Barbara Mazur on thu 27 jun 96
Hi all,
I would appreciate any info. and suggested reading on carbon trap. I had
the good fortune of pulling a "knock my socks off" teapot out of the last
firing. The pattern on one side of the porcelain teapot created waves of
carbon that resemble the rings when a stone skips accross a pond. The
opposite side of the teapot has a large luminous carbon area with the
addition of carboned areas that look like large freckles. The spout and
handle are a combination of both sides! And, the underside of the teapot
( there are short feet on this teapot, so I glazed the underside too) is
a mass of tight freckles! This was a c. 9 1/2 firing in a MFT that fires
uneven, has hot spots, cold spots. Many of the pieces in this kiln were
also glazed in the same carbon trap glaze. All pieces were dipped once.
The irony is that some pieces developed light carbon in areas, some heavy
in areas, and others developed no carbon markings at all! I don't know
or understand why. The irony is that although they were placed in
numerous areas throughout the kiln, the location of one piece to the next
did not effect the action of the carbon. Right next to this teapot, were
two mugs that were simply orange! Help please!
Barbara Mazur
South Florida
Barbara Mazur
barbaram@bcfreenet.seflin.lib.fl.us
Kelley M. Dean on sat 29 jun 96
At our studio we just discovered a glaze called CArbon Trap Shino out of
Ceramics Monthly, Unfortunately I don't have the recipe in front of me, but
it sounds like you already have a similar glaze. The secret is to sift wood
ash onto the still wet glaze and then fire it, you get beautiful markings
and drips, orange where it is thinner and a lustrous sheenall over the pot.
Give it a try.
>----------------------------Original message----------------------------
>Hi all,
>I would appreciate any info. and suggested reading on carbon trap. I had
>the good fortune of pulling a "knock my socks off" teapot out of the last
>firing. The pattern on one side of the porcelain teapot created waves of
>carbon that resemble the rings when a stone skips accross a pond. The
>opposite side of the teapot has a large luminous carbon area with the
>addition of carboned areas that look like large freckles. The spout and
>handle are a combination of both sides! And, the underside of the teapot
>( there are short feet on this teapot, so I glazed the underside too) is
>a mass of tight freckles! This was a c. 9 1/2 firing in a MFT that fires
>uneven, has hot spots, cold spots. Many of the pieces in this kiln were
>also glazed in the same carbon trap glaze. All pieces were dipped once.
>The irony is that some pieces developed light carbon in areas, some heavy
>in areas, and others developed no carbon markings at all! I don't know
>or understand why. The irony is that although they were placed in
>numerous areas throughout the kiln, the location of one piece to the next
>did not effect the action of the carbon. Right next to this teapot, were
>two mugs that were simply orange! Help please!
>Barbara Mazur
>South Florida
>
>Barbara Mazur
>barbaram@bcfreenet.seflin.lib.fl.us
>
>
Barbara Mazur on mon 1 jul 96
Hi Kelly and all,
I read that article too and that is the recipe I used..... w/o additional
wood ash added to the pot. I still would like to understand more about
the patterns (why / how), esp. because there were no additions to the
single dip. Can anyone help?
Thanks,
Barbara
Barbara Mazur
barbaram@bcfreenet.seflin.lib.fl.us
Richard Burkett on mon 1 jul 96
Okay, Barbara, I'll make a quick stab at why carbon trap makes the patterns
that it does. You've got a number of somewhat random (at least difficult to
predict) events that enter into this: flame paths, amount of reduction,
temperature when reduction is started, atmosphere before the reduction begins,
thickness of ware, thickness of glaze, and probably a few more that I haven't
thought of before my morning cup of coffee.
As I understand it, these glazes trap carbon when the glaze surface melts first
leaving carbon-containing compounds in the unmelted glaze below. When that
finally melts the carbon (a very refractory material as long as there's no
oxygen around to turn it into carbon dioxide) remains as particles within the
glass. (there should have been a comma after "finally melts," as the carbon
does not melt - the glaze does). Typically this type of glaze includes soda
ash or other soluble alkaline fluxes which will migrate to the surface of the
raw glaze as it dries, forming a crust of alkalies which will melt earlier than
the rest of the glaze, thus facilitating the carbon trapping. Thickness of the
bisqueware and the glaze will make variations in how fast the wet glaze dries
on the pot, and how the alkalies migrate and where the crust forms. You might
look at the piece with this in mind. Applying wax to the damp glaze might also
affect this - you might give this a try, it's just speculation on my part, but
sealing the surface with wax would prevent alkalie build up in those areas.
Time for coffee,
Richard
richard.burkett@sdsu.edu
Dave and Pat Eitel on tue 2 jul 96
>----------------------------Original message----------------------------
>Hi Kelly and all,
>I read that article too and that is the recipe I used..... w/o additional
>wood ash added to the pot. I still would like to understand more about
>the patterns (why / how), esp. because there were no additions to the
>single dip. Can anyone help?
>Thanks,
>Barbara
>
>
>Barbara Mazur
>barbaram@bcfreenet.seflin.lib.fl.us
My understanding of carbon trap is that in the very early stages of firing
when the flame is very low and giving off a lot of soot, that soot collects
on the pots. As the firing continues, the carbon trap glaze begins to melt
before the carbon sitting on the pots in the form of soot burns away. Thus
particles of carbon are trapped in the melted glaze and never burn away.
As for the patterns, that's a mystery to me--just the way I like it.
Later...Dave
Dave Eitel
Cedar Creek Pottery
Cedarburg, WI
daveitel@execpc.com
http://www.digivis.com/CedarCreek/home.html
Charles Mcgee (ART) on sat 26 apr 97
The question trapping has surfaced many times at the University of South
Florida, and I am still not satisfied withe the answers. What actually is
carbon trapping. Doesn't carbon burn out at 900 degrees and therefore
would not be evident in the glaze of a high fire vessel? Does it occur
at different temperatures for different clay bodies, or does it only
affect the glazes? Similar to a shino glaze is carbon trapping the cause
for the red orange/red blushes of wood fire ware? Can carbon trap
penetrate sagger? Thank you very much for any feedback, or directions
to a source of further information.
Chuck McGee
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