Rod Wuetherick on sat 11 jun 05
You also write: "we are very happy with the gold crystal glazes. they do
not happen every day." I would have to argue with this, (unless I have
read something wrong again) because, fortunately, they can and do happen
everyday, if you have the right recipe and firing protocols.
John,
Are we talking about the gold crystals that some love and some can't stand?
I'm assuming these gold crystals are simply pyroxene crystals - hate em.
Some people add magnesium carbonate in small amounts to ambers, etc. to get
them. Fire slow with a bit of MgCo3 or a spar like Dolomite, etc and you can
get more of them gold crystals than you can swing a cat at.
I haven't studied them at all as I personally don't find the effect
interesting. I believe glazes containing Mg that have a viscosity like that
of tenmoku glazes seem to promote development of pyroxene crystals very
easily.
Some have said that reduction helps though I don't think that has anything
to do with it. Perhaps when someone try's once with a little reduction and
another time reducing heavily what is really happening is that the firing is
longer because of the heavy reduction, giving the crystals time to develop.
I could be wrong but I think if you added .5% of MgCo3 to any tenmoku glaze
and fired slowly in oxidation you would get pyroxene crystals.
peace,
Rod
John Britt on sat 11 jun 05
ROd,
No, they are not pyroxene crystals. They are iron crystals. Very fluid
glazes with high percentages of iron that are soaked during cooling, like
a standard crystalline glaze firing cycle, will grow iron crystals. (No
zinc or magnesium oxide)Some are called Aventurine and others Goldstone.
Try it out for your self. They are wonderful!
John Britt
www.johnbrittpottery.com
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