Hodaka Hasebe on wed 24 apr 96
I am interested to try "Tanka" (reduction cooling ?) with a gas kiln. All
I know is to fire to cone 9-10, and reduce down to 1650-1750F with fire
overflowing from a burner port. (Or, In Japan, they put a raw wood into a
kiln through a special entrance and closed up after cone 9-10.) This
process makes clay body reduce heavily and traps many carbon to glaze.
Does anyone know the process in details ? Should I close damper completely
? (I assume not) Should I use a pilot burner or a burner ? How heavy
should I reduce? How much smoke should I expect in the kiln room ? etc.
I bought a 21' splash pan designed for the master series, which fit to my
old Shimpo wheel (RK series), at NCECA. I do not have any problems for
throwing due to the size, and it works well if you trim a lot (my floor is
very much clean since) and use one type of clay. It would be difficult to
clean up the pan completely if it is wet without removing it, though.
Hodaka Hasebe Hasebeh@vivanet.com
Darrol F. Shillingburg on wed 4 sep 96
Hi,
New to ClayArt, but not to clay or art or much else!!
Heard about "reduction cooling" from John Neely during a visit to The
Appalachian Center for Crafts this summer. Upon retrun home my first kiln load
turned a beautiful metalic black, (thanks John), the second a strange tan with
yellowish overtones. 'I am a converted painter.'
I "froze" the propane tank on the first kiln load so " no data".
The question is , "What cone temperatures do I need to fire to, how much body
reduction and at what temperatures?" ( I am able to do reduction firing) I
reduced the first kiln load with a yellow flame burning during "cooling" until
the wares "turned dark". OK, so it's not scientific, but I am a 'converted
painter'
I fire again tomorrow. Any suggestions would be appreciated!
Darrol
P.O.Box 1054
Elephant Butte
NM 87935
505/74-5143
CIS 74353,2316
Frederic Allen Herbst on mon 3 nov 97
I've read and heard a few things about reduction cooling ware from high
fire temps (reaching temp and continuing to fire on the way down). Does
anyone have practical advice about this method? How long and what temp
range do I fire down to? What clays and glaze types work the best?
Thanks for the help.
Frederic Herbst
(busy experimenting with everything I can while I'm still in grad
school)
fah0001@jove.acs.unt.edu
JOHN NEELY on wed 5 nov 97
Frederic Allen Herbst wrote:
> I've read and heard a few things about reduction cooling ware from
> high fire temps (reaching temp and continuing to fire on the way
> down). Does anyone have practical advice about this method? How long
> and what temp range do I fire down to?
Oldtimers on Clayart will recognize this as a topic that comes up
periodically. You'll forgive me if I quote earlier posts...
> Without going into all of the variables, a basic firing schedule to
> start with would with would be the one that I use most - reduction
> sufficient to stall the kiln at cone 08-04 range for about 45
> minutes, light reduction up to top temperature of cone ten, and heavy
> reduction down to about 800 degrees centigrade. Then the burners are
> turned off and cooling to room temperature is with no manipulation of
> atmosphere. Need I add that it takes very little gas to keep the kiln
> reducing while it cools to 800?
>
FWIW, all my initial tests on this were cone with a pyrometer that read in
centigrade. 800 C is actually about 1472 F but I often use the figure of
1450 F as a benchmark.
For example, in another post I wrote:
> Reduction cooling....... relies on carbon monoxide (not
> carbon!) produced by a small reducing flame in the kiln as it cools.
> If the clay and glaze have been reduced on the way up, reduction
> cooling prevents reoxidation. If the firing has been in oxidation,
> the reducing flame will affect only the surface. Either can produce
> interesting results with some clays and glazes; I usually use the
> former procedure. Incidentally, most clays will still be reactive at
> 1750; to insure that there is no reoxidation, I fire down to 1450.
> How much you open the damper, what burner you use, etc. depends
> entirely on your kiln - how tight it is, whether you have sealed
> burners, etc. Smoke is certainly not necessary - carbon monoxide is a
> colorless gas.
>A pyrometer really helps here. The problem with using cones to gauge the
>cooling is that is very difficult to get them to stand back up as the
>temperature decreases. (g)
Frederic Herbst goes on to ask:
> What clays and glaze types work the best? Thanks for the help.
>
> Frederic Herbst
>
> (busy experimenting with everything I can while I'm still in grad
> school)
The basic idea is to use something that contains iron or copper. For clay just
about anything other than very white porcelain will work - when I do workshops
on the subject I start students out with standard stoneware bodies. Break open
some pieces fired in standard reduction firing to see what kind of texture and
color they show. Progressively increase some iron bearing clay while
decreasing some of the other fluxes.
Glazes that are solution colors are not nearly as interesting as ones that are
colored by crystals in the glaze - standard example is iron red or persimmon.
Matte copper glazes are interesting, too.
John Neely
Utah State University
Ash Pot on mon 25 jul 11
Im getting ready to fire the Manabigama next week and thinking about Reduct=
=3D
ion Cooling. I was thinking about reducing till about 1600 F. I have not be=
=3D
en able to see pots on the web that have been fired in a Reduction Cooled k=
=3D
iln. Any one know of any to see?
thanks=3D20
Mark
lookoutmountainpottery.com
John Britt on mon 25 jul 11
Mark,
Type this into Google and then click Images: "reduction cooling utah woo=
=3D
d firing"
All the reduction cooling you can ask for!
johnbrittpottery.com
Karen Sullivan on tue 26 jul 11
John Neely would fire his gas kiln
with reduction cooling...
as the kiln cools he would light it
and reduce a couple of minutes
as the kiln moved down
the cooling cycle.
google him for images
I flash my kiln for bright
copper reds by reducing the kiln
after it has cooled to red heat...
I reduce for a few minutes...
then let it cool entirely.
it's terrifying because there is
a lot of noise in the kiln...crunching
sounds...
the charcoal kiln has so much charcoal
in the chamber/saggar...it cools
in a reducing atmosphere...so
the work comes out very dark.
I let the kiln cool for a couple of
days...and shovel out a lot of
ash...some still glowing red.
seems I heard a story of
someone thinking they could cool
the kiln by turning on the blowers...
the air caused the kiln to climb
in temp...
so the long story is the process
of charcoal firing
was discovered by someone who worked
on a wood kiln in Japan...the master
potter would place his favorite
pieces in the firebox where they
would get buried with charcoal...
so that is what one is going for in
the charcoal firing...with the use of gas
to reach temp...an effort to
duplicate the fire box of a wood kiln.
hope that helps
karen
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