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glaze help: oxidation on outside of pot, reduction on the inside?

updated sat 7 may 05


dannon rhudy on thu 5 may 05

of the cassarole is a beautiful red. The outside is a super light greenish

There are always lots of possibilities, with copper reds.
However, this case sounds like a classic case of too-
fast cooling. The usual reason that a piece is red inside
and not red outside is that the inside cools more slowly.
Copper reds achieve their color in the cooling phase of
the firing. Most beginners with copper reds puzzle a lot
about why their pieces are a beautiful red inside, and
not-red outside. Read the articles in Clay Times, by Pete
Pinnell. He did a series on copper reds a year or two
ago, four articles I believe. You will find them extremely
helpful. Copper red glazes are also sensitive to thickness
of application: too thin - no red. They need to be thick,
so choose a stable recipe (Pinnell has three-four in the
articles, and all are stable to Cone 10 in my experience).

Get the reduction right - I begin mine at about 012, and
continue in light (repeat: LIGHT) reduction through the
rest of the firing. If the kiln cools too fast, re-light it at
about 1900 F, and let it cool slowly to perhaps 1200F.
Your reds should be/stay red. I did a summer-full of
copper red firings in Olympic's little raku kiln. Every
piece was consistently red, inside and out. If it can
be done in THAT kiln, it can be done in any.


Dannon Rhudy

BJ Clark | Stinking Desert Ceramics on thu 5 may 05

Hello all,
I am asking this for a friend.
I fired a copper red glaze (C10R - Copper Carb being the colorant -
Walter Donald Kring Red found via google) on a cassarole. The inside
of the cassarole is a beautiful red. The outside is a super light
greenish white.

My explaination is that the kiln reduced at the beinging and was
oxidized toward the end of hte firing. When it reduced at the begining
the inside of the cassarole reduced as well as the outside, however
when the kiln was then oxidized, the out side of the pot oxidized
while the inside was still in a reduction atmosphere.

My friend's suggestion was that the inside of a vessel never reduces
because "the flames never get in there and no carbon can get there".=20
He says that the glaze must like a very very light reduction and that
the kiln was over reduced (even though I told him the kiln was
misfired and was oxidized) and that all the copper had been pulled out
of the form.

FYI, the exposed clay on the bottom was very light for the body (iron
bearing) and other glazes came out looking like they were

With the little information provided, anyone dare to venture a guess
as to what happened?

BJ Clark
Stinking Desert Ceramics