Craig Martell on mon 13 aug 07
Hello Red glaze enthusiasts:
There's been some discussion in the recent past about Iron reds and how
certain types of firing will make the reds work. The main idea has been
that a crystalline state needs to happen to make iron reds. I agree that
this is the deal so I had some lackluster stuff going on and thought
perhaps I could make some improvements.
Some years back I made a frit substitution for another clayart potter in a
glaze called Berry Rust which is mainly an oxidation iron red. I fired it
to cone 10 ox and cone 10 R and damned if it didn't work ok in both
firings. I put it on the back burner for many years but started doing some
tests recently.
I wanted to get a nice iron red over wax resist decoration on celadon
glazes so I made a bunch of tiles and used Berry Rust over four different
celadons. The tiles were ok but the Berry glaze was more of a green and
brownish green than red when used by itself. Not surprising. So I refired
the tiles to cone 03 (1988F) in the electric. The glaze was very iron red
and the celadons were richer and deeper with more crystal development. So
what I'll probably do is not refire them in the electric but downfire in
the gas kiln when it cools to about 1950F and hold the kiln in oxidation at
that temp for however long it takes to make the crystalline iron reds over
the celadons. The limestone in the celadons is very good at taking iron
into solution, thus the green and greenish brown with the Berry Rust. But
if you hold temp at the crystal forming phase and devitrify the glaze
somewhat the red will develop. That's what I think anyway.
Also, I've been working on some copper reds and got one that I liked that
wasn't as red as I wanted it to be. Refired in the electric kiln at 1988F
it went from a tranlucent red or reddish purple to and very rich opaque
copper red. So I think a hold in oxidation in the gas kiln will do the
trick with that glaze too.
Hope this is of some interest and if I'm missing something, lemme know.
regards, Craig Martell Hopewell, Oregon
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