Carol Seidman on sun 7 mar 99
Fellow Clayarters:
I am using a small electric kiln (2.5 cu. ft. firing chamber) and
trying to get the most utility from each firing. I nest pieces to be
bisque fired with stilts separating them and have had great results.
Really pack them in. A good portion of my work is hand thrown,
handpainted earthenware, glazed with commercially prepared clear glaze.
My question is: could I mix bisque and glaze pieces in the same firing?
Would the gasses burned out from the bisque, affect the glazed ware,
firing to ^05?
I realize the chance I take that if one piece of bisque blows up, it
will ruin the entire load, but of all the mishaps in the studio, my
greenware behaves itself. The savings in firing space would be a great
advantage if I could nest a glazed bowl up on a stilt, inside a bowl to
be bisque fired. Thanks for your help. Carol Seidman
cseidman@home.com
Dayton, New Jersey
Richard Selfridge on mon 8 mar 99
The answer is yes you could try it but there are some downsides. Some
things to consider:
Do you think you can put glaze on the pieces that are "hard bisqued" to
cone 05? We bisque our majolica pieces (slowly at the end) to 06 and then
glaze fire them to 04.
Will the glaze fire be mature at 05?
Sometimes we need to refire the majolica (bad pinhole, or void or crawl)
and for this refiring, because we don't want the glaze to move it works
well to pop them in the next bisque. The little bit of glaze touch up melts
nicely at 06 and solves the problem. I assume that the outgassing of the
bisque does not affect the refired glaze.
All of this assumes that you use an extraction fan system like the
envirovent which keeps the outgassing moving out of the kiln. My guess is
that the outgassing from the bisque (sulpher and carbon from lignite) is
dirtier than the products from the glaze firing. Bright colour comes from a
clean oxidizing atmosphere. You might find that loading the bisque on the
bottom and the glaze on the top works best,(assuming fan on bottom).
The envirovent "should" stay on to the top of the firing and be left on
until the kiln cools for unloading. However these fans are so powerful that
on a smaller kiln they can cool it too fast at the top end. That is if the
kiln shuts off without a good top soak,(we only have kilnsitters)then the
"quick cool" can give an underfired (unhealed pinholes) firing.
Leaving the fan on until cool works well on the 42inch oval but on the
27inch round kiln I wired a 110 volt plug to the kiln sitter so that the
fan shuts off when the kiln does. I let it cool gradually for a couple of
hours and then plug it back into the wall socket.
The reason for this is to "evenly" cool the ware to lessen the chance of
dunting large plates on the way down. My assumption is that a constant
flow of air from top to bottom will keep the temp more even than letting it
"natural draft" and pull cold air past the edge of a large plate from a
"leak" such as the kiln sitter pipe. As others have stated here it helps to
deflect the top by putting an empty shelf on the top under the lid.
Now when I fire (and refire) the large plates I wad them to raise them off
the shelf so that air can circulate under them when they go thru quartz
inversion. Sometimes putting a few hard brick around the edges of these
plates helps keep their "rim" temp up as well. My refire success has
greatly improved since I started doing all this.
Hope this gives a few clues, Richard Selfridge
http://www.compusmart.ab.ca/selfridgAt 11:57 PM 3/7/99 EST, you wrote:
>----------------------------Original message----------------------------
>Fellow Clayarters:
> I am using a small electric kiln (2.5 cu. ft. firing chamber) and
>trying to get the most utility from each firing. I nest pieces to be
>bisque fired with stilts separating them and have had great results.
>Really pack them in. A good portion of my work is hand thrown,
>handpainted earthenware, glazed with commercially prepared clear glaze.
>My question is: could I mix bisque and glaze pieces in the same firing?
>Would the gasses burned out from the bisque, affect the glazed ware,
>firing to ^05?
>I realize the chance I take that if one piece of bisque blows up, it
>will ruin the entire load, but of all the mishaps in the studio, my
>greenware behaves itself. The savings in firing space would be a great
>advantage if I could nest a glazed bowl up on a stilt, inside a bowl to
>be bisque fired. Thanks for your help. Carol Seidman
>cseidman@home.com
>Dayton, New Jersey
>
>
eden@sover.net on mon 8 mar 99
Hiya Carol,
Seems like putting the two SO close together is really asking for the
trouble you outlined. I have, upon occasion, used the top part of my kiln
for refires and the bottom for bisq with never any noticeable downside. My
take is that you want to push the envelope beyond caution here. But
economics is a powerful motivator, and I sure would like to hear about it
if you do it!
Eleanora
At 11:57 PM 3/7/99 -0500, you wrote:
>----------------------------Original message----------------------------
>Fellow Clayarters:
> I am using a small electric kiln (2.5 cu. ft. firing chamber) and
>trying to get the most utility from each firing. I nest pieces to be
>bisque fired with stilts separating them and have had great results.
>Really pack them in. A good portion of my work is hand thrown,
>handpainted earthenware, glazed with commercially prepared clear glaze.
>My question is: could I mix bisque and glaze pieces in the same firing?
>Would the gasses burned out from the bisque, affect the glazed ware,
>firing to ^05?
>I realize the chance I take that if one piece of bisque blows up, it
>will ruin the entire load, but of all the mishaps in the studio, my
>greenware behaves itself. The savings in firing space would be a great
>advantage if I could nest a glazed bowl up on a stilt, inside a bowl to
>be bisque fired. Thanks for your help. Carol Seidman
>cseidman@home.com
>Dayton, New Jersey
>
Eleanora Eden 802 869-2003
Paradise Hill
Bellows Falls, VT 05101 eden@sover.net
Martin Howard on tue 9 mar 99
So far I have had no problems from using my kiln for mixed firings. As
the top is 2 cones hotter than the bottom, 1 against 02, I can pick and
choose the right position for a piece, whether bisque or glaze.
Actually, it tending to work out that there is a cycle of first bisque,
then a glaze firing, but I do not want to be tied to that as I fire for
a local school and another potter who does not yet have her kiln. Their
work could be either bisque or glaze; I have no means of telling.
Martin Howard
Webbs Cottage Pottery and Press
Woolpits Road, Great Saling
BRAINTREE
Essex CM7 5DZ
01371 850 423
araneajo@gn.apc.org
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