For small jobs I use a muddler in an cut glass old fashioned glass [see bar supplies] for slightly larger jobs I use spice grinders [piggly wiggly sells low end spices in these for a buck] i usually throw the spices away because they are crap the grinders screw off the jar and have 4 different settings. plastic but I haven't broken one yet. Next step up is a power coffee grinder again adjustable from perk to expresso powder. limited space about 1/3 cup at a time but it is very fast [and noisey]. I was a chemist and over the years various have 'followed me home' the stabdard white coors at 3 1/2" works best for me. The bottom of the mortar and the face of the pestle are unglazed and you can grind until happy. BTW those groved mortars from Japan willl not grind finer than the depth of the groves.