Teri Hannigan on mon 7 jan 08
I've been trying to find consistent information on Carbon trapping with shinos so that I can
understand why we're having such a problem achieving good CT results at our community college
studio.
Our attempts at carbon trapping often result in a weird green. Where wax has been applied to the
surface, it's a firey orange with a shimmery gold halo. Great, but otherwise no blackish grey
indicating carbon trapping--only what has been described in this forum as "snot green," which
perfectly describes what we're getting. Hey, I have nothing against puke (or snot) green, but
that's not the carbon trapping I long for. I've searched and researched the internet, including this
forum and in books and magazines, but can't find the information I seek. Hoping to find
answers, I'm desperately seeking articles on carbon trapping from an old issue of Studio Potter.
Without success--this back issue is out-of-print (below).
Here's what's consistent in our community college studio:
-Claybody=B-mix/w/sand
-Shinos used for CT contain about 17% soda ash and some iron content; applied to bisqued ware
-Reduction starts at cone 08 and continues throughout for the copper reds to cone 10
Here's why I'm so confused and remain such an ignoramus on the subject:
1. Some say let shino-glazed ware sit (up to 2 weeks!) before firing so sodium crystals develop on
the surface; others say fire immediately for best CT results.
2. Most experts say to start reduction early in the firing cycle, but their answers range from cone
010-cone 014. I understand that soda ash melts at a relatively low temperature, 1550 degees F,
so it makes sense to start reduction before that. But when, exactly?
3. Some say reduction, as measured by an oxyprobe reading of 70-80, say, doesn't necessarily
mean soot (carbon) is being developed on ware inside the kiln. They say that the best indication
of carbon development is smoke (soot) emanating from the peep holes and door cracks. Whew!
Not a good time to be in the kiln room, and I hope the kids from OSHA don't mind! I've been
further cautioned that there shouldn't be any increase in kiln temperature while soot is being
developed. Otherwise, the carbon will "burn off" before the soda ash melts. Unfortunately, our
kilns have no pyrometers, nor do we own an oxyprobe. Firings are done with several cone packs
(9,10, 11 and 08, 09, 010) We're installing 2 new Geil kilns (+ pyrometers) this summer, so
hopefully we'll be able to control firings more scientifically. Is an oxyprobe helpful for carbon
trapping?
3. Some say reduce all the way through the firing--if you oxidize after development of carbon
that the carbon will burn out and defeat any efforts at carbon trapping. Others say reduce hard
and early for an hour or so then gradually switch to neutral or oxidation at the end.
4. Some say that the weird green is due to enough reduction for iron to turn green in the glaze,
but not enough soot (carbon) deposited on the surface before the soda ash melts. I've wondered
if that "ashy" green color we've gotten is from the carbon, in the form of ash, merging with the
melting soda ash due to not reducing (creating carbon) before the soda ash has a chance to melt
and "trap" the carbon.
5. Some say you can't fire copper reds in the same kiln as CT shino, but I haven't been able to
discern what the problems are and why--especially if the soda ash has already melted and
vitrified, trapping the carbon beneath.
Tony, Sheila, Steve, Judith, Matt, Liz, Shirley, Harvey and last
but certainly not least, Malcolm--and anyone else I've left out--Help!
I'mobsessed!
No Longer Available:
Studio Potter issue 30 #2 (June 2002)
CARBON-TRAPPING ALONG THE OLD SHINO TRAIL
CONFESSIONS OF A CARBON-TRAPPER by Malcolm Davis
MY SECRET LIFE AS A SHINO ADDICT AND CARBONTRAPPER by Harvey Sadow
TWO BOWLS by Shirley Johnson
MOVING FORWARD by Liz Willoughby
CARBON- TRAP: HOW AND WHY by Matt Long
CARBON-TRAP SHINO by Judith Duff
CARBON-TRAPPING SHINO GLAZE by Steve Loucks
THE GHOST OF CARBON PAST by Tony and Sheila Clennell
Hank Murrow on mon 7 jan 08
On Jan 7, 2008, at 9:18 AM, Teri Hannigan wrote:
> I've been trying to find consistent information on Carbon trapping
> with shinos so that I can
> understand why we're having such a problem achieving good CT
> results at our community college
> studio.
In my opinion you are not reducing early enough. I reduce beginning
at 84 on my OxyProbe, which is around cone 013. My reduction is not
heavy, but my kiln is almost hermetically sealed except for burner
ports and flue. For more on my approach, including the regime for a
soak in oxidation during the cooling, see:
http://www.ceramicsmonthly.org/mustreads/shinofire.asp
I should mention that I use no soda ash in my shinos, and the reddish
colors from pink to bloody are my preference. Check it out.
Cheers, Hank
www.murrow.biz/hank
Liz Willoughby on mon 7 jan 08
Hello Teri,
I understand completely what you are going through. I am sure that I
am not the only one that had an article in that Studio Potter that
still finds that being successful at achieving good carbon trapping
could be just the way just the way the stars are lined up on a
particular night. Saying that, I do think there are some things that
you do, that should help achieving your goal.
1. If your glaze has too much soda ash, it will turn snotty green.
This can also happen if your glaze is too thick, or your bisque too
low (hence, it will absorb more glaze). However, if the glaze is too
thin, it does not c.t. and could be just orange, or just white!
2. Clay body. . .well you know that Malcolm uses porcelain, so do I,
though a different one. With stoneware you will get a deeper
orange/red, and a much softer carbon trapping. With the porcelain
the contrast is better.
3. Wax does work. Try glazing, then waxing, then a quick dip again
in glaze for a c.t. edge.
4. I go into reduction at cone 010-012, but have seen good carbon
trapping on pots from going into reduction at cone 08. I do not have
anything but a pyrometer, and cone packs. I do like to see smoke
coming out around the top of the door after going into reduction.
That is also where I get good carbon trapping.
5. I am one that likes to stack my shinos soon after glazing, that
is the day of or the day before stacking and putting on my pilots.
They stay on for a few hours, then I put my burners on low overnight.
I keep it in heavy to mod. reduction throughout the firing to cone
10. (middle of kiln goes to 11) I have a Bailey, propane gas.
6. Ron (Roy) has a Geil, and fires very nice shinos in it. His shino
is not a carbon trap shino, but he has fired a few pieces of mine in
that kiln and have come out with nice C.T. So you just might be in
luck with the new kiln, and he does not go into reduction as early as
I do.
Teri,
I have another copy of the Studio Potter that you want/need. It is a
good issue, with lots of good info in it. Where are you located? I
will gladly send it to you.
Just need your address.
You can e-mail privately if you want,
lizwill@phc.igs.net
Liz from Grafton, Ontario, Canada (who lusted after a carbon trap
shino, after seeing a tea bowl of Malcoms in 1986 or 87, later in the
90's came a lot of tests fired in Ron's old kiln in Toronto, where I
just knew that that was the glaze for me, moved to the country, got a
gas kiln, and then the frustration/satisfaction/ began and I became
completely nuts over the glaze. Not easy though, had an awful lot of
disappointments. Still learning, just when you think you have nailed
it. . . it is gone!)
>
>Our attempts at carbon trapping often result in a weird green.
>Where wax has been applied to the
>surface, it's a firey orange with a shimmery gold halo. Great, but
>otherwise no blackish grey
>indicating carbon trapping--only what has been described in this
>forum as "snot green," which
>perfectly describes what we're getting.
>
>Here's what's consistent in our community college studio:
>-Claybody=B-mix/w/sand
>-Shinos used for CT contain about 17% soda ash and some iron
>content; applied to bisqued ware
>-Reduction starts at cone 08 and continues throughout for the copper
>reds to cone 10
>
>Here's why I'm so confused and remain such an ignoramus on the subject:
>1. Some say let shino-glazed ware sit (up to 2 weeks!) before
>firing so sodium crystals develop on
>the surface; others say fire immediately for best CT results.
>2. Most experts say to start reduction early in the firing cycle,
>but their answers range from cone
>010-cone 014. I understand that soda ash melts at a relatively low
>temperature, 1550 degees F,
>so it makes sense to start reduction before that. But when, exactly?
>3. Some say reduction, as measured by an oxyprobe reading of 70-80,
>say, doesn't necessarily
>mean soot (carbon) is being developed on ware inside the kiln. They
>say that the best indication
>of carbon development is smoke (soot) emanating from the peep holes
>and door cracks. Whew!
>Not a good time to be in the kiln room, and I hope the kids from
>OSHA don't mind! I've been
>further cautioned that there shouldn't be any increase in kiln
>temperature while soot is being
>developed. Otherwise, the carbon will "burn off" before the soda
>ash melts. Unfortunately, our
>kilns have no pyrometers, nor do we own an oxyprobe. Firings are
>done with several cone packs
>(9,10, 11 and 08, 09, 010) We're installing 2 new Geil kilns (+
>pyrometers) this summer, so
>hopefully we'll be able to control firings more scientifically. Is
>an oxyprobe helpful for carbon
>trapping?
>3. Some say reduce all the way through the firing--if you oxidize
>after development of carbon
>that the carbon will burn out and defeat any efforts at carbon
>trapping. Others say reduce hard
>and early for an hour or so then gradually switch to neutral or
>oxidation at the end.
>4. Some say that the weird green is due to enough reduction for
>iron to turn green in the glaze,
>but not enough soot (carbon) deposited on the surface before the
>soda ash melts. I've wondered
>if that "ashy" green color we've gotten is from the carbon, in the
>form of ash, merging with the
>melting soda ash due to not reducing (creating carbon) before the
>soda ash has a chance to melt
>and "trap" the carbon.
>5. Some say you can't fire copper reds in the same kiln as CT
>shino, but I haven't been able to
>discern what the problems are and why--especially if the soda ash
>has already melted and
>vitrified, trapping the carbon beneath.
>
>Tony, Sheila, Steve, Judith, Matt, Liz, Shirley, Harvey and last
>but certainly not least, Malcolm--and anyone else I've left out--Help!
>I'mobsessed!
>
>No Longer Available:
>Studio Potter issue 30 #2 (June 2002)
>CARBON-TRAPPING ALONG THE OLD SHINO TRAIL
>CONFESSIONS OF A CARBON-TRAPPER by Malcolm Davis
>MY SECRET LIFE AS A SHINO ADDICT AND CARBONTRAPPER by Harvey Sadow
>TWO BOWLS by Shirley Johnson
>MOVING FORWARD by Liz Willoughby
>CARBON- TRAP: HOW AND WHY by Matt Long
>CARBON-TRAP SHINO by Judith Duff
>CARBON-TRAPPING SHINO GLAZE by Steve Loucks
>THE GHOST OF CARBON PAST by Tony and Sheila Clennell
June Perry on mon 7 jan 08
A trick with carbon trapping is that after a heavy early reduction period,
speed up the kiln for a bit. This was something Warren Mckenzie recommended
some years ago.
The amount carbon trapping will depend on your timing and amount of
reduction and the speed and amount of temperature rise as well as your shino recipe.
Regards,
June
_http://www.shambhalapottery.com_ (http://www.shambhalapottery.com/)
_http://shambhalapottery.blogspot.com_
(http://shambhalapottery.blogspot.com/)
_http://groups.yahoo.com/group/sodasaltfiring_
(http://groups.yahoo.com/group/sodasaltfiring)
**************Start the year off right. Easy ways to stay in shape.
http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489
Neon-Cat on mon 7 jan 08
This carbon trap shino recently worked well for me at Cone 6 reduction on a
local white stoneware to produce pleasing carbon trapping in a pretty light
orange color blending to a tannish color. However under the same kiln
conditions on a local red stoneware this glaze produced only a nice,
uniform, vivid orange-red color. Offhand I don't recall our UTA firing
schedule except that the large kiln contained a mixed bag as far as an
assortment of ware and glazes (including copper reds) is concerned with a
body reduction period followed by a glaze reduction period. (Our reduction
firings never produce visible soot or smoke from peep holes or other areas -
we could have a party in the outdoor kiln area.)
Orange Carbon Trap Shino -- cone 7
c/o James Q. Jacobs, Mesa Community College, Hawaii
http://www.jqjacobs.net/art/glazes2.html
nepheline syenite 160
soda ash 48
OM-4 ball clay 60
custer feldspar 48
epk kaolin 32
spodumene 36
red art clay 12
whiting 4
Marian
Fort Worth, TX
www.neon-cat.com/neon-cat_ceramics
Sabri Justin Douglas Ben-Achour on tue 8 jan 08
I've had the exact same problem. =20
Here are some reasons it happens and some info i've learned about Shinos fr=
om clayart and other readings:
1. John Britt, here and in his book, has talked about how excessive reducti=
on can turn shino green. That's been born out by what we've seen with our =
kiln, and by the chemistry of iron in glazes. When in low concentrations o=
r reduced (by the kiln atmosphere or certain other compounds in the glaze -=
oxides of calcium, titanium too apparently), Iron dissolves in the glass a=
nd turns it green (sometimes brownish). When not reduced heavily, the iron=
will crystallize out and turn some shade of red or black depending on cool=
ing. =20
How to fix: green comes from too heavy reduction. stop reducing so much.=20
lay off the reduction towards the end of the firing. you don't need a sup=
er-heavy reduction at that time. and, to deposit soot on the pots you don'=
t necessarily need a heavy reduction mode - we have found that a neutral fl=
ame does the job just fine - you can watch through the peep holes with a fl=
ash light and see the soot developing. but, so you know, soda ash melts at=
around 1570F, which is cone 013/012, so if you want to do a heavy reductio=
n at around then, it won't hurt and maybe it will help for your particular =
kiln. soda ash will turn to soda (sodium oxide) at 1830F. What we do is a=
heavy body reduction for 40 minutes/3cone of temp change at around cones 0=
5-03 (1900F). Normally, we would have a half hour glaze reduction towards =
the end once cone 9 hits, but we have found that if we omit that glaze redu=
ction, we have much less of a problem with shinos turning green and nasty. =
=20
in my experience, you can get carbon trapping and still get the same snot g=
reen, just covered up with some black. it's the soda ash on the surface th=
at makes iron more susceptible to getting reduced. why/how that happens is=
something i'm still trying to learn about and will let you know once i've =
found concrete answers.=20
2. I've learned from several people that thickness of application has a gre=
at deal to do with color in shinos. thicker is more likely to go green, th=
inner is associated with oranges. This has to do with diffusion rates thro=
ugh the layer of glaze - but I don't know much more than that. It's probab=
ly a matter of Oxygen reoxidizing the iron on cool down, and not being able=
to diffuse in as well through a big fat glaze layer. but don't take my wo=
rd on that. =20
3. I think it was Frank Murrow who mentioned before how the red color of s=
hinos appeared during cool down. that would make sense (high temperatures =
will decompose Fe2O3 into some FeO (black/dark), if it's cooled fast it wil=
l be 'frozen' that way, if it's cooled slow you get Fe2O3 which is orange/r=
ed). =20
4. the longer you wait before firing, the more surface area has soda ash is=
deposited on it, the greater the capacity for it to melt and dissolve the =
soot into the glaze, and so the greater the capacity for carbon trapping. =
I say 'capacity' because if the soot isn't deposited at the right time, the=
n it won't matter how much soda ash you have on there. when people say th=
at you get better Carbon trap results from firing them immediately, they ar=
e probably referring to the interesting 'bloom' patterns you get when a pot=
is fired before all the soda ash has effloresced onto the surface of the g=
laze. You can get very nice floral patterns because the soda ash has only =
peeked through to the surface in certain areas, whereas if you wait several=
weeks the deposition of the carbon is more dependent on the flame (i.e. yo=
u could get a jet black pot, potentially). =20
ok hope this helps! let us know if you are able to fix the problem!
Sabri
www.thesabritree.com
> 29. Shino Carbon Trapping--Once & For All (6)
> Date: Mon, 7 Jan 2008 12:18:16 -0500
> From: Teri Hannigan=20
> Subject: Shino Carbon Trapping--Once & For All
>
> I've been trying to find consistent information on Carbon trapping with s=
hinos so that I can
> understand why we're having such a problem achieving good CT results at o=
ur community college
> studio.
>
> Our attempts at carbon trapping often result in a weird green. Where wax =
has been applied to the
> surface, it's a firey orange with a shimmery gold halo. Great, but otherw=
ise no blackish grey
> indicating carbon trapping--only what has been described in this forum as=
"snot green," which
> perfectly describes what we're getting. Hey, I have nothing against puke =
(or snot) green, but
> that's not the carbon trapping I long for. I've searched and researched t=
he internet, including this
> forum and in books and magazines, but can't find the information I seek. =
Hoping to find
> answers, I'm desperately seeking articles on carbon trapping from an old =
issue of Studio Potter.
> Without success--this back issue is out-of-print (below).
>
> Here's what's consistent in our community college studio:
> -Claybody=3DB-mix/w/sand
> -Shinos used for CT contain about 17% soda ash and some iron content; app=
lied to bisqued ware
> -Reduction starts at cone 08 and continues throughout for the copper reds=
to cone 10
>
> Here's why I'm so confused and remain such an ignoramus on the subject:
> 1. Some say let shino-glazed ware sit (up to 2 weeks!) before firing so s=
odium crystals develop on
> the surface; others say fire immediately for best CT results.
> 2. Most experts say to start reduction early in the firing cycle, but the=
ir answers range from cone
> 010-cone 014. I understand that soda ash melts at a relatively low temper=
ature, 1550 degees F,
> so it makes sense to start reduction before that. But when, exactly?
> 3. Some say reduction, as measured by an oxyprobe reading of 70-80, say, =
doesn't necessarily
> mean soot (carbon) is being developed on ware inside the kiln. They say t=
hat the best indication
> of carbon development is smoke (soot) emanating from the peep holes and d=
oor cracks. Whew!
> Not a good time to be in the kiln room, and I hope the kids from OSHA don=
't mind! I've been
> further cautioned that there shouldn't be any increase in kiln temperatur=
e while soot is being
> developed. Otherwise, the carbon will "burn off" before the soda ash melt=
s. Unfortunately, our
> kilns have no pyrometers, nor do we own an oxyprobe. Firings are done wit=
h several cone packs
> (9,10, 11 and 08, 09, 010) We're installing 2 new Geil kilns (+ pyrometer=
s) this summer, so
> hopefully we'll be able to control firings more scientifically. Is an oxy=
probe helpful for carbon
> trapping?
> 3. Some say reduce all the way through the firing--if you oxidize after d=
evelopment of carbon
> that the carbon will burn out and defeat any efforts at carbon trapping. =
Others say reduce hard
> and early for an hour or so then gradually switch to neutral or oxidation=
at the end.
> 4. Some say that the weird green is due to enough reduction for iron to t=
urn green in the glaze,
> but not enough soot (carbon) deposited on the surface before the soda ash=
melts. I've wondered
> if that "ashy" green color we've gotten is from the carbon, in the form o=
f ash, merging with the
> melting soda ash due to not reducing (creating carbon) before the soda as=
h has a chance to melt
> and "trap" the carbon.
> 5. Some say you can't fire copper reds in the same kiln as CT shino, but =
I haven't been able to
> discern what the problems are and why--especially if the soda ash has alr=
eady melted and
> vitrified, trapping the carbon beneath.
>
> Tony, Sheila, Steve, Judith, Matt, Liz, Shirley, Harvey and last
> but certainly not least, Malcolm--and anyone else I've left out--Help!
> I'mobsessed!
>
> No Longer Available:
> Studio Potter issue 30 #2 (June 2002)
> CARBON-TRAPPING ALONG THE OLD SHINO TRAIL
> CONFESSIONS OF A CARBON-TRAPPER by Malcolm Davis
> MY SECRET LIFE AS A SHINO ADDICT AND CARBONTRAPPER by Harvey Sadow
> TWO BOWLS by Shirley Johnson
> MOVING FORWARD by Liz Willoughby
> CARBON- TRAP: HOW AND WHY by Matt Long
> CARBON-TRAP SHINO by Judith Duff
> CARBON-TRAPPING SHINO GLAZE by Steve Loucks
> THE GHOST OF CARBON PAST by Tony and Sheila Clennell
_________________________________________________________________
Share life as it happens with the new Windows Live.
http://www.windowslive.com/share.html?ocid=3DTXT_TAGHM_Wave2_sharelife_0120=
08=
Lee Love on tue 8 jan 08
I get carbon trapping when I don't want it in shinos with 6% soda
ash in them. You might try backing off the soda ash from 16% to
avoid the snot green.. Try a line blend from 5% to 17%. Do you
use Neph Sye or a soda feldspar? Maybe these do not need as much
soda ash? A friend of mine Euan Craig, gets carbon trapping in his
woodfired soda kiln on unglazed porcelain.
Not having total control of shinos is the nature of the beast.
Even Master M. Davis says he can't control carbon trapping.
--
Lee in Mashiko, Japan
http://groups.google.com/group/ClayCraft
"Men are born ignorant, not stupid. They are made stupid by
education." -- Bertrand Russell
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