Subject line notwithstanding, this has to do with enamelling. I purchase all my enamels already ground to 80 grit or higher and simply wash them to remove impurities, small particles, etc. What is the purpose of grinding enamels further in a mortar & pestle?
ummm…no pupose that I, my books or my past professor know of.
Okay, there is one reason I can think of. If you want to paint
it on using oil or binders the finer the enamel the smoother it
flows on and looks less grainy in the finished product. But that
is the only reason I know of.
Hope this helps