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Left: GA6-C rutile blue glaze on a brown stoneware. The 4% ceramic rutile powder gives the blue variegated effect. Right: We ball-milled our granular rutile and then screened it down to 325 mesh and put that into the same glaze. The results are the same. So if any of your rutile glazes ever lose this effect with a new supply of the material the cause could be that it has not been milled sufficiently fine. Finer rutile powders are browner in color.
Yes, the granular and powdered grades of pure rutile are the same material. But, for producers, the milling process it is very difficult because the raw mineral is so hard. Commercial ceramic grade powder is minus 325 mesh, the companies doing this obviously have very good grinding equipment. They also have patience because even in this efficient porcelain ball mill, 90 minutes was only enough to get 50% to minus 325 mesh! The color of the powder is a good indication of its quality, the finer the grind the lighter tan it will be. That means you can use the color to gauge the mesh size. And, if you have a ball mill you can milled it more if needed.
Materials |
Ceramic Rutile
Rutile mineral ground to a very fine particle size (e.g. 325 mesh) contributes titanium and iron that colors and variegates ceramic glazes. |
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Materials |
Rutile
A raw TiO2-containing mineral used in ceramics to color and variegate glaze surfaces. |
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