vince pitelka on sun 10 sep 00
> With a proper base test firing you do not need to watch your witness
cones.
> As a matter of fact watching your cones throught the peepholes has been
> proven to harm your eyes, not to mention the risk of burning yourself.
I have to disagree with this. If you want to guarantee accurate glaze
firings, you should include a witness cone in every firing. Each firing is
different in subtle ways, and the witness cone is the only way to insure
absolutely that you have reached the desired temperature.
When glaze-firing with a gas kiln we always use a multi-cone-pack, but
people are often complacent about using a witness cone in electric kilns.
If your kiln seems to fire consistently on the Kiln-sitter or controller, it
is very easy to disregard this practice. At the least, you should
periodically include several cone-packs spaced through the kiln, so that
when you unload the kiln you can get a sense of exactly what the firing
temperature really was. If you fire with a controller, this will also tell
you when your thermocouples are going bad. But if you are firing sensitive
glazes, which misbehave if underfired or overfired, the best practice is to
use a witness cone and be around when the kiln shuts off so that you can
verify that you have reached temperature.
And regarding watching witness cones, it is easy to spread misinformation.
Watching witness cones is a perfectly normal practice, and can be done very
safely. Get a set of green-tinted safety glasses, and do not lean in too
close to the spy-hole, and you have nothing to worry about.
Best wishes -
- Vince
Vince Pitelka
Home - vpitelka@dekalb.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
http://www.craftcenter.tntech.edu/
GSM_ENT on mon 11 sep 00
Hi Vince!
You are so correct, witness cones MUST be used in every firing.
I guess I was not clear enough. I did not mean to say not to use witness
cones but to use them without having to be looking at them. If you can
properly calibrate your kiln by know its DELTA then you do not have to look
into the kiln.
Someone else posted a comment to hang the witness cone from the edge of the
shelf instead of standing them-that is truly incorrect. The witness cones
are designed to be used standing, that is why they have an 8 degree
headstart. If you place then sideways the effect of gravity on then is
different and their behavior is also different.
It would be better to refer these questions to the ORTON Firing Institute.
Afterall their charter calls for the research and development of heat with
emphasis on ceramics and they are the cone manufacturers. Tim Frederich is a
good point of contact there.
Tony
----- Original Message -----
From: vince pitelka
To:
Sent: Sunday, September 10, 2000 6:05 PM
Subject: Using witness cones
> > With a proper base test firing you do not need to watch your witness
> cones.
> > As a matter of fact watching your cones throught the peepholes has been
> > proven to harm your eyes, not to mention the risk of burning yourself.
>
> I have to disagree with this. If you want to guarantee accurate glaze
> firings, you should include a witness cone in every firing. Each firing
is
> different in subtle ways, and the witness cone is the only way to insure
> absolutely that you have reached the desired temperature.
>
> When glaze-firing with a gas kiln we always use a multi-cone-pack, but
> people are often complacent about using a witness cone in electric kilns.
> If your kiln seems to fire consistently on the Kiln-sitter or controller,
it
> is very easy to disregard this practice. At the least, you should
> periodically include several cone-packs spaced through the kiln, so that
> when you unload the kiln you can get a sense of exactly what the firing
> temperature really was. If you fire with a controller, this will also
tell
> you when your thermocouples are going bad. But if you are firing
sensitive
> glazes, which misbehave if underfired or overfired, the best practice is
to
> use a witness cone and be around when the kiln shuts off so that you can
> verify that you have reached temperature.
>
> And regarding watching witness cones, it is easy to spread misinformation.
> Watching witness cones is a perfectly normal practice, and can be done
very
> safely. Get a set of green-tinted safety glasses, and do not lean in too
> close to the spy-hole, and you have nothing to worry about.
> Best wishes -
> - Vince
>
> Vince Pitelka
> Home - vpitelka@dekalb.net
> 615/597-5376
> Work - wpitelka@tntech.edu
> 615/597-6801 ext. 111, fax 615/597-6803
> Appalachian Center for Crafts
> Tennessee Technological University
> 1560 Craft Center Drive, Smithville TN 37166
> http://www.craftcenter.tntech.edu/
>
>
____________________________________________________________________________
__
> 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.
Martin Howard on tue 12 sep 00
I have stopped looking at the witness cones, during the firing cycle.
BUT, they are always there to tell me, on opening, just what cone was
reached.
That is in an electric kiln.
How else can you become aware that the elements are getting worn, or that
one has broken. Always have three at the top and three at the bottom.
Mine are 1,2 and 3 at the top and 01,1 and 2 at the bottom.
After singeing eyebrows once and realising that opening both peep holes
causes a draught onto the ware, I have stopped using the peep holes at all.
They remain closed during the whole cycle. Only the top flap is left open
until after 800 degrees on the way up, so that all water can escape.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
ASHPOTS@AOL.COM on tue 12 sep 00
hey all, i do use witness cones and i also make my cone packs as Lizards. As
the cones bend they look like fins .I bring cone packs to street shows and
have them sitting in my booth. Some people pick them up and it gives me a
oppertunity to discuss the cone packs and also clay and my work.
I mite have to start selling them, because people want to buy the lizard cone
packs.
PS I will be a Captain with the Chattanooga Ducks this week.
Captain Mark "Lookout Mountain Pottery"
GSM_ENT on tue 12 sep 00
Hi!
WP Dawson recommends wo wait until 1200 degrees F.
Tony
----- Original Message -----
From: Martin Howard
To:
Sent: Monday, September 11, 2000 11:56 PM
Subject: Re: Using witness cones
> I have stopped looking at the witness cones, during the firing cycle.
> BUT, they are always there to tell me, on opening, just what cone was
> reached.
> That is in an electric kiln.
>
> How else can you become aware that the elements are getting worn, or that
> one has broken. Always have three at the top and three at the bottom.
> Mine are 1,2 and 3 at the top and 01,1 and 2 at the bottom.
>
> After singeing eyebrows once and realising that opening both peep holes
> causes a draught onto the ware, I have stopped using the peep holes at
all.
> They remain closed during the whole cycle. Only the top flap is left open
> until after 800 degrees on the way up, so that all water can escape.
>
> Martin Howard
> Webb's Cottage Pottery
> Woolpits Road, Great Saling
> BRAINTREE, Essex CM7 5DZ
> England
> martin@webbscottage.co.uk
>
>
____________________________________________________________________________
__
> 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.
David Hewitt on wed 13 sep 00
In message , Martin Howard writes
>I have stopped looking at the witness cones, during the firing cycle.
>BUT, they are always there to tell me, on opening, just what cone was
>reached.
>That is in an electric kiln.
>
>How else can you become aware that the elements are getting worn, or that
>one has broken.
I have a kWh meter fitted to the kiln so that I can see the usage in
kWh. This of course increase as the kiln elements get older and worn and
also very quickly shows if an element has broken and, by turning off one
or more elements, which one has broken. I have never regretted the
initial cost of fitting the meter.
>Always have three at the top and three at the bottom.
>Mine are 1,2 and 3 at the top and 01,1 and 2 at the bottom.
>
>After singeing eyebrows once and realising that opening both peep holes
>causes a draught onto the ware, I have stopped using the peep holes at al=
>l.
>They remain closed during the whole cycle. Only the top flap is left open
>until after 800 degrees on the way up, so that all water can escape.
>
>Martin Howard
>Webb's Cottage Pottery
>Woolpits Road, Great Saling
>BRAINTREE, Essex CM7 5DZ
>England
>martin@webbscottage.co.uk
>
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Web site http://www.dhpot.demon.co.uk
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