there is much debate with ash glazing potters of to wash or not to wash. i am an ash washer. you can get away with not washing some softwoods, but hardwoods tend to go bad(changes the glaze, usually not for the better) in as little as a week which means you can only mix up what you need at a given time. washing also adds a bit more consistency to the end product because who knows what contaminents are in a batch of ash and those are certainly not going to be consistent.
here's a bit of a tutorial for anyone interested:
i pre-screen with a large mesh. don't forget your respirator! ash is definitely an irritant.
the culprits: most of this would float to the top anyways but its easier to get it out now. at least they're wearing gloves to handle the meat!
fill bucket with about 1/3 ash and top off with water.
mix and let settle, screen off all the floating chunks and crud. once its settled you'll be left with a nasty smelling liquid that looks like pee.
once settled pour off the old water, top off with fresh water and mix. wash, rinse, repeat until the water is clear and less foul smelling(hardwoods can be 4-5 times). i pour the ash into my clay drying racks to dry.
well, i'm off to a headstone carver to see if i can score some granite dust.
local materials rule!