Crystaline glaze "problem?"
 

Hi All,

I just did my first crystalline glaze firing (glaze formula and firing
schedule below) and for the most part I am very happy with the results I
got. The one problem is that the glaze that settled into the bottoms of the
bowels is not smooth or glossy like the sides. In fact it almost looks
charred with an abundance of very black, small needle like crystalline
forms. No glassy appearance at all in the bottoms.

Formula
Ferro Frit 3110 50
Zinc Oxide 28
Flint 22
Bentonite 3
Manganese Dioxide 2
Cobalt Carb. 0.5

Firing Schedule
Rate Temp F Hold Time
200Hr 800
150Hr 1250
300Hr 2100
100Hr 2282 12 Min
Quick Cool 2012 1 Hr 22 Min.
150Hr 2066 2 Hours
Shutdown and cool normally

Any input is welcome.
Thanks
Larry

I'm not sure why it's doing what it's doing, but you could apply the glaze a bit
thinner, and maybe cut down on the pooling that is causing it. All crystalline
glazes are runny, so tend to get thick drops or pools at the bottom of the
forms. If the sides weren't glossy, I'd say it was underfired, but that doesn't
seem to be the issue.
:
Brad Sondahl--
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