Liz Willoughby on fri 20 apr 01
Dear Hank,
Thanks for those tips on firing to get better reds. Just to clarify
what I am doing with refiring those shino pots of mine, I am doing it
in my electric kiln, with a controller. And I am in love with the
results.
Now a question. Do you aim for carbon trapping along with increased
depth of red/orange color? If I get carbon trapping and perhaps some
of those marvellous haloed crystals that are a joy, from going into
reduction at cone 012, will I lose those crystals or the carbon if I
relight and soak at 1900-2000 F on the way down, or are they in there
to stay? These pots that I am refiring looked a like they had dirty
carbon on them, and some of it did go away, the glaze became more
fluid, more gold and lustred, but where the carbon had trapped
heavily it left a beautiful textured pebbly surface which was smooth
to touch and very tactile. I imagine the carbon is trying to get
out, and I am wondering if I re-fired a little higher, maybe between
1960 to 2000 F or perhaps soaked for two hours the surface would
smooth out completely without the texture. Probably the only way to
find out is to try it. What do you think? I use tenmoku too, will
that glaze be affected by the soak, i.e. more crystals?
Best regards,
Meticulously loose Liz
>Hank replies;
>
>Dear Liz, try firing your normal way to shutoff, then cool slowly down to
>around 1900F-2000F and start up the kiln again about 1/2 power or enough to
>hold the kiln IN OXIDATION at that temperature for 2-8 hours.
>
>I get real spectacular shino reds from this sort of cooling treatment. Now
>I have re-considered the cooling cycle as an ACTIVE part of the firing.
>Works well for my C/10 Oxidation glazes too. Once you learn to set up your
>kiln to hold temperature in oxidation, you won;t lose any sleep.
>
>This technique doesn't improve color in shiny, well-melted glazes, but will
>work wonders for any microcrystalline glazes like shinos and copper blues,
>greens, and yellows, and also glazes like reitz green.
>
>Good luck, and thanks for paying close attention to Malcolm's demo!
>
>Hank in Eugene
Liz Willoughby
RR 1
2903 Shelter Valley Rd.
Grafton, On.
Canada
K0K 2G0
e-mail lizwill@phc.igs.net
Chris Clarke on fri 20 apr 01
here's the link to the new pieces i got out of the kiln with the wax =
marks
http://www.ccpots.com/html/thebasics.htm
next i'll try the hot soda ash, chris
=20
chris@ccpots.com
www.ccpots.com
Liz Willoughby on fri 20 apr 01
Dear Chris,
I just had a look at the photo's that you posted of the Copper Red
Glazed pot with wax resist lines and the shino pot with wax resist
lines. Thank you so much for posting those pictures. This is what
is so great about clayart, the word and the visual.
I think it was me that put the post up about wax resist on shino
pots. I learned it from Malcolm Davis. He was here a few years ago,
and we did a firing and he showed me the technique. If you have seen
his very delicate wax resist drawings on his plates and vessels you
will know what I mean. He had some beautiful work in Charlotte and
in Asheville.
Mel talked about how difficult it is to work with shino, and he is so
right. For me it is best not to have a whole kiln load of it or I
would end up stark raving mad. When it works; for me, it is the best.
Lately I have been trying re-firing some shino pots (dead/or with too
much carbon) in oxidation. I had tried before to bisque (04/05), and
wasn't happy with the results. There was a very fine network of
crazing marks, you could almost feel them when you touch them. Then
Hank Morrow put up a post saying to fire to 1920 F, and soak for an
hour. (I think that is what he said, my apology if that is not
right). Tried that, not happy. Then I went to 1940 F, soaking an
hour, and 1950 for 1 1/2 hours. The color did improve, on the inside
quite orange, on the outside, GOLD, glaze was shinier, less crazing,
and the carbon trapping on some had a smooth pebbly surface. My clay
is porcelain, glaze fired in propane to c/10,11.
Why am I doing this. Well, I was getting a pretty big stack of pots
with good form, but without good firing results. And thought, why not
experiment with these pots?
I would encourage you to read Mel's article in Ceramics Monthly, and
Pete Pinnell's 4 part series on shinos last year in Clay Times. And I
am looking forward to reading Hank's article.
My experience with shino is that just when you feel secure with what
you are doing, wham!!!bang, out the window she goes. What keeps me
using it, is that when it works it can be outstanding.
This is a post that Hank Morrow wrote to Ivor Lewis on clayart last
year that you might find interesting.
Best regards,
Liz
At 8:16 AM -0800 12/5/00, Hank Murrow wrote:
>
> >Ivor Lewis wrote in part;
>
> >Looking over a recent porcelain test tile bearing recipes based on a high
> >soda felspar I noticed a >pale orange halo around some of the melts. The
> >anomalous nature of this colour became caught my >attention because the
> >glaze samples associated with the colour were well reduced and exhibited
> >what >seemed to be a typical blue green celadon hue. I started to wonder
> >how it could be possible for >iron to behave as though it has been both
> >oxidised and reduced in areas that are immediately >adjacent. So, how are
> >the orange colours, which develop where a Shino glaze is thin, explained?
> >>There seems to be a contradiction. So, who can explain orange in
> >reduction?
>
>Dear Ivor;
>
>The orange color is from iron which has been reduced, congregated in a
>micro-crystaline network at the surface of the glaze, and oxidized for some
>time after the reduction. Sometimes i fire in reduction to C/2 and for ten
>hours after that in oxidation to C/10, folowed by a slow cool. Other times
>I fire in reduction to C/10, cool to C/3, then relight the kiln, hovering
>there in oxidation for several hours,then cooling normally. If you break a
>piece of orange shino open and examine the shard, you will discover that
>the orange layer is so thin you can't measure its thickness without the aid
>of a microscope with a reticulated eyepiece, as the orange layer is only
>20-40 microns thick, and the glaze is white underneath the orange! Where
>your glaze is showing a celadon color, the iron did not crystallize out,
>remaining in solution in its reduced form to yield a celadon. If you want
>the whole piece to go orange, try cooling much slower to encourage the
>micro-crystalline growth. It also helps to get tiny amounts of chlorine or
>fluorine into the recipe to loosen the iron from the clay and carry it to
>the surface where it stays behind to re-oxidize, while the Cl or F
>outgasses.
>
>I hope you have success with these suggestions, Hank in Eugene
>here's the link to the new pieces i got out of the kiln with the wax marks
>
>http://www.ccpots.com/html/thebasics.htm
>
>next i'll try the hot soda ash, chris
>
Liz Willoughby
RR 1
2903 Shelter Valley Rd.
Grafton, On.
Canada
K0K 2G0
e-mail lizwill@phc.igs.net
Marcia Selsor on fri 20 apr 01
Dear Chris,
Thanks for posting the photos. That is a very interesting phenomena.
-never heard of it before.
good forms too!
Marcia in Montana
Chris Clarke wrote:
>
> here's the link to the new pieces i got out of the kiln with the wax marks
>
> http://www.ccpots.com/html/thebasics.htm
>
> next i'll try the hot soda ash, chris
>
>
>
> chris@ccpots.com
> www.ccpots.com
>
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Marcia Selsor
selsor@imt.net
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Hank Murrow on fri 20 apr 01
Liz wrote in part;
>I think it was me that put the post up about wax resist on shino
>pots. I learned it from Malcolm Davis.
>Then Hank Morrow put up a post saying to fire to 1920 F, and soak for an
>hour. (I think that is what he said, my apology if that is not
>right). Tried that, not happy. Then I went to 1940 F, soaking an
>hour, and 1950 for 1 1/2 hours. The color did improve, on the inside
>quite orange, on the outside, GOLD, glaze was shinier, less crazing,
>and the carbon trapping on some had a smooth pebbly surface. My clay
>is porcelain, glaze fired in propane to c/10,11.
Hank replies;
Dear Liz, try firing your normal way to shutoff, then cool slowly down to
around 1900F-2000F and start up the kiln again about 1/2 power or enough to
hold the kiln IN OXIDATION at that temperature for 2-8 hours.
I get real spectacular shino reds from this sort of cooling treatment. Now
I have re-considered the cooling cycle as an ACTIVE part of the firing.
Works well for my C/10 Oxidation glazes too. Once you learn to set up your
kiln to hold temperature in oxidation, you won;t lose any sleep.
This technique doesn't improve color in shiny, well-melted glazes, but will
work wonders for any microcrystalline glazes like shinos and copper blues,
greens, and yellows, and also glazes like reitz green.
Good luck, and thanks for paying close attention to Malcolm's demo!
Hank in Eugene
Hank Murrow on sat 21 apr 01
Liz wrote;
>Dear Hank,
>Thanks for those tips on firing to get better reds. Just to clarify
>what I am doing with refiring those shino pots of mine, I am doing it
>in my electric kiln, with a controller. And I am in love with the
>results.
>
>Now a question. Do you aim for carbon trapping along with increased
>depth of red/orange color? If I get carbon trapping and perhaps some
>of those marvellous haloed crystals that are a joy, from going into
>reduction at cone 012, will I lose those crystals or the carbon if I
>relight and soak at 1900-2000 F on the way down, or are they in there
>to stay? These pots that I am refiring looked a like they had dirty
>carbon on them, and some of it did go away, the glaze became more
>fluid, more gold and lustred, but where the carbon had trapped
>heavily it left a beautiful textured pebbly surface which was smooth
>to touch and very tactile. I imagine the carbon is trying to get
>out, and I am wondering if I re-fired a little higher, maybe between
>1960 to 2000 F or perhaps soaked for two hours the surface would
>smooth out completely without the texture. Probably the only way to
>find out is to try it. What do you think? I use tenmoku too, will
>that glaze be affected by the soak, i.e. more crystals?
Dear Liz;
My answer is to point out that there are at least two prevalent schools of
ShinoThought in the nation, The Soda Ash School & the Other School. Because
I am of the Other School, I don't know what your carbon trapping will do
when soaked in OX during cooling. My shinos resemble more the Japanese
"curdly white with firecolor" shinos, and they get bloody red with such a
cooling cycle. Thus, I get a range of firecolor from one or two recipes
depending entirely upon the cooling cycle they receive.
I think the gold color is due to the soda ash and oxidation.
As to the Tenmoku, If black tenmoku is what you are after, they like to be
cooled quickly to keep the iron in suspension in the glaze.
On the other hand, if your tenmokus are the rusty kind, you may find that
this is intensified by an oxidized soak during cooling.
All of this suggests to me that we potters may need to have a smaller kiln
in the studio to try these suggestions without committing a huge load to an
uncertain result.
Good Luck, Hank in Eugene
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