Charles Gareri on tue 19 nov 96
I am firing to cone 5. I used to just break off a large cone to use in
the kiln sitter, when I ran out of Jr. cones. Did I recently hear
somebody say this is not a good idea? Also I can't remember if you used
a cone higher, if you used the large cones...
--
(. .)
-----------ooO-(_)-Ooo----------------------
" Ars longa; vita brevis"
(Art is long, life is short)-Hippocrates
Charlie Gareri E-mail cgareri@netride.com
Pike High School/Art Dept./Indianapolis Indiana USA
Frederich, Tim on thu 19 sep 02
Pat,
When you look at a product that has a cone reference number on it, they are
usually refering to the Orton Cone numbering system. Some European products
may refer to the Seger numbers. Orton is now usually used as the standard
around the world because they are universally available and their reputation
for tested accuracy (within + or - 2 degrees C). Please refer to any cone
chart published after 1996 for the correct end point temperatures at a
specific heating rate. Cone 6 fired at 60 degrees C/108 degrees F per hour
during the last part of the firing, will give you end point temperatures of
1222 degrees C/2232 degrees F.
I hope this answers your question. Please contact me if you have further
questions.
Best regards,
Tim Frederich, Orton Ceramic Foundation
Patty Potter on thu 19 sep 02
Dear Tim,
You interpreted my question correctly. Thanks a lot for your reply.
Pat
___________________
On Thu, 19 Sep 2002 11:00:09 -0400, Frederich, Tim
wrote:
>Pat,
>When you look at a product that has a cone reference number on it, they are
>usually refering to the Orton Cone numbering system. Some European
products
>may refer to the Seger numbers. Orton is now usually used as the standard
>around the world because they are universally available and their
reputation
>for tested accuracy (within + or - 2 degrees C). Please refer to any cone
>chart published after 1996 for the correct end point temperatures at a
>specific heating rate. Cone 6 fired at 60 degrees C/108 degrees F per hour
>during the last part of the firing, will give you end point temperatures of
>1222 degrees C/2232 degrees F.
>
>I hope this answers your question. Please contact me if you have further
>questions.
>
>Best regards,
>
>Tim Frederich, Orton Ceramic Foundation
>
>___________________________________________________________________________
___
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>
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>
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melpots@pclink.com.
Snail Scott on wed 13 oct 10
On Oct 13, 2010, at 1:00 PM, Sara Goldhawk wrote:
> ...I did not purchase any witness cones for the bisque firing,
> but feel I should use one...
I seldom bother. I judge by the clay's result whether
it's in the ballpark for the right cone or not. I find that
any discrepancies between sitters and witness cones,
or witness cones and pyrometers, are more evident
in a high temperature firing, and besides, I'm just not
very fussy about my bisque temperatures. (If I did
quantity production of catalog product lines, I'd care
more.) I keep low-fire witness cones on hand for
low-temperature glaze firings, not bisque, but I do
use them to check after I've just done major repairs.
> It seems that I should place one in the center for
> the kiln away from the kiln sitter and wall. Can I place one of the
> 06 cones in
> a lump of dry clay as a witness cone? I didn't think I could just
> place it on the
> shelf by itself. I did not buy a plaque for the cones...
You mean use a sitter cone as a witness cone?
No, this just doesn't work well at all. Use a proper
witness cone if you're going to use any. You
certainly don't need a pre-made cone plaque for
cones, though! That is what scrap clay is for. Just
make sure the base angle of the cone is correct;
that's the most important thing.
You can probably get away with using no witness
cones for a bisque, but it's not a bad idea to have
some, just to check now and then on the accuracy
of your sitter at those temperatures (if you care).
You still want to keep an eye on the firing, but if you
don't need pinpoint accuracy (and most folks don't,
for bisque), you can learn to read the color accurately
enough for most purposes. Still, witness cones are
the cheapest insurance going; why not spring for a
box in your bisque range, especially while you are
learning the behavior of this new (to you) kiln?
>
> I plan to make a test bisque fire this weekend...
Why not make it a high-temperature test firing? That
will be far more definitive in telling you what the offset
for the sitter needs to be, and whether this kiln can do
what you need from it. If it can hack that, bisque will
be no problem, but a bisque may not tell you everything
you want to know.
-Snail
Sara Goldhawk on wed 13 oct 10
I was given an old Crusader kiln (at least 40 years old) which hasn't bee=
=3D
n used=3D20
in 10 years. I've been at a community studio for 12 years and this is my=
=3D
first=3D20
time firing on my own (I did not do any firing previously). My kiln uses=
=3D
a kiln=3D20
sitter and is missing a cone support bar so I have a set on order as well=
=3D
as=3D20
some witness cones (self supporting) for the glaze firing and protective=3D=
20=3D
glasses. However, I did not purchase any witness cones for the bisque fi=
=3D
ring,=3D20
but feel I should use one. It seems that I should place one in the cente=
=3D
r for=3D20
the kiln away from the kiln sitter and wall. Can I place one of the 06 c=
=3D
ones in=3D20
a lump of dry clay as a witness cone? I didn't think I could just place i=
=3D
t on the=3D20
shelf by itself. I did not buy a plaque for the cones.
Fortunately I have the manuals for the kiln and kiln sitter, and I know t=
=3D
he=3D20
previous owner. I just want to take extra precautions because the kiln i=
=3D
s so=3D20
old and I plan to make a test bisque fire this weekend. Any advice for t=
=3D
his=3D20
situation would be helpful. Thanks.
William & Susan Schran User on wed 13 oct 10
On 10/13/10 2:00 PM, "Sara Goldhawk" wrote:
> My kiln uses a kiln
> sitter and is missing a cone support bar so I have a set on order as well=
as
> some witness cones (self supporting) for the glaze firing and protective
> glasses. However, I did not purchase any witness cones for the bisque fi=
ring,
> but feel I should use one. It seems that I should place one in the cente=
r for
> the kiln away from the kiln sitter and wall. Can I place one of the 06 c=
ones
> in a lump of dry clay as a witness cone? I didn't think I could just pla=
ce it
>on the shelf by itself. I did not buy a plaque for the cones.
Yes, you can press cones into plaques of clay, don't need much clay, but do
punch full of needle holes to help dry out well.
Though you can, it is not suggested using small cones as witness cones.
If you are glaze firing to ^6, then you will want ^5, ^6, ^7 in each firing=
.
For bisque, if you are firing to ^06, I have found ^06 & ^04 to be all I
need for witness cones.
I also recommend you do not fire by the kiln sitter, but by witness cones.
Think of the kiln sitter only as emergency backup in case you can't get to
the kiln when necessary. If the kiln sitter shuts kiln off before witness
cone has fallen, carefully lift the fallen bar, push in button to restart,
then slowly bring the bar back down and it won't shut down kiln.
I would suggest you first few bisque and glaze firings that you check the
progress and write in log every hour, this will give you a better idea how
long each firing takes and you can see when elements begin to wear out (whe=
n
firing gets slower). Be good idea to have pyrometer/thermocouple to more
easily track rate of heating ramp.
I used a Crusader kiln back in grad school (1970's), was a nice kiln.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
John Rodgers on wed 13 oct 10
Hi Sara,
I had an old Crusader - a big one - diameter. I did not have an
additional ring or collar on top. I had it, but never used it. Never
found a need for it. My Crusader was so old it didn't even have a kiln
sitter. It had 6 infinity switches with a range of to 10 with the "0"
being "Off" I had to manually set each switch, and when the firing was
done, I had to manually turn the kiln off. I used the free standing
witness cones placed on the shelf. I drilled through and inserted a
pyrometer probe on one side, and after a little experience with the
kiln, when the pyrometer showed being close to a chosen temperature, I
would begin to watch the cone on the shelf in front of the peep hole. As
the firing got ever closer to completion, the cone would slowly begin to
bend, I would just keep an eye on it until it was where I wanted it, and
I would shut the kiln off. By "keeping and eye on it" I don't mean I
just stared into that near white hot kiln while looking a that cone. I
would just pop the peep hole plug out - take a peep, then put it back
in. The closer I got to the finish, the more frequently I would look.
But I would not just stare into that heat and radiation. A flash light
would aid seeing the cone in the heat.
A very old ceramics lady in my area told me that I would get the best
firings ever with that Crusader if I would add one more thing ot the
procedure. I asked "What?" and she said fire it to maturity with the
bottom peephole out. I asked why - what does that do. She said " The
little bit of air fro the hole helps set currents in the kiln atmosphere
into motion, thereby more readily equalizing the temperatures in the
kiln, thus producing a better firing. Do that, and you will have some of
the best firings ever!"
Guess what. She was right. Of all my kilns I have had over the years,
that old Crusader gave me the best electric kiln oxidation firings I
have ever had.
Sadly, one day, I went to move the kiln and it just crumbled into
rubble. I salvaged the switches, the sheet metal, and some other parts,
thinking that I would rebuild it, but I probably won't. Most likely I
will simply build a complete new kiln. The new, fancy kilns, kilns with
automatic switches, kiln sitters, computers and all that - they are
great, but even so - there is a place for a simple, easy to operate,
manually switched, eyeballed, Cone 10 kiln.
Good luck.
John
John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com
On 10/13/2010 1:00 PM, Sara Goldhawk wrote:
> I was given an old Crusader kiln (at least 40 years old) which hasn't bee=
n used
> in 10 years. I've been at a community studio for 12 years and this is my=
first
> time firing on my own (I did not do any firing previously). My kiln uses=
a kiln
> sitter and is missing a cone support bar so I have a set on order as well=
as
> some witness cones (self supporting) for the glaze firing and protective
> glasses. However, I did not purchase any witness cones for the bisque fi=
ring,
> but feel I should use one. It seems that I should place one in the cente=
r for
> the kiln away from the kiln sitter and wall. Can I place one of the 06 c=
ones in
> a lump of dry clay as a witness cone? I didn't think I could just place i=
t on the
> shelf by itself. I did not buy a plaque for the cones.
>
> Fortunately I have the manuals for the kiln and kiln sitter, and I know t=
he
> previous owner. I just want to take extra precautions because the kiln i=
s so
> old and I plan to make a test bisque fire this weekend. Any advice for t=
his
> situation would be helpful. Thanks.
>
>
Sara Goldhawk on thu 14 oct 10
THANKS everyone for your very helpful responses. I've also just moved (t=
=3D
o=3D20
Rochester, NY) area so I'm getting used to where I can get supplies. I'v=
=3D
e=3D20
been driving to Syracuse (2 hours away), and ordered some of the cones fr=
=3D
om=3D20
Bailey Pottery further down state and not sure when they'll arrive in the=
=3D
mail.=3D20=3D20
Now I called a local pottery supplier and sure enough, they have what I n=
=3D
eed=3D20
so I'm going to pick up some bisque firing witness cones later today. Be=
=3D
tter=3D20
safe than sorry. I'm sure I'll write again with more questions!!
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