jesse hull on thu 31 mar 05
"Crystallines" can be a vague reference. I know of no
one that's gotten zinc-silicate MACROcrystals at that
low temp. range. I do not believe it possible,
really. I've fired as low as cone 4 with mediocre
results and cone 6 with a much better outcome. I
currently fire to 2325-2365F, but my heat rise is so
fast (300-500deg/hr.) that I don't measure with cones
anymore. My holds are usually located b/t 2060-
1820F, but I've never experienced significant growth
below that range. ^04 is, what, 1922F? So, your peak
is not going to allow much of a decline before you
drop out of the crystal growing range, and even at
1800F, your glaze is probably going to be moving
pretty fast. A short 4 hr. hold and you'd have ...a
really pretty glaze catcher, maybe.
Cone 6 is the lowest I'd recommend for the type of
crystals I'm referring to, and William Schran (Va.) is
the person to direct your question to in that arena.
John Tilton and I were recently featured in John
Britt's new book, in which I believe Britt discusses
aventurine crystallines - they are quite lovely
glazes, but again, not the "macro" type you may be
asking about (I think he may fire his higher, anyway).
This aesthetic is like a really intense iron saturate
glaze. Herbert Sanders writes of low fire aventurines
in his book, which I think is no longer printed. If
you don't own a copy and want to try the recipe, I can
post it for you...
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Fara Shimbo on fri 1 apr 05
I've seen recipes for low-fire crystalline glazes but these are
for chrome reds, not zinc-silicate glazes. (Although now that I
think about it, there might be some in Ceramic Spectrum by Robin
Fara Shimbo, Master Crystalliere, Certified Public Nuisance
Shimbo Pottery, PO Box 41, Hygiene, CO 80533 USA 718.210.3492
Crystalline-Ceramics.Info ShimboPottery.com Crystallieri.Org