Crystaline glaze "problem?"

Jul 02, 2003 1 Replies
L

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


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B

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-- For original art, music, pottery, and literature, visit my homepage

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