Craig Martell on sat 18 jan 97
Hi copper red enthusiasts: I talked to Jim Robinson today about the demise
of Kingman feldspar which happened a good 15 yrs ago. It seems that folks
using Kingman noticed that their glazes were stiffening up quite a bit and it
was suspected by some that the alkaline flux was present in lesser quanities
in the spar. Jim got an analysis from the mine that didn't appear too
different from earlier analyses. He did some fusion buttons of Kingman and
found a drastic change in the material. Instead of a pearly white fusion, he
got a dirty grey looking button with much less fusion than the analysis
promised and less than previous fusions he had done with Kingman when it was
a good material. It indeed appeared that the % of potassium had dropped and
there was an increase in a rather dirty, impure form of silica. That was it
for Kingman. Nice stuff, but it's gone.
If you have a copper red formula that calls for Kingman, Jim suggests that
you put the receipe into the seger formula and replace the Kingman with
Custer. He says that Custer, being high in potash and low in calcium will
produce good reds much like Kingman did. Custer is higher in silica though
so you need to recalculate the glaze. I think Custer has about 7 moles of
silica to 1 alkaline flux.
I hope this is of some help, Craig Martell-Oregon
George Mackie on sun 19 jan 97
I have 50lb of Kingman dating back to about 1975 which i dont need as I
switched to eartehenware so if anyone is totally desperate
enough.....George
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