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ohata red, cone 6, reduction

updated fri 11 aug 00


Jeff Lawrence on wed 9 aug 00

Hello Alisa,

I tested the Ohata Red that Marcia posted, using the following
firing regimen:
pilot burners until whole kiln was at about 300 degree F
about 200-250 degree/hour to 1500
reduced .75 on oxyprobe and continued 200-250 deg/hour
until cone 6 dropped
soaked at temp (about 2150 deg F on my probes) for about two hours
cooled for a several hours with pilots on
relit burners at about 1000 deg F and held it there for an hour
shut off gas, air and damper

The appearance was really good on a locally made cone 6 white stoneware:
reddish brown with tomato colored flecks interspersed with black specks.
Same glaze with crocus martis instead of ROI was purpler; same glaze with
spanish iron oxide was browner. THe contrast between the different browns
was particularly pleasant.

There was substantial delayed crazing (as with Marcia's mat white); I didn't
care for the overlap of Ohata over white -- swampy greenish brown.

On a native brown clay that bleeds brown specks, the results were also good,
with even more flecks of color.

Two other results from the same firing --

RR Floating blue gave an olive green; where it overlapped Marcia's mat white
I got gaudy blue drips into the green.

Marcia's Midnight Blue was deep blue as advertised; where it overlapped
Marcia's mat white, there were areas where it formed a gold lacy pattern
atop the blue that was very handsome. As if the rutile had marbled itself on
the surface and froze there. An effect to pursue ...

I was reading in Hamer that under reduction, iron can be substituted as a
flux part for part for lead oxide, which surprised me.

Jeff Lawrence ph. 505-753-5913
Sun Dagger Design fx. 505-753-8074
18496 US HWY 285/84
Espanola, NM 87532