[Clayart] 5 hour firing

Bonnie Staffel bstaffel at chartermi.net
Wed Dec 23 20:58:38 EST 2015


I have to chime in about my experiences with firing reduction in an electric
kiln for copper reds. I found a reference to such activity through an
article in an old Ceramics Monthly written by Carleton Ball. It was
reduction on cooling. I adopted this method with a simple Cone 04 Frit based
3134 three or four ingredient glaze. It was a beautiful White glossy glaze.
First time was with moth balls tossed into the peep hole. Had to leave the
studio while it burned, however I didn't like the way it flashed and caused
the crazing to be emphasized from the sudden heat. I then wrapped paraffin
in foil to slow down the burning. That worked quite well and I got some
beautiful reds, no soot or scraping. 

 

Then when I taught in Denmark, on visiting the numerous potters there, I
found that they used an electric kiln in which reduction could be done. They
had even achieved high fire reduction with iron spots and nice finished
glazes. The elements were very heavy and wound to a ID of 1". It was made of
soft firebrick in a metal case with a small sized hole in the roof which I
closed during the firing. In checking the manufacturer of the kiln, found it
was made in England. However, during the introduction of a candle in the
tunnels drilled in the insulating firebrick of the floor with small fume
drills into the interior, I observed or smelled no smoke.  When teaching at
the Vra school, I introduced many of the things we did in the US, such a
smoke firing, press molds, etc. So when I saw this kiln in the school, I
decided to go for a copper reduction firing. I had the students all decorate
their pots with the base glaze and then a wash of copper carbonate and a
touch of iron oxide, the students all submitted their pots on my hopes of
achieving a good firing. The pots were fired to Cone 04, then on cooling at
1200 deg. F, introduced the candle. Everything went on schedule and looking
through the peeps to see if we had obtained any red, couldn't see any. But
when opening the kiln the next day, every pot had the beautiful red
decorations, softened in color with the iron oxide. The head of the
department was quite impressed with my methods and notified teachers in
other Danish schools to come observe. This was so nice and they invited me
back for another term the following year. 

 

I looked into perhaps purchasing one of these kilns from the English
company, but the cost was prohibitive in my financial position at the time,
so we pursued other avenues of achieving copper reds in the pit fires when I
worked with Ed Gray. He now lives in the copper country in the Upper
Peninsula where the earth is inundated with copper and he gets reds easily. 

 

Thanks for listening.

 

Bonnie

 

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