Paul Lewing on mon 7 nov 05
on 11/7/05 9:02 AM, Brad Carter at BRADCARTER@AOL.COM wrote:
> My question is the last item in the mix--86.9 zircopax--seems way high. Can
that be correct?
I doubt it. I wouldn't even expect that mixture to fuse, much less melt.
>
> Question 2. I have a glaze that calls for Kingman Feldspar. Is that soda spar
or potash spar? Does anyone know a source for it? Any recommended
substitutes for it?
All of us here in the western US used to use Kingman all the time. We al
switched to Custer, and saw no difference. If you want an exact duplicate,
you'd have to do it on the molecular level, but Kingman and Custer are about
as alike as any two feldspars have ever been.
Paul Lewing, Seattle
Brad Carter on mon 7 nov 05
I am testing various glazes and have a few questions:
1. Glaze name: Alligator Black=A0 (see CM=A0 Sept 05 pp 69).=A0
7.6%=A0=A0=A0=A0 Barium Carb
18.5=A0=A0=A0=A0 Gertsey borate
6.5=A0=A0=A0=A0 =A0=A0=A0=A0 Talc
2.1=A0=A0=A0=A0 =A0=A0=A0=A0 Whiting
41.3 =A0=A0=A0=A0 Custer
24.0=A0=A0=A0=A0 Silica
add
6.8=A0=A0=A0=A0 =A0=A0=A0=A0 copper carb
8.7=A0=A0=A0=A0 =A0=A0=A0=A0 zinc oxide
86.9=A0=A0=A0=A0 zircopax
My question is the last item in the mix--86.9 zircopax--seems way high.=A0 C=
an=20
that be correct?
Question 2.=A0 I have a glaze that calls for Kingman Feldspar.=A0 Is that a=20=
soda=20
spar or potash spar?=A0 Does anyone know a source for it?=A0 Any recommended=
=20
substitutes for it?
Thanks for the help.
Brad Carter
Grass Valley, California
John Hesselberth on mon 7 nov 05
On Nov 7, 2005, at 12:02 PM, Brad Carter wrote:
> My question is the last item in the mix--86.9 zircopax--seems way
> high. Can
> that be correct?
>
> Question 2. I have a glaze that calls for Kingman Feldspar. Is
> that a soda
> spar or potash spar? Does anyone know a source for it? Any
> recommended
> substitutes for it?
Hi Brad,
Well, I suppose 86.9 could be correct--this is not really a glaze in
the ordinary sense. I would call it a surface treatment. As you can
tell from the photo on p 68 it is a pretty crusty surface. But the
only way to know for sure would be to ask the author. Even if the
Zircopax amount is a typo and it really is in the more normal range
of 5-15% this surface treatment would only be suitable on decorative
or sculptural work. It has way too little alumina and way too much
copper to be durable enough to use of functional work..
Kingman is a high potassium feldspar. The closest you will come with
feldspars commercially available in North America today would be
Custer or G-200. In many glazes you won't see the difference, but
some potters would give their eye teeth to have Kingman available again.
Regards,
John
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