As the rain seemed to have stopped for a while I made the most of being able to work outside preparing wood (splitting by hand as my wood splitter has frustratingly burnt out its electrics) and rocks for my next batches of glazes.
The kiln was lit for a slow bisque. Muscles tensed, I approached the steel mortar and pestle with buckets of calcined rock.
I break up the rocks into manageable sizes with a hammer before calcining them in my gas test kiln. Then, using this mortar and a 1 1/2 inch diameter steel pestle, I crush them down to 8 mesh (around 2.5mm max diameter).
Calcining works best on igneous rocks with large crystals like Dartmoor granite. Unfortunately for my arms I had fine rocks such as Arthurs Seat basalt from Edinburgh.....
.... a triassic sandstone from Martley in Worcestershire, Pentland felsite and a metamorphosed granite from the Malverns that has separated into thick swirls of quartz, feldspar and mica.
This collection of buckets took me 4 hours and is now ready for the ball mill.
3 hours of milling and the grit is reduced to a fine dust that will readily pass through a 60 mesh seive, with about 90% through 100 mesh. I used to mill finer but find that this slightly coarser grade gives good results.
The red lidded jar is 2/3 full of hard alumina balls, which tumble as they rotate, crushing the rock. I am milling most of the rocks dry....
...though I mill quartz wet for the best results, and to keep the dust down as I need this very fine. Here it is settling out (which takes about 24 hours) before it can be slopped onto a plaster batt to dry.
For some reason I am unable to reply to comments on my post so......
Hi William. Don't mind at all. You can certainly use it to make a glaze. Try using it to replace the feldpar in one of your usual glazes or do a lineblend adding whiting and some clay. Good luck!
