Maurice Weitman on mon 23 feb 04
Howdy,
Taking a moment to luxuriate in a dust-free, carpeted room (although
I love being in my garage, shlepping, demolishing, wiring, plumbing,
building, etc.) I thought I'd ask a related question.
I've seen folks begin firing a bisque load in an electric kiln with
the door cracked open for several hours, or overnight, even though
the kiln has a vent attached.
Why??? Is there any condition where this might be necessary? It
flies in the face of what I know about how and why these vents are
used.
I suppose it's possible that it would be desirable for higher rates
of air exchange during the early portions of the firing, but I'm not
sure about that, either.
What do you think?
Thanks.
Regards,
Maurice
Cindi Anderson on mon 23 feb 04
They probably don't know better. I've always had a vent and never fired
with a cracked lid in my life.
Cindi
----- Original Message -----
> I've seen folks begin firing a bisque load in an electric kiln with
> the door cracked open for several hours, or overnight, even though
> the kiln has a vent attached.
Arnold Howard on mon 23 feb 04
If you are using a downdraft vent (the type that removes air directly from
the kiln), the peepholes should be inserted and the lid closed all the way.
Otherwise the kiln interior will not have the negative pressure needed to
prevent fumes from entering the firing room.
If you are using an overhead vent, such as the one produced by Vent-a-Kiln,
then it is a good idea to vent the lid at the beginning of the firing.
Sincerely,
Arnold Howard
Paragon Industries, L.P.
arnoldhoward@att.net
From: "Maurice Weitman"
> I've seen folks begin firing a bisque load in an electric kiln with
> the door cracked open for several hours, or overnight, even though
> the kiln has a vent attached.
> Why??? Is there any condition where this might be necessary? > Maurice
Snail Scott on mon 23 feb 04
At 12:27 PM 2/23/04 -0800, you wrote:
>...I've seen folks begin firing a bisque load in an electric kiln with
>the door cracked open for several hours, or overnight, even though
>the kiln has a vent attached.
>
>Why??? Is there any condition where this might be necessary?
It's not to vent the kiln, it's to slow the rate
of heat rise. An electric kiln with the door
shut can warm up more quickly than is appropriate
for some work (especially thick work made of fine-
grained clay) even when firing on only one element.
Propping the lid isn't too energy-efficient, but
it is a simple and time-honored method of slower
candling.
-Snail
Maurice Weitman on mon 23 feb 04
At 15:44 -0800 on 2/23/04, Snail Scott wrote:
>It's not to vent the kiln, it's to slow the rate
>of heat rise. An electric kiln with the door
>shut can warm up more quickly than is appropriate
>for some work (especially thick work made of fine-
>grained clay) even when firing on only one element.
>Propping the lid isn't too energy-efficient, but
>it is a simple and time-honored method of slower
>candling.
Thanks, Snail. (and Arnold and Cindi)
I should have mentioned that the kilns are computer controlled, so
the issue of a too-brisk heat rise should be moot.
Regards,
Maurice
Ron Roy on tue 24 feb 04
Hi Maurice,
I still do that when drying clay (crack the lid) - with the controller set
to hold at 90C. I seem to think it will help the drying go faster. I should
qualify that though.
During the early stages of drying very wet pots it is best to have no
ventilation - so the kiln becomes like a dryer - and you get very even
drying with the humidity gradually lowering.
The next stage - when the ware is almost dry - then the vent - and or the
open lid will help dry faster.
When I test for moisture in the kiln I close up everything for 20 min -
then open both spys and hold something shiny at the top spy to see if there
is any moisture condencing there.
I don't think complete drying is crucial for thinly thrown ware but it sure
is for heavy work.
After the moisture is gone you can pretty well go as fast as you want. I
once screwed up a ramp and got to 700C in two hours - but after the load
was dried at 90C. There was no problem - not that I recommend that.
RR
This is not crucial for thinly thrown ware I don't think but it sure is for
heavy work.
>Taking a moment to luxuriate in a dust-free, carpeted room (although
>I love being in my garage, shlepping, demolishing, wiring, plumbing,
>building, etc.) I thought I'd ask a related question.
>
>I've seen folks begin firing a bisque load in an electric kiln with
>the door cracked open for several hours, or overnight, even though
>the kiln has a vent attached.
>
>Why??? Is there any condition where this might be necessary? It
>flies in the face of what I know about how and why these vents are
>used.
>
>I suppose it's possible that it would be desirable for higher rates
>of air exchange during the early portions of the firing, but I'm not
>sure about that, either.
>
>What do you think?
>
>Thanks.
>
>Regards,
>Maurice
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
| |
|
