. I hadn't known that it would make such a huge difference what kind of white pigment it was. Cluelessly I had just gotten a tube of white acrylic paint and thought it would work. Or when I tried ultramarine blue, it was always more grainy and less soluble somehow than the other blue I had and so on.
Also even the same quality grade, some colors are much more dominant in any mixture compared to very similar color that is made from a different pigment, like with the two different kinds of whites.
And I didn't know about the different blacks either. I've read a bit today and apparently originally there was "Bone Black" and true "Ivory Black" which was made from burning real ivory and had a better color quality than just burning any animal bone because of its higher carbon content. These days Ivory Black can also be synthetic by mixing inorganic carbon black and calcium phosphate, so not all are made from animals anymore. There's also other fully synthetic ones, like Mars Black (from iron oxide), and other kinds of carbon blacks like Lamp Black is also carbon, but from burnt vegetable oil historically or petroleum and other stuff today, but it is less used because it dries slower in paint and becomes more brittle according to what I've read than Ivory Black... so apparently pigments are still tricky.
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I noticed this when I started using acrylics for the first time, and I didn't know a lot about the different kinds of colors (still don't but at least I've tried a little now), beyond looking at their hue, and then for example I wanted to paint white highlights at the end of picture, but I had bought a tube of Zinc White, and I didn't get why it wouldn't cover the colors beneath even if I didn't make it thin or anything when I had read that you could paint lighter over darker acrylic colors, but it turns out that naturally Zinc White (made with zinc oxide as pigment) is much more transparent, and you use it in glazes and such I think, whereas it is Titan White (which uses titanium dioxide as pigment) that is more opaque. I hadn't known that it would make such a huge difference what kind of white pigment it was. Cluelessly I had just gotten a tube of white acrylic paint and thought it would work. Or when I tried ultramarine blue, it was always more grainy and less soluble somehow than the other blue I had and so on.
Also even the same quality grade, some colors are much more dominant in any mixture compared to very similar color that is made from a different pigment, like with the two different kinds of whites.
And I didn't know about the different blacks either. I've read a bit today and apparently originally there was "Bone Black" and true "Ivory Black" which was made from burning real ivory and had a better color quality than just burning any animal bone because of its higher carbon content. These days Ivory Black can also be synthetic by mixing inorganic carbon black and calcium phosphate, so not all are made from animals anymore. There's also other fully synthetic ones, like Mars Black (from iron oxide), and other kinds of carbon blacks like Lamp Black is also carbon, but from burnt vegetable oil historically or petroleum and other stuff today, but it is less used because it dries slower in paint and becomes more brittle according to what I've read than Ivory Black... so apparently pigments are still tricky.