John Britt on wed 20 feb 08
Tom,
I usually try not to commment so that others will give their experiences
but I am wondering what light reduction means? I think I got the best
color from 02 and R2. Both cycles had pretty good reduction soaks at peak.
Don't know if other had the same experience?
As for discussing recipes on clayart...I think that is what clayart is all
about! Limiting discussion is counterproductive. Glaze Free Trade rules!
Waiting to hear,
John Britt
Tom King on wed 20 feb 08
Hi Folks,
While people are talking purple I thought I would run this one by.
Last spring I mixed a 2500 g batch of Watral purple care of John Britts book.
Page 115 in my edition shows a rather different purple that is to my eyes a
nice warm mahogany-grape satin matt.
Custer 40
silica 25
kaolin 5
Dolomite 10
Talc 10
Gerstley Borate 10
Colorants:
2 % Cobalt carb.
5 % Manganese dioxide
Cone 10 oxidizing
Result was a very pastel light blue-lavender.
There was no deep mysterious anything.
Presuming I erred, I remixed a 500 g batch for the next firing.
Cone 10 light reduction. Same result.
It seems like 2 % cobalt should at least be dark blue, and 5% MnO2 should
yield a good brown. so I don't know where the color went!
CoCO3 pink fluffy, right?
MnO2 Heavy black powder? Yes I got powdered manganese.
(Please ...the above two lines were levity.)
On Snow Porcelain and white stoneware.
Has anyone tried this glaze? with what result?
Any thoughts on probable reasons for the loss of color?
And not least... Thank you John for granting the freedom to openly discuss
glazes published in your Great book.
Spring comes soon,
Be Well,
Tom King
Paul Gruner on thu 21 feb 08
That's interesting. Or maybe I should say "puzzling."
I had the impression that manganese would be purple in an alkaline glaze,
but this glaze more calcium and magnesium than alkalines. I was assuming
that either calium or magnesium would make the manganese turn brown. But
maybe it's more a matter of getting the silica and alumina levels just
right.
Another bit of data before I start testing manganese glazes. Thanks for
posting it.
-Paul Gruner
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