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stupid (heck no!) crystalline glaze questions

updated tue 2 mar 04


Fara Shimbo on mon 1 mar 04

Hi, Kim Marie,

Your questions certainly aren't stupid! Someone once asked
me if a male dog would follow a female dog in heat. Now *that*
was a stupid question!

> If I don't put any colorant in, will I have a nice clear glaze and
still be able to see the crystals?

Yes. Depending on the glaze they'll either be against a
transparent ground or a white ground. In the latter case
they'll usually be someone golden colored but still clearly

> With the zinc present in these tests, the only colorants mentioned
for use
> are nickel and copper. Could I use cobalt? Are small % of stains
ever used with crystals?

I use every colorant there is with crystalline glazes, including
rare earths, silver and gold, and even chrome which can give a gorgeous
brown with golden-green crystals if you mix it fresh and fire it fast.
Stains, in my experience, don't always give results any better than
the oxides and carbonates (for example, Mason 6450 Praseodymium yellow
comes out the lime green of praseodymium rather than the yellow of
the stain, so you might as well use praseo).
You'll find some colorant tests here:

These were done at cone 9 but they work at cone 6 too.

> Would I use these at approximately the same thickness as my other glazes
> which I usually dip pieces in?

No. Crystalline glazes need to be THICK, especially at the top.
They run like fury, and if you haven't discovered this already,
drip-catchers are necessary. A layer of glaze about 2 mm thick at
the top, and 1 mm at the bottom, is what I normally put. On a tile
it's possible to put too much glaze, but on a pot, you can't. Slather
that stuff on!

Hope this helps,

Fara Shimbo, Master Crystalliere, Certified Public Nuisance
Shimbo Pottery, PO Box 41, Hygiene, CO 80533 USA 720.272.0442
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