Lili Krakowski on sat 6 jan 07
Hermann Seger, of blessed memory, invented the pyrometric cone. It was named
for him, the Seger cone. It measures temperature, and is still used in
Germany. The Brits modified/adapted it to the Stafforshire cone, and I do
not know if and if so how it differs from the Seger cone.
The Edward Orton Jr developed the Orton cone which measures WORK.
The difference is that as you know from cooking and baking WORK is a
relationship of time and heat. You cannot bake a roast faster by turning
the heat up to 500 degrees and cooking it for 1/2 hour, rather than the 350
degrees and one hour the cookbook calls for.
As the Orton cone is a US innovation, I expect most recipes in ClayArt
Archives are based on Orton cones/listed by Orton cones.
So if the temp you want is 1200 degrees, I assume Centigrade, (2192F) you
are at a British c 6, a Seger cone 6a, BUT between c.4 and c.5 Orton cone.
And Orton c.5 is 1205C/2201F. An Orton c. 6 is 1230C/2246F, and the British
c.7 is the equivalent. (This dazzling info from the (truly, honestly)
dazzling THE POTTER's BOOK OF GLAZE RECIPES, by Emmanuel Cooper. The term
"British" cone is his, I take it to meant Staffordshire, but am not sure.
(Once one learns to spell Staffordshire it ain't no obstacle)
It seems to me you have a couple of options. You look for c.4-5 glazes in
the Archives, or you test what is listed at c.6.
(I know that all the Hobart Cowles glazes work at c.6 as well as c.5.) If
the c.4 glazes run too much at c.6 add clay at 5% increments.
Now as to your frit problem. Just about everybody in the US turned to frits
because of all the troubles with Gerstley Borate and Colemanite. So I
suggest that, as the most commonly "converted to" is Frit 3124, you test GB
and C in recipes calling for Frit 3124.
Lili Krakowski
Be of good courage
Ron Roy on sun 7 jan 07
Hi Lili,
Used to be that 3124 was the usual frit potters used. That was because it
was the cheapest and we used to have the notion that all frits were more of
less the same.
The problem is - 3124 has only 13% boron - and what we usually buy frits
for is the boron. Frit 3134 has become the more popular frit because it has
23% boron - so you are getting almost twice the boron for just a bit more
per bag.
Thats not the end of the story - 3134 has no alumina in it - and 3124 has
10% - so if you use 3134 you can get more raw clay in the recipe - which
usually is a help.
Notice I did not say 3124 was never a good idea - but any solution using it
will cost more and you will have to use more - and perhaps have to deal
with settling problems.
Choosing the right frit for the job involves knowing the analysis of the
frits available to you. Best not to use frits that you cannot get the
analysis for.
RR
>Now as to your frit problem. Just about everybody in the US turned to frits
>because of all the troubles with Gerstley Borate and Colemanite. So I
>suggest that, as the most commonly "converted to" is Frit 3124, you test GB
>and C in recipes calling for Frit 3124.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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