Dale Mark on wed 8 mar 00
Thanks for the compliment Tom.
The firing schedule is simple for all my glazes. I tend to switch the
start of reduction around depending on the amount of copper red vessels in
the kiln; either cone 010, cone 08 or cone 06 (sometimes 04). It doesn't
seem to matter for my glazes (although I suspect for copper earlier the
better). Reduction is fairly strong until cone 10/11, at which time the
kiln is shut off. I think the kiln cools slowly and this helps the copper
red form; or put this way my kiln cools at a rate beneficial to the
formation of reds.
Reading about what other people do and testing many red glazes, I find
glaze recipe, kiln, and firing schedule are intimatley bound together-
what works for me probably won't work for others. I fire the copper glazes
along with others that love strong reduction, so I devised copper glazes
that work under these conditions. In general, I find there is a difference
in the quality of the glaze and colour under varying reduction
atmospheres- the stronger throughout the better for me. I don't have the
instruments to measure but I feel that there are various points in the
firing when reduction is essential, one of them being somewhere
between cone 012?/010 and cone 06/04?, another somewhere higher(and
others?). There are probably points where it doesn't matter if the
reduction firing is in oxidation. I have had carbon trapping in oxidized
glazes which doesn't seem possible(or does it?).
On the topic of black glazes on porcelain I agree with Ron, opaque glazes
zing on a porcelain body. I find differences even amongst porcelain
bodies. If the black is an iron saturate, the effect of edge breaks and
the whiteness of unglazed foot add to the quality of the overall
appearance, something lacking with a non-porcelain body. Is the glaze
truly opaque, or is some light going through hitting the white body and
coming out or being trapped within? Differing results if differing body
colours? Some glazes look better on some bodies: iron saturates on
stoneware or porcelain, copper red on stoneware or porcelain, shino on
stoneware or porcelain, ash glazes on stoneware or porcelain.
The question is not why someone puts black on white, but why white on
black.
Salut,
Dale Mark
Hamilton, ON
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