|Monthly Tech-Tip |
This 1000 ml 24 hour sedimentation test compares Plainsman A2 ball clay ground to 10 mesh (left) with that same material ball milled for an hour (right). The 10 mesh designation is a little misleading, those are agglomerates. When it is put into water many of those particles break down releasing the ultimates and it does suspend fairly well. But after 24 hours, not only has it settled completely from the upper section but there is a heavy sediment on the bottom. But with the milled material it has only settled slightly and there is no sediment on the bottom. Clearly, using an industrial attrition ball mill this material could be made completely colloidal.
Utlimate particles of ceramic materials are finer than can be measured even on a 325 mesh screen. These particles are the key players in the physical presence of the material.
In ceramics some clays of are of such exceedingly small particle sizes that they can stay in suspension in water indefinitely. But unlike common colloids, clays have a secret weapon.
A method of grinding particles in ceramic powders and slurries. A porcelain, metal or rubber vessel filled with pebbles tumbles and particles are ground between colliding pebbles.
Ultimate Particle Size Distribution
A fine particled highly plastic secondary clay used mainly to impart plasticity to clay and porcelain bodies and to suspend glaze, slips and engobe slurries.