LINDA BLOSSOM on sun 19 jan 97
I knew I had read this somewhere. It comes from the Energy Efficient
Potter and I liked it especially because it wasn't theory or speculation.
Instead it was direct experience. So here goes. From page 128: " George
Wettlaufer has experimented with the effect of the cooling rate on copper
red glazes. He took draw tiles from his kiln as the firing progressed to
cone 10 and also as the kiln cooled. He took them out at 1000 , 1100 ,
1200 , then after the kiln ws shut down at 1200 , 1100, 1000, and 900.
While cooling, these draw trials were pale green in color at 800 and had a
slight coloration at the edges. At 700 the draw trial had almost half of
its potential red color. The draw trial taken out at 600 had the copper
red fully developed. Draw trials left in the kiln had the same copper red
color as the sample taken at 600 . " Regis Brodie then goes on to say: "
For matt glazes you may cool quickly to 900 C then a slow cooling is
suggested between 900 and 800. Shiny glazes and copper red glazes can be
cooled quickly to 700 and then slowly cooled. " He mentions the dunting
pints and is less concerned with the one between 600 and 550 but feels the
one from 260 to 220 is more important. This certainly in agreement with
what Mel says. My kiln is very insulated and I usually got good results
when I left the damper open a couple of centimeters after shutting down
and then opened the damper wider in the morning when the temp was around
200. (All temps are in centigrade) Lately I have been seeing more of a
blood red. In my last firing a bowl with a red glaze that has been doing
just this didn't bother to turn red at all. However, near it was another
with the same glaze over a red iron glaze. It went red. Blood red,
however. Another red was so rich, creamy, opaque, lighter red that I'll
post the recipe soon. It's just too cold to go back out to get it.
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