Paul on sun 2 mar 03
Has anyone seen considerable changes in the color of copper reds based on
the cooling cylce? Mine usually come out purple-red or even with blue tints
in a kiln that cools very slowly. Most parts of the kiln reach cone 11 so i
am trying to find out if it is the higher temperature or slow cooling that
causes this. The same two recipes i used in a smaller kiln with about the
same amount of reduction generally had a more ruby-red color which i would
like to start getting again at least once in a while, although that kiln was
usually not fired as hot. So would it be the temperature or the cooling rate
(or both), that cause this effect?
Paul B
Daniel Dermer on tue 4 mar 03
In my last firing, I experimented with using saggars
around two copper red pots, right next to a third, UN-
saggared copper red pot. I heard that using a saggar
improved the color and surface quality of copper reds -
- presumably because of slower cooling and keeping the
pots away from direct flame -- and I wanted to test
that.
The results were... interesting. One of the saggared
pots turned almost dark wine (burgundy) color -- much
darker than my usual coppper red results, usually
stawberry/cranberry reds. The surface was also much
rougher. I think the glaze cooled too slowly and
became de-vitrified.
The other saggar-fired piece which had a different
copper red glaze only turned red on a very small patch
at the bottom of the pot. It was in the one position
on my bottom kiln shelf where I thought I was having
trouble with flames oxidizing the copper right out of
the glaze. I had figured that a saggar would shield
the pot and give me the copper red color I was looking
for... NOT. I'll have to keep experimenting there...
So far, I like my un-saggared pieces best. I'll try
to post some pictures so you can see the differences
in results between saggared and un-saggared copper
reds, but won't be able to until this weekend.
-Dan
Dannon Rhudy on wed 5 mar 03
Dan said:
> In my last firing, I experimented ...I heard that using a saggar
> improved the color and surface quality of copper reds ->
One of the saggared
> pots turned almost dark wine (burgundy) color --
The surface was also much
> rougher. I think the glaze cooled too slowly......
The most likely reason for your saggared pot having a
rough surface is that it did not get hot enough inside
the saggar. Remember that it takes longer for the pot
to heat up, because the saggar not ONLY slows the
cooling, it also slows the HEATING. I have noted in
the past that underfired copper reds will often have a
much darker color than those fired to a thorough melt.
regards
Dannon Rhudy
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