I got a couple of commercial 5 L porcelain ball mill jars and thought that I should test them before I committed my glazes to them, just to make sure that whatever casting residue that might come off initially would not contaminate my glazes.
I ran two different 5 L porcelain ball mill jars with 20 pounds alumina grinding balls and water for up to 13 hours. I change the water regularly, usually about every hour. Even after running this long, the water was still coming out a thin, opaque white liquid a little thinner than skim milk. This does not sound right to me since I thought the idea of a porcelain jar and alumina balls was to not leave any noticeable grinding residue in the glaze.
What do you think? Has anyone tried this?