Martin Howard on tue 22 dec 98
In my search for local, free, useful glaze materials, I have found a
supply of stone dust, a lovely, disgusting gunge, from a diamond saw
used by the local firm of monumental masons. As my wife and I are the
Burials Committee of our Quaker Meeting, we have a good relationship
with this firm :-)
The gunge I now have is stated by the firm to be 90% granite - indian
black, south african dark grey, and chinese black. The rest, 10%, is
probably made up of carara marble and a little york stone.
Can any ClayArt specialists give me any detailed figures of the chemical
constituents, formulae, of any of these materials? I could then put the
figures in as a new RM in David Hewitt's excellent Excel Glaze Workbook,
and create new glazes. Otherwise I must just try it and see. It might be
similar to Neph. Syenite and therefore useful for lowering the glaze
cone (I work at 02-1) for ash glazes.
Any help will be appreciated.
Martin Howard
araneajo@gn.apc.org
Jim Bozeman on wed 23 dec 98
Martin, I too use granite powder as part of my glaze composition. A
friend of mine cuts granite for a living and I get the powder. I too
wondered what the composition for the granite was. I saw a book
somewhere that touched on the composition of granite; I 'm going by
memory here; as I recall it is composed 70% of silica. In my recipe I
use 24% granite powder. The rest is feldspar, calcined sea shells and
wood ashes. I fire it to cone 10. Hope some of this helps, Jim Bozeman
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