Peter Atwood on thu 29 jul 99
Hi All,
I noticed an interesting phenomena recently. I have checked all the posts in
the archives and saw a couple of things that may be pertinent but no real
explanation for it. This is what happened:
My friend Marcia (who reads this list) recently fired a shino bowl. She got
carbon trapping in three specific places- on the rim where her fingers had
been as she held the bowl to dip it in the slurry. While the glaze was still
wet she touched up the finger marks with a little glaze on her fingertip.
All three points showed up with carbon trapping. Why?
One post from the archives mentions that if you apply wax over shino it is
possible to get carbon trapping at the edge of the wax apparently where the
soda ash has migrated presumably as the water escapes the drying glaze. This
idea got me thinking about oil from her fingers but since it was not on top
of the glaze I don't think that explains it.
Dannon mentions applying soda ash on top of the glaze to create a streaking
carbon trap effect. Could it be that Marcia dipped her finger in the glaze
and was in effect applying a little extra soda ash to the top of the glaze?
In that case wouldn't just applying another coat of shino tend to produce
carbon trapping on the whole piece?
Any thoughts on this matter would be most appreciated.
--Peter Atwood
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Liz Willoughby on sun 1 aug 99
Hello Peter,
Those that fire regularly using carbon trap shinos can still be seen to
shake their heads in wonder half the time. It seems to be one of those
glazes that have many variables. More like "what carbon control".
First, you need an early reduction, C/012 or 010, heavy for one hour, and I
continue with a fairly good reduction to C 10.
>My friend Marcia (who reads this list) recently fired a shino bowl. She got
>carbon trapping in three specific places- on the rim where her fingers had
>been as she held the bowl to dip it in the slurry. While the glaze was still
>wet she touched up the finger marks with a little glaze on her fingertip.
>All three points showed up with carbon trapping. Why?
I believe that it is the extra glaze that she applied that gave it the
carbon trap. If my glaze is double dipped and is in a certain place in the
kiln, it goes VERY black. If I dip once, and then paint a thin line of wax
on top, and then dip again, I get an orange line, and black around it. If
I don't double dip, it is better, dark, but not black.
>One post from the archives mentions that if you apply wax over shino it is
>possible to get carbon trapping at the edge of the wax apparently where the
>soda ash has migrated presumably as the water escapes the drying glaze. This
>idea got me thinking about oil from her fingers but since it was not on top
>of the glaze I don't think that explains it.
I don't think the oil on her fingers has any bearing. I do have a mug that
I picked up before it was completely dry, and it left "white" circles where
the glaze was compressed, I think my fingers were acting as a resist so the
salts couldn't come to the surface.
>Dannon mentions applying soda ash on top of the glaze to create a streaking
>carbon trap effect. Could it be that Marcia dipped her finger in the glaze
>and was in effect applying a little extra soda ash to the top of the glaze?
>In that case wouldn't just applying another coat of shino tend to produce
>carbon trapping on the whole piece?
I prefer to only dip once. And if I am lucky, I do get wonderful carbon
trapping, I call them crystals, but they are more like oil spots with halos
around them. You can spray extra soda ash, or even roll the glazed pot
over a sprinkle of salt. Or paint dots of concentrated soda ash on the pot.
The interesting thing is that you can have a shelf of pots glazed in shino
and each one of them might be different. White, orange, speckled
white/orange, black, black green, or that one you hunger for, with
beautiful black dots with halos.
I must be nuts to use this glaze. Was at a show last week, I said to one
potter that shino was like an "addiction", and his reply was, more like
an"affliction".
Too right. Best, Liz
>
Liz Willoughby
R.R.# 1
2903 Shelter Valley Rd.
Grafton, Ontario
K0K 2G0
Canada
e-mail, lizwill@phc.igs.net
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