Randy McCall on sat 10 dec 05
I am trying to come up with an alkaline turquoise glaze for Cone 6.
Chappell has a Cone 5 that I have adjusted. Would someone look at this
glaze to see if there may be any problems.
Will be using Highwater Ellen Cone 6 Buff clay.
Feldspar-Custer 33.5
Frit--Ferro 3195 25.3
Silica 19.7
Wollastonite 5.6
Gerstley Borate 6.5
OM4 9.4
Copper Carb 3.0
Randy
Pottery Web Site
members.tripod.com/~McCallJ/index.html
South Carolina
John Hesselberth on sun 11 dec 05
On Dec 10, 2005, at 10:05 AM, Randy McCall wrote:
> I am trying to come up with an alkaline turquoise glaze for Cone 6.
>
> Chappell has a Cone 5 that I have adjusted. Would someone look at
> this
> glaze to see if there may be any problems.
Hi Randy,
Ahhh, the search for the elusive turquoise. Just some observations.
You may be a little light on alkalis to get turquoise--hard to tell
without testing. Most attempts I've seen at turquoise use Neph Sy
instead of a potassium feldspar. You might try it both ways. Neph Sy
(at equal weights) will give you more total alkalis as well as more
sodium. My biggest question about getting the color though is all
the other things you have done. High silica and alumina--presumably
to try to overcome the usual problem with alkaline glazes--crazing.
Then you have put in a lot of boron--presumably to try to get it melt
with all that silica and alumina. The amount of boron you are using
is more typical of a cone 1 or 2 glaze.
It's worth a try, but don't get your hopes up too high. One change I
would make if I were going to try this unity formula is to get rid of
the Gerstley Borate. Why use a highly variable material of
questionable future availability when developing a new glaze? Good
luck.
Regards,
John
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