Geminison@AOL.COM on tue 16 jan 01
I have an electric kiln and have very little experience with one. I am not
able to use a venting system, so I would like to know the recommendation for:
1. bisque firing - how long must I leave lid open? Can I close all peep
holes after reaching red heat (1100 degress or above)?
2. Similar question about glaze firing - how and when do I close or leave
peep holes open, etc.
Thanks so much,
Sonny F
Charles Moore on tue 16 jan 01
Sonny,
When I was forced to shift from gas to electric firing, I got a copy of
Richard Zakin's book _Electric Kiln Ceramics: A Potter's Guide to Clays and
Glazes_. It is an excellent guide and provides guidelines for both bisque
and glaze firings.
Charles Moore
Sacramento, CA
----- Original Message -----
From:
To:
Sent: Monday, January 15, 2001 9:00 PM
Subject: Kiln Oxidising
> I have an electric kiln and have very little experience with one. I am
not
> able to use a venting system, so I would like to know the recommendation
for:
> 1. bisque firing - how long must I leave lid open? Can I close all peep
> holes after reaching red heat (1100 degress or above)?
> 2. Similar question about glaze firing - how and when do I close or leave
> peep holes open, etc.
> Thanks so much,
> Sonny F
>
>
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Cindy Strnad on tue 16 jan 01
Hi, Sonny.
First, you might want to write to the manufacturer of your kiln and request
a manual. That's usually helpful, though not always helpful enough.
There's a lot on this in the Clayart archives, including messages I've
written myself, and I recommend you search it out. Firing is a lot more
complex than I realized when I started, and I blew up a lot of pots finding
this little fact out.
Without knowing anything about your kiln or your making/firing methods, it's
difficult to give you any specifics as to when you should close the peep
holes, but really, that's the least of your worries. There's a lot more to
learn than that.
That said, get a small mirror, keep it at the kiln room ambient temperature.
Hold it over the peephole during your bisque firing and see if it gets
steamed up. If it does, there's still moisture being released and you should
leave the peepholes open. Once the mirror remains dry, you can close the
peeps. You should fire bisqueware very slowly up to this point, because
rapid heating can cause it to crack and/or explode due to the moisture
content in even bone-dry clay.
For glaze, I keep the peeps open and the lid open a crack until all the
paraffin burns off, and then shut it down. I use paraffin to wax the bases
of many of my pots. If I'm firing a load which hasn't required any waxing
and contains no volatile substances, I start it out with the peeps and the
lid closed. It's particularly important (for glaze appearance) to fire glaze
slowly toward the end of the glaze firing process.
If your kiln is in, or under a living or working space which will be
occupied during the firing cycle and at any time before the fumes can seep
out, you must ventilate it for the safety of the people who will be present.
It can be done, it's just that it can sometimes be expensive. If it can't be
done, then the kiln needs to be moved elsewhere. Otherwise, you expose
people to significant health dangers, even if you can't smell anything nasty
coming from the kiln.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Maggie Woodhead on fri 19 jan 01
Hi Sonny and Kia Ora,
The following are the schedules I use in
my electric kiln for firing bisque and glaze. A lot of problems disappeared when
I moved to using these. I fire using Celsius.
1 Bisque - No bungs in at any time for this firing.
50o ramp to 50o then hold for 3 hours or switch off and leave overnight.
The lid may be raised at some point to allow moisture out. This is to
ensure the pots are dry and should avoid breakage from firing too soon
Then 50o ramp to 200o and a 60 minute soak
100o ramp to final temp mine is about 920o then 60 min soak
I have an outside pottery and leave the windows open for fumes to escape and
never work in the pottery while the kiln is firing.
2. Glaze firing - Fire without bungs until just below 600o then put them in for
the rest of the firing.
100o ramp to 100o then soak 20mins or so depends on the size of the kiln
my test kiln I only give 10 mins but the 5.5 cubic foot I give more and then too
depends on how tightly stacked it is.
100o to 600o then soak approx 30mins
150o to 1260o (check with a cone periodically) then 60 minute soak.
I always fire at night but having a digital controller makes this a breeze,
there will be some adjustments to get exactly the right schedule for your kiln
but these rates made a big difference to me and they came from a potter with a
lot of commercial experience.
Good luck with your firings,
----Best Wishes Maggie----
maggiew@clear.net.nz
:
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