Pfeiffer Fire Arts on tue 1 apr 08
We finally got an old small electric kiln up and running. Seems to work fine
but having not fired an electric before I did end up with a few questions
after reading a bit. One is I see lots of references to putting a mirror up
to the top vent and not going up in temp before the mirror does not fog up.
The problem is the mirror never stopped fogging up! After a few hours I went
and did a somewhat fast bisque firing as it was getting very late to start a
firing and all went very well. What did I do wrong? The kiln has a nice
small hole in the top that seemed the perfect place to do this but even up
to 800F it still fogged the mirror. The ware seem to be quite dry.
The other question is are all electric kiln elements the same? We turned
ours up on high and the top and bottom elements were bright red but the
middle two were much dimmer. My first guess is the middle two have not been
replaced but the outer two have been at some point in time.
Thanks,
Dan & Laurel in Elkmont Al
www.pfeifferFireArts.com
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Arnold Howard on tue 1 apr 08
From: "Pfeiffer Fire Arts"
are all electric kiln elements the same? We turned
> ours up on high and the top and bottom elements were
> bright red but the
> middle two were much dimmer. My first guess is the middle
> two have not been
> replaced but the outer two have been at some point in
> time.
--------------
Your kiln probably has "tuned" elements. The two areas in
the kiln that require the most heat are the top and bottom.
This is because the lid and bottom are large thermal masses.
To give those areas extra heat, the top and bottom elements
are designed to pull more wattage than the center elements.
This is why the top and bottom elements glow sooner than the
center elements.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
William & Susan Schran User on tue 1 apr 08
On 4/1/08 1:56 PM, "Pfeiffer Fire Arts" wrote:
> What did I do wrong? The kiln has a nice
> small hole in the top that seemed the perfect place to do this but even up
> to 800F it still fogged the mirror. The ware seem to be quite dry.
>
Nothing wrong, that's chemically combined water, previous to that is water
of absorption. And more than likely your thermocouple/pyrometer may not be
that accurate.
> The other question is are all electric kiln elements the same? We turned
> ours up on high and the top and bottom elements were bright red but the
> middle two were much dimmer. My first guess is the middle two have not been
> replaced but the outer two have been at some point in time.
Depends what kiln you're firing.
Some, such as L&L, use same elements top to bottom.
Others, such as Skutt, use different elements at top & bottom than in the
center, so the top & bottom may be glowing and the center ones will not.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Steve Slatin on tue 1 apr 08
How old was the kiln? How long since it was fired last? Fire brick
can absorb quite a bit of humidity; it may have been the kiln, and
not the ware that was releasing the humidity. -- Steve Slatin
Pfeiffer Fire Arts wrote:
We finally got an old small electric kiln up and running. Seems to work fine
but having not fired an electric before I did end up with a few questions
after reading a bit. One is I see lots of references to putting a mirror up
to the top vent and not going up in temp before the mirror does not fog up.
The problem is the mirror never stopped fogging up! After a few hours I went
and did a somewhat fast bisque firing as it was getting very late to start a
firing and all went very well. What did I do wrong? The kiln has a nice
small hole in the top that seemed the perfect place to do this but even up
to 800F it still fogged the mirror. The ware seem to be quite dry.
The other question is are all electric kiln elements the same? We turned
ours up on high and the top and bottom elements were bright red but the
middle two were much dimmer. My first guess is the middle two have not been
replaced but the outer two have been at some point in time.
Thanks,
Dan & Laurel in Elkmont Al
---------------------------------
You rock. That's why Blockbuster's offering you one month of Blockbuster Total Access, No Cost.
Bonnie Hellman on tue 1 apr 08
I can attest empirically that chemically combined water exists at least
until 900 F, because I've exploded large pots in my kiln at that
temperature. I had thought they were dry, but this actually happened on 2
separate occasions (apparently I'm a slow learner ).
Bonnie
Bonnie D. Hellman
Ouray, Colorado 81427
----- Original Message -----
From: "William & Susan Schran User"
To:
Sent: Tuesday, April 01, 2008 2:28 PM
Subject: Re: water and kiln
> On 4/1/08 1:56 PM, "Pfeiffer Fire Arts" wrote:
>
>> What did I do wrong? The kiln has a nice
>> small hole in the top that seemed the perfect place to do this but even
>> up
>> to 800F it still fogged the mirror. The ware seem to be quite dry.
>>
>
> Nothing wrong, that's chemically combined water, previous to that is water
> of absorption. And more than likely your thermocouple/pyrometer may not be
> that accurate.
>
>> The other question is are all electric kiln elements the same? We turned
>> ours up on high and the top and bottom elements were bright red but the
>> middle two were much dimmer. My first guess is the middle two have not
>> been
>> replaced but the outer two have been at some point in time.
> Depends what kiln you're firing.
> Some, such as L&L, use same elements top to bottom.
> Others, such as Skutt, use different elements at top & bottom than in the
> center, so the top & bottom may be glowing and the center ones will not.
>
> Bill
>
> --
> William "Bill" Schran
> wschran@cox.net
> wschran@nvcc.edu
> http://www.creativecreekartisans.com
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, change your
> subscription settings or unsubscribe/leave the list here:
> http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
Pottery by John on tue 1 apr 08
From: "Pfeiffer Fire Arts"
Subject: water and kiln
"The problem is the mirror never stopped fogging up! The kiln has a nice
small hole in the top that seemed the perfect place to do this but even up
to 800F it still fogged the mirror. "
Steve Slatin may be right about the moisture in the brick if the kiln has
been out of service for a while. I was given a kiln and my first firing of
it had a lot more moisture to evacuate than any firing since. Fortunately
you didn't explode anything and damage your ware or kiln.
Also, when I have bone dry ware and first fire up I leave the lid propped
open with the lower switch set to low and check after an hour (longer for
not so bone dry ware) to see if the mirror fogs. If it doesn't fog then the
lid is closed and I go into my normal firing schedule. The small hole you
describe may be the intake for a venting system...if there are one or
several small holes in the bottom also, then it was most likely a power
vented kiln. When I first power vented my kiln the instructions seemed to
indicate that the power vent would pull out that moisture, but I found the
propped lid greatly superior for the free water.
John Lowes
Sandy Springs GA
Ivor and Olive Lewis on wed 2 apr 08
Perhaps those who are concerned about the volume of water discharged =
when Kaolin decomposes and releases Hydroxyl Ions from its structure as =
free water should do some calculations.
Fact....One gram molecular weight of a substance when converted into a =
gas at standard temperature and pressure (15 deg Celsius and 760 mm =
Mercury) is 22.4 litres. .=20
Dividing by 4 1/2 gives Gallons. 22.4 litres =3D approx five gallons.
One Gram molecular mass of water has a mass of 18 grams. Two gram =
molecular masses of water are released from one gram molecular mass of =
Kaolin, 258 grams decomposes. So a kilogram of clay will evolve about 40 =
gallons of water vapour at NTP. This has to be adjusted because gas =
expands when it is heated by about 1/273 rd of its volume for every =
degree K(C) rise in temperature. Which takes us up to about 65 gallons =
of superheated steam. Which is a lot of gas that has to escape from a =
very small space .
If you have an open clay it might be of no consequence. If you have a =
tight porcelain or a fine grained earthenware it may lead to minor =
catastrophes during a bisque firing.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Snail Scott on wed 2 apr 08
On Apr 1, 2008, at 11:00 PM, Automatic digest processor wrote:
>
> Date: Tue, 1 Apr 2008 12:56:19 -0500
> From: Pfeiffer Fire Arts
>
> ...are all electric kiln elements the same? We turned
> ours up on high and the top and bottom elements were bright red but the
> middle two were much dimmer. My first guess is the middle two have not
> been
> replaced but the outer two have been at some point in time.
Sometimes yes, sometimes no. Many brands use hotter
elements top and bottom than they do in the middle,
to compensate for heat loss through the unelectrified
lid and floor. It's a good thing, since your firings will be
more even than they would be with matching elements.
-Snail
Pfeiffer Fire Arts on wed 2 apr 08
The kiln had been out of service for at least a few months and maybe years.
It is a cress b23h, looks to be 20 years old with a lot of hard use. I did
expect it to have some water in it from sitting around but I would think two
hours with the lid propped up on the second notch would have been more than
enough to dry it out. Had it set on low which meant it lowly went to ~300F.
No danger of a ware problem as we use a high grog clay that is very
forgiving.
We will load it up today and see how is does this time.
Thanks to all for the info.
Dan & Laurel in Elkmont Al
www.pfeifferFireArts.com
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Steve Slatin on thu 3 apr 08
It's be interesting to hear if you have the same effect the
second time you fired the kiln. -- Steve Slatin
Pfeiffer Fire Arts wrote:
The kiln had been out of service for at least a few months and maybe years.
It is a cress b23h, looks to be 20 years old with a lot of hard use. I did
expect it to have some water in it from sitting around but I would think two
hours with the lid propped up on the second notch would have been more than
enough to dry it out. Had it set on low which meant it lowly went to ~300F.
No danger of a ware problem as we use a high grog clay that is very
forgiving.
We will load it up today and see how is does this time.
Thanks to all for the info.
Steve Slatin --
Inanimate! Gooseberry paws two clause
inanimate! (overheard in Pittsburgh)
---------------------------------
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Ron Roy on fri 4 apr 08
Yes - water in the bricks - can take a day to get it out - I take as long
as it takes to get no steam coming out before I go over boiling.
Just fired 28 potrait heads - life sized - up to 2 inches thick - fired on
low for 3 days to make sure no moisture - none lost.
After the warm up I fired to cone 04 in 10 hours - thats about 100C per
hour - faster through the water smoking and quartz inversion. No grog in
the clay - smooth red earthenware.
RR
>We finally got an old small electric kiln up and running. Seems to work fine
>but having not fired an electric before I did end up with a few questions
>after reading a bit. One is I see lots of references to putting a mirror up
>to the top vent and not going up in temp before the mirror does not fog up.
>The problem is the mirror never stopped fogging up! After a few hours I went
>and did a somewhat fast bisque firing as it was getting very late to start a
>firing and all went very well. What did I do wrong? The kiln has a nice
>small hole in the top that seemed the perfect place to do this but even up
>to 800F it still fogged the mirror. The ware seem to be quite dry.
>
>The other question is are all electric kiln elements the same? We turned
>ours up on high and the top and bottom elements were bright red but the
>middle two were much dimmer. My first guess is the middle two have not been
>replaced but the outer two have been at some point in time.
>
>Thanks,
>
>
>Dan & Laurel in Elkmont Al
>www.pfeifferFireArts.com
>
>
>
>No virus found in this outgoing message.
>Checked by AVG.
>Version: 7.5.519 / Virus Database: 269.22.3/1354 - Release Date: 4/1/2008
>5:38 AM
>
>______________________________________________________________________________
>Clayart members may send postings to: clayart@lsv.ceramics.org
>
>You may look at the archives for the list, post messages, change your
>subscription settings or unsubscribe/leave the list here:
>http://www.acers.org/cic/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Pfeiffer Fire Arts on sun 6 apr 08
>>>It's be interesting to hear if you have the same effect the
second time you fired the kiln. -- Steve Slatin>>>
The short answer is yes it is much the same. My guess is we have not been
drying our ware to bone dry and by firing in a gas kiln all the time there
was not a way to tell. With our clay we never have a problem we could relate
to wet clay but I think we will include a day of two in a closet with a
heater going to see if we can improve the drying. I have done this in the
past to speed by the drying in wet weather and if that does not make any
difference I will give up trying.
I do like bisque firing in the kiln but need to find a larger one, this one
is very small and our work keeps getting bigger and we our getting a lot
faster.
Thanks to all.
Dan & Laurel in Elkmont Al
www.pfeifferFireArts.com
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11:12 AM
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