Lana Reeves on thu 7 dec 00
Hi, I've been reading the shino posts, very interesting. But-- where =
does the orange come in when there is no iron present? Eg., Chris =
Gustin Shino contains no iron, yet goes orange on porcelain. Why? =
Thanks,
Lana in Somerville, MA
kilnkat@rcn.com=20
Hank Murrow on thu 7 dec 00
>Hi, I've been reading the shino posts, very interesting. But-- where does
>the orange come in when there is no iron present? Eg., Chris Gustin Shino
>contains no iron, yet goes orange on porcelain. Why? Thanks,
>Lana in Somerville, MA
Dear Lana;
There is usually some iron in the Lithium materials, like spodumene or
petalite. Check your recipe and then look up the materials' empirical
formula for a peek at the iron content. Incidentally, if you break open a
sherd of shino, you will find that under the orange surface the glaze is
white. My measurements show that the red color is a fine ferric
micro-crystalline network which is around 20 microns thick. That is 20
MILLIONTHS of a meter! And in rough service(like a restaurant), it abrades
easily, revealing the white underneath.
Regards, Hank
Craig Martell on thu 7 dec 00
Lana wanted to know:
>But-- where does the orange come in when there is no iron present? Eg.,
>Chris Gustin Shino contains no iron, yet goes orange on porcelain. Why?
The Orange comes from iron. While there may be no "added" iron, there has
to be iron in some of the glaze raw materials. If you look at analyses of
spars, clays, etc. there is most always some trace iron or perhaps a bit
more. Shinos will bring out small amounts of Fe whereas these tiny amounts
of iron are lost in other glazes.
regards, Craig Martell in Oregon.
iandol on sat 9 dec 00
Dear Lana,
This is one of the question which came into my mind when I first started =
this thread. Then I realised that not only did my wollastonite have iron =
as a contaminant, so do many clays. It is almost impossible to get rid =
of some of the marginal or residual elements which contaminate most =
natural compounds.
I could not understand why it was possible to get both a green/blue and =
an orange colour in a reduction firing. Now I know!!!
Best regards,
Ivor
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