You can measure to see. How? Wash a measured amount through a 200 mesh screen and note the amount of residue. These two show the oversize on a 200 mesh screen of 100 grams of glaze slurry. On the left: Unmilled. On the right: Milled 1 hour. Clearly it needs more than 1 hour in this mill. A factor here is the high percentage of silica in this recipe. And the fact that 295 rather than 400 mesh silica was used.
A method of grinding particles in ceramic powders and slurries. A porcelain vessel filled with porcelain pebbles tumbles and particles are ground between colliding pebbles.