primalmommy on wed 7 apr 04
In the winter months, and with my studio undergoing renovation, I have
gotten into the habit of bringing home class projects (scout groups,
homeschoolers, whatever) and putting them directly on a kiln shelf. This
is generally thick walled work, but doesn't need to be fired/returned
for a few weeks, so I let it dry in there, layer by layer.
Is it a really bad idea to let the inside of a big electric kiln get a
bit damp? It's been cold and rainy, and the pots in there have not dried
much in the last week... i turned it on low with the lid up this
afternoon to nudge them along, but i wonder whether the damp is bad for
the elements.
Kiln gurus? what say ye?
yours,
Kelly in Ohio
Kelly Averill Savino
http://www.primalpotter.com
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Vince Pitelka on thu 8 apr 04
Arnold Howard wrote:
> At Paragon we've always said that the ware should be bone-dry before
placing
> it inside the kiln. If the ware is moist, the kiln uses electric power to
> turn that moisture to steam. It's an expensive way to dry ware.
Arnold -
You are certainly one of the experts when it comes to electric kilns, and I
know we all appreciate your generous contributions to this list. But I have
to question the above. I would agree that it is always far better to let
the work get bone dry before loading the bisque. But if you have a load of
damp wares that you need to get bisque fired, running the kiln overnight
with the lid ajar and the bottom element on low is a very practical and
inexpensive way to dry the wares and meet the deadline.
I would also say that any corrosion caused by initial evaporation of water
from damp wares is of little concern in comparison to the corrosion caused
by the sulfur and chemically-combined water given off during the
water-smoking period of a bisque firing, when things are HOT and oxidation
is supercharged.
We have some 7-cu. ft. toploaders from one of your competitors, and they
have been in heavy service here for 20 years. They are used mostly for
bisque firing, occasionally for low-fire glaze. Over the years we have
replaced lots of those hex-washer-head sheet metal screws and Kiln-Sitter
mounting screws , but otherwise we get good element life, and they have the
original hinges, switch boxes, handles, etc. We frequently fire damp wares
in these kilns, and corrosion has not been a problem.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Arnold Howard on thu 8 apr 04
At Paragon we've always said that the ware should be bone-dry before placing
it inside the kiln. If the ware is moist, the kiln uses electric power to
turn that moisture to steam. It's an expensive way to dry ware.
If you leave the lid well vented or leave a downdraft vent turned on during
candling, you can get away with using the kiln to dry the ware. But you will
probably increase the corrosion of steel parts in the kiln especially if
moisture is still in the ware as the temperature goes up past candling.
One of the signs that the ware was too wet is water dripping from the kiln's
stainless steel case. Another sign is that the kiln takes a long time to
fire. It struggles to burn off the moisture. Sometimes it is unavoidable to
fire moist greenware. But if possible, the ware should be bone-dry.
Sincerely,
Arnold Howard
Paragon Industries, L.P.
arnoldhoward@att.net
From: "primalmommy"
> Is it a really bad idea to let the inside of a big electric kiln get a
> bit damp? It's been cold and rainy, and the pots in there have not dried
> much in the last week... i turned it on low with the lid up this
> afternoon to nudge them along, but i wonder whether the damp is bad for
> the elements.
> Kelly in Ohio
Snail Scott on thu 8 apr 04
At 08:13 PM 4/7/04 -0700, you wrote:
>Is it a really bad idea to let the inside of a big electric kiln get a
>bit damp?
Maybe a little, but not much. I think moisture is
more harmful to the electrical connections in the
control box on the outside, and that's got nothing
to do with what you put inside.
I often load my work while leather-hard, since it's
strongest then. I also don't have the space to let
finished green work sit around the studio, getting
bumped into while it dries, especially while there's
perfectly good empty space inside the kiln!
My kiln lives outdoors (in the desert, but it does
rain and snow here,) and the previous owner kept
it outside, too. The control box has noticeable
rust on the steel and green corrosion on the copper
wiring, but the inside shows no deterioration that
I can attribute to moisture.
I don't usually fire the stuff 'til it's dry, but
if I lived in a damp climate, I might be tempted.
-Snail
Ivor and Olive Lewis on fri 9 apr 04
Dear Kelly,
At normal temperatures water or water vapour will have no effect on
your kiln elements.
But at elevated temperatures, especially above 1050=BA C water vapour,
really superheated steam, can cause problems with some metals and you
might get accelerated corrosion.
Searching the old grey matter, I recall Hydrogen can be prepared by
passing steam over red hot Iron Powder or Iron Wool. The solid residue
will be Iron Oxide.
If water from the pots collects in the insulation then it might be a
problem unless you dry the kiln out before firing.
Best regards,
Ivor Lewis. Redhill, South Australia
Jen Baumeister on fri 9 apr 04
You could try this method on those damp days....the day before loading my
kiln for bisque firing I put a
very small electric heater (with a fan ) aimed from a fair distance at my
drying rack. As the pots on the rack are
already quite dry this method seems to just take the dampness out...
I have a frontloading kiln and have used this method with the green ware in
the kiln and the door fully open.
With the air circulation the moisture does not sit in the kiln.
I'm not sure what the difference in power usage is compared to using the
kiln's "preheat"
but with the heaters air circulation I end up with a nice, warm, less damp
work space in my tiny studio.
Cheers,
Jen
John Britt on fri 9 apr 04
I have always used the bottom element on low with the lid ajar. This heats
up the air and it rises out the kiln heating the other shelves on the
way. This also creates a nice natural drafts as I leave all the spies
out.
Using the top element will allow most of the heat to leave without being
absorbed by the other pots as it exits the kiln.
Hope that helps,
John Britt
Snail Scott on fri 9 apr 04
At 07:35 PM 4/8/04 -0500, Vince wrote:
>...running the kiln overnight
>with the lid ajar and the bottom element on low is a very practical...
Vince-
I have always figured that the top of the
kiln would stay cool this way, causing a broad
temperature gradient from bottom to top,
and a sudden heat rise for the topmost clay
when the lid is finally shut. So, I generally
candle using the top elements only, figuring
that the enclosed bottom will trap heat and
warm up together with the heated (but open)
top.
In an enclosed space like a kiln, even with
the lid propped, I assume that radiant and
conductive heat are more relevant than
convection, which might normally draw heat
up and away, but 'weighting' the turned-on
elements toward the top of the kiln will
compensate for the heat loss at the open lid.
Thoughts?
-Snail
Arnold Howard on mon 12 apr 04
I agree with you, Vince. Candling the kiln with lid propped or even open all
the way is fine. The problem is in firing moist ware to higher temperatures.
That's when the moisture ends up dripping from the kiln's steel case. The
firing slows to a crawl.
Sincerely,
Arnold Howard
Paragon Industries, L.P.
arnoldhoward@att.net
From: "Vince Pitelka"
I would agree that it is always far better to let
> the work get bone dry before loading the bisque. But if you have a load
of
> damp wares that you need to get bisque fired, running the kiln overnight
> with the lid ajar and the bottom element on low is a very practical and
> inexpensive way to dry the wares and meet the deadline.
> - Vince
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