David Donica on wed 5 feb 97
As a largely self-taught potter I am always amazed and somewhat chagrined
in regards to my gaps in knowledge but I just keep trying to shovel
information in and learn it all (ha ha). Anyway, the latest is that I want
to bisque fire in my new propane fired updraft kiln. For the past 17 years
I've only fired in a Skutt electric because that's what I learned with and
it was so easy to just put the pots in there and plop a cone in the kiln
sitter. Well, the Skutt is biting the dust. It's demise was facilitated
by the fact that about 8 years ago during a protracted home building
experience my (ex) husband somehow managed to step on the edge of the
pallet my kiln was being stored on and launch the top ring (yes the one
with the lid) off of our hillside homesite. You can imagine my horror as I
watched the ring careen down the hill, crash into a pine tree and basically
explode into a zillion pieces. Anyway, back to the issue at hand. I've
also been having problems with pinholing and want to do this right so I
don't have to face the another load of crummy pots. So, the questions are-
1. How many pots can I stack together? 3 soup bowls, 6? How many plates?
2. How long do I candle? Do I candle all 7 burners or just one?
3. Do I leave the door cracked open or is the peeps and damper enough?
4. What cone should I bisque to? (I glaze fire to ^10). I went from 07 to
05 in
my electric in order to eliminate the pinholes but it didn't help.
5. Should I depend on my pyrometer which is mounted in the center of the back
wall of the kiln or cones, or both?
6. How long should the entire bisque take (including candling time) and what
rate of temp. gain should I maintain? I know there are lots of variables
but
basically I make dinnerware and no thick pieces.
7. Is there anything else I should know about doing a bisque in a gas kiln vs.
electric? Is one considered "better" than the other?
Hey, many thanks. I will be eternally grateful for any information anyone
has to share. Maggie in Mt. Shasta where we're all hoping for a big snowstorm.
Maggie Shepard
FireWorks Pottery
Mt. Shasta, Calif.
Ellen Baker on thu 6 feb 97
I bisque about 99% of my work in my gas kiln, and I have no problems
whatsoever. Basically, load the way you would in an electric kiln. But as
in all [gas] firing, be sure to allow for good airflow throughout the load.
I always preheat my kiln -- ware and shelves evenly warmed -- before I
light the main burners. I like to be sure that there are no "damp pockets"
under the feet of green pots, and I feel better knowing that the soft brick
is dry before I start-up.
Be sure to fire very, very slowly through about 300-400F, and only just a
little less slowly to 1000F -- at which time you can "giv'er the spur" to
06 or whatever bisque you prefer. Lastly, do remember to keep the firing
as clean an oxidation firing as you can -- burner supply air wide open,
damper open.
I suggest that you learn as much as possible about your kiln's firing
characteristics by using LOTS of WITNESS CONES, even during the bisque.
You may find that at higher, glaze temperatures (at ^10) the
characteristics are very different -- but you'll never know how different
from a heat-work perspective, unless you make a deliberate study using
cones.
If you want to get into more detail, you're welcome to contact me directly
at orion@telcomplus.com. Regards, Ellen Baker.
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>
> ----------------------------Original message----------------------------
> As a largely self-taught potter I am always amazed and somewhat chagrined
> in regards to my gaps in knowledge but I just keep trying to shovel
> information in and learn it all (ha ha). Anyway, the latest is that I
want
> to bisque fire in my new propane fired updraft kiln. For the past 17
years
> I've only fired in a Skutt electric because that's what I learned with and
> it was so easy to just put the pots in there and plop a cone in the kiln
> sitter. Well, the Skutt is biting the dust. It's demise was facilitated
> by the fact that about 8 years ago during a protracted home building
> experience my (ex) husband somehow managed to step on the edge of the
> pallet my kiln was being stored on and launch the top ring (yes the one
> with the lid) off of our hillside homesite. You can imagine my horror as
I
> watched the ring careen down the hill, crash into a pine tree and
basically
> explode into a zillion pieces. Anyway, back to the issue at hand. I've
> also been having problems with pinholing and want to do this right so I
> don't have to face the another load of crummy pots. So, the questions are-
> 1. How many pots can I stack together? 3 soup bowls, 6? How many plates?
> 2. How long do I candle? Do I candle all 7 burners or just one?
> 3. Do I leave the door cracked open or is the peeps and damper enough?
> 4. What cone should I bisque to? (I glaze fire to ^10). I went from 07 to
> 05 in
> my electric in order to eliminate the pinholes but it didn't help.
> 5. Should I depend on my pyrometer which is mounted in the center of the
back
> wall of the kiln or cones, or both?
> 6. How long should the entire bisque take (including candling time) and
what
> rate of temp. gain should I maintain? I know there are lots of
variables
> but
> basically I make dinnerware and no thick pieces.
> 7. Is there anything else I should know about doing a bisque in a gas
kiln vs.
> electric? Is one considered "better" than the other?
>
> Hey, many thanks. I will be eternally grateful for any information anyone
> has to share. Maggie in Mt. Shasta where we're all hoping for a big
snowstorm.
> Maggie Shepard
> FireWorks Pottery
> Mt. Shasta, Calif.
>
Ron Roy on fri 7 feb 97
I've
>also been having problems with pinholing and want to do this right so I
>don't have to face the another load of crummy pots. So, the questions are-
>1. How many pots can I stack together? 3 soup bowls, 6? How many plates?
>2. How long do I candle? Do I candle all 7 burners or just one?
>3. Do I leave the door cracked open or is the peeps and damper enough?
>4. What cone should I bisque to? (I glaze fire to ^10). I went from 07 to
>05 in
> my electric in order to eliminate the pinholes but it didn't help.
>5. Should I depend on my pyrometer which is mounted in the center of the back
> wall of the kiln or cones, or both?
>6. How long should the entire bisque take (including candling time) and what
> rate of temp. gain should I maintain? I know there are lots of variables
>but
> basically I make dinnerware and no thick pieces.
>7. Is there anything else I should know about doing a bisque in a gas kiln vs.
> electric? Is one considered "better" than the other?
>
>Hey, many thanks. I will be eternally grateful for any information anyone
>has to share. Maggie in Mt. Shasta where we're all hoping for a big snowstorm.
>Maggie Shepard
>FireWorks Pottery
>Mt. Shasta, Calif.
Hi Maggie,
I have always bisqued in my gas kiln so here are my suggestions
Stack as tight as you like but fire slow. Make sure your burners and the
atmosphere in your kiln are strictly oxidizing between 500C and 900C. I
usually say 700C to 900C but there may be temperature gradients in your
kiln depending how it is designed.
Keep the rate of climb during that phase to 50C per hour.
I have always fire my bisque to cone 04. If you don't mind the occasional
dunt on larger items you could go lower but whats the point.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
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