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fwd: ^5-6 problemfrom clayarter

updated fri 30 mar 07


mel jacobson on thu 29 mar 07

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>I am a potter in Half Moon Bay, CA (retired and operating a single
>man pottery) firing cone 6 oxidation after 17 years cone 10
>reduction in a coop in San Francisco. The building in SF is being
>torn down and that pottery is defunct. Before that I taught ceramics
>in HS for 10 years and fired cone 6 ox (I was a reformed English
>teacher before that.)
>Before the studio in SF closed I mixed the following glaze batch and
>got a variegated greenish celedon that ran and pooled.
>Kona F4 --38
>Whiting -- 14
>Zn O --12
>Ball clay-- 6
>Silica ------30
>Cu Co3 --.5
>In the second 5,000 gram batch I substituted Del Monte for the F4
>and added 100 grams of calcined epk to control the running.What I
>got was a less translucent green, orange peel result. Inexplicably
>some very small parts of the fired pots were smooth and clear like
>the original. I was sorely disappointed. I took a sample of the
>glaze and added a spoon of neph sye. I fired that at cone 5 with an
>hour soak. The result was shinier and only slightly peely, but not
>like the original. Did the change from the F4 and or the 100 grams
>of epk cause the change?
>Better, can you advise on how to get the translucent celedon look
>back? I Just tested your Ron's liner glaze from Pottery mag which
>came out perfectly in cone 5.
>Denis Rauchman
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from: mel/

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