Jennifer Jeglinski on wed 16 feb 11
I recently fired my mid range clay to what I thought was cone 6. I have the=
=3D
program run until 2232 degrees and hold it for 10 minutes to ensure all th=
=3D
e glazes fully mature. I normally use a cone 6 self support cone to make su=
=3D
re it reached temperature. This last firing I bought cones 7 and 8 to see j=
=3D
ust how hot it was firing and cone 8 melted flat! My kiln is not supposed t=
=3D
o fire hotter than cone 8=3D2C so I=3D92m wondering does holding it for 10 =
minu=3D
tes create more heat to bring it up to the next cone? All this time I reall=
=3D
y thought I was firing to cone 6 and wasn=3D92t.
Overall the colors were a bit more washed out than normal=3D2C my guess is =
be=3D
cause it got hotter. I=3D92ve fired about 20 kilns (both bisque and glaze) =
wi=3D
th the elements that are there and it was only fired a handful of times whe=
=3D
n I got it. The elements appear to be in good shape. Is it possible my ther=
=3D
mocouple needs replacing?=3D20
Thanks in advance for any advise you can provide!
Jen
=3D
gwynneth rixon on thu 17 feb 11
The cones don't just measure temperature, they measure heat work.
Gwynneth
Wales
www.gwynnethrixonceramics.co.uk
On Thu, Feb 17, 2011 at 4:04 AM, Jennifer Jeglinski <
jenjeglinski4@hotmail.com> wrote:
> I recently fired my mid range clay to what I thought was cone 6. I have t=
=3D
he
> program run until 2232 degrees and hold it for 10 minutes to ensure all t=
=3D
he
> glazes fully mature. I normally use a cone 6 self support cone to make su=
=3D
re
> it reached temperature. This last firing I bought cones 7 and 8 to see ju=
=3D
st
> how hot it was firing and cone 8 melted flat! My kiln is not supposed to
> fire hotter than cone 8, so I=3D92m wondering does holding it for 10 minu=
te=3D
s
> create more heat to bring it up to the next cone? All this time I really
> thought I was firing to cone 6 and wasn=3D92t.
>
> Overall the colors were a bit more washed out than normal, my guess is
> because it got hotter. I=3D92ve fired about 20 kilns (both bisque and gla=
ze=3D
)
> with the elements that are there and it was only fired a handful of times
> when I got it. The elements appear to be in good shape. Is it possible my
> thermocouple needs replacing?
>
> Thanks in advance for any advise you can provide!
>
> Jen
>
>
John Rodgers on thu 17 feb 11
Jenifer,
You can achieve the next hotter cone by holding for a time at the next
lower cone. That is, for example, holding at cone 5 for a time, will
give you the heat work of cone 6 - sort of like cooking a turkey at
lower heat to ensure it gets cooked through and through.
Here's a quote from my Paragon Manual:
Example: to fire to cone 05, program for cone 06 and add 45-60 minutes
of hold time. (this principle applies to the higher cones 1 thru 10 as
well) BTW - that time shown here is not set in stone.
Place three witness or shelf cones 5, 6 and 7 at peephole level about
10-12 inches from the peephole. Arrange them in order from left to
right. Program in your firing and hold time, Fire the kiln, and as the
kiln heats to temperature of the first cone, begin to watch the cones
through the peephole (with good eye protection of course). When the
appropriate cone bends to the proper position - three o'clock or tip
down - quickly note the temp and the time to get from one cone to the
next, then hit Stop. Now you have a reference point for your firings in
the future, regardless of what the computer says is the correct cone
fire setting.
If you temperatures are off, and don't match up with the cones bending,
most computerized kilns allow you to make adjustments to bring the two
in line with each other.
But again, you can get to the next hotter cone by holding programming a
hold. Like hold on cone 5 long enough and the heat work over time will
get you to cone 6. But you MUST work with your cones on the shelf to
achieve this, even with a computerized kiln, until you have the
specifics of your kiln worked out. Always make copious notes on each
firing. Not only will that help in getting high quality pottery from
your firing, it will help when it comes time to make repairs or
troubleshoot your kiln.
John
John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com
On 2/16/2011 10:04 PM, Jennifer Jeglinski wrote:
> I recently fired my mid range clay to what I thought was cone 6. I have t=
he program run until 2232 degrees and hold it for 10 minutes to ensure all =
the glazes fully mature. I normally use a cone 6 self support cone to make =
sure it reached temperature. This last firing I bought cones 7 and 8 to see=
just how hot it was firing and cone 8 melted flat! My kiln is not supposed=
to fire hotter than cone 8, so I=92m wondering does holding it for 10 minu=
tes create more heat to bring it up to the next cone? All this time I reall=
y thought I was firing to cone 6 and wasn=92t.
>
> Overall the colors were a bit more washed out than normal, my guess is be=
cause it got hotter. I=92ve fired about 20 kilns (both bisque and glaze) wi=
th the elements that are there and it was only fired a handful of times whe=
n I got it. The elements appear to be in good shape. Is it possible my ther=
mocouple needs replacing?
>
> Thanks in advance for any advise you can provide!
>
> Jen
>
>
>
Taylor Hendrix on thu 17 feb 11
Yes Jennifer, it is possible your thermocouple needs replacing. Check
connections and visually inspect thermocouple probe if you can. Could
be just some burned or shorting wires. Don't try to repair t/c wires.
If you can afford it, buy a new one and check next firing with cones.
Be sure to replace with the correct type of thermocouple and might as
well check to see if you have programmed any tc offset or cone offsets
in your controller.
Taylor, in Rockport TX
wirerabbit1 on Skype (-0600 UTC)
http://wirerabbit.blogspot.com
http://wirerabbitpots.blogspot.com
http://www.flickr.com/photos/wirerabbit/
On Wed, Feb 16, 2011 at 10:04 PM, Jennifer Jeglinski
wrote:
> I recently fired my mid range clay to what I thought was cone 6. I have t=
=3D
he program run until 2232 degrees and hold it for 10 minutes to ensure all =
=3D
the glazes fully mature. I normally use a cone 6 self support cone to make =
=3D
sure it reached temperature. This last firing I bought cones 7 and 8 to see=
=3D
just how hot it was firing and cone 8 melted flat! My kiln is not supposed=
=3D
to fire hotter than cone 8, so I=3DE2=3D80=3D99m wondering does holding it=
for 1=3D
0 minutes create more heat to bring it up to the next cone? All this time I=
=3D
really thought I was firing to cone 6 and wasn=3DE2=3D80=3D99t.
>
> Overall the colors were a bit more washed out than normal, my guess is be=
=3D
cause it got hotter. I=3DE2=3D80=3D99ve fired about 20 kilns (both bisque a=
nd gla=3D
ze) with the elements that are there and it was only fired a handful of tim=
=3D
es when I got it. The elements appear to be in good shape. Is it possible m=
=3D
y thermocouple needs replacing?
>
> Thanks in advance for any advise you can provide!
>
> Jen
>
>
Lynn Goodman Porcelain Pottery on thu 17 feb 11
Hi Jennifer,
Yes, your thermocouples may be bad, and there may also be a problem =3D20
with the motherboard. You should not, however, be trusting them, even =3D20=
=3D
if they were working perfectly. This is a melt-down waiting to happen.
You should ALWAYS be present when your kiln is due to reach =3D20
temperature. If you have witness cones where they are visible in the =3D20
peepholes, you can turn off the kiln if they drop before the kiln =3D20
program is done, so your kiln doesn't over fire. You can only do this =3D20=
=3D
if you are present at the end of the firing.
You can fine-tune the program to run cooler or hotter (look at the =3D20
manual for directions on how to do this). If you replace the =3D20
thermocouples you will have to test everything again, because all =3D20
thermocouples read the temperature a little differently.
You can also just work within the problems that you know about (by =3D20
setting the program to turn off the kiln two cones "early"), since =3D20
they seem to be stable and not changing.
Hope this helps
Lynn
On Feb 16, 2011, at 11:04 PM, Jennifer Jeglinski wrote:
> I recently fired my mid range clay to what I thought was cone 6. I =3D20
> have the program run until 2232 degrees and hold it for 10 minutes =3D20
> to ensure all the glazes fully mature. I normally use a cone 6 self =3D20=
=3D
> support cone to make sure it reached temperature. This last firing I =3D2=
0=3D
> bought cones 7 and 8 to see just how hot it was firing and cone 8 =3D20
> melted flat! My kiln is not supposed to fire hotter than cone 8, so =3D20=
=3D
> I=3D92m wondering does holding it for 10 minutes create more heat to =3D2=
0
> bring it up to the next cone? All this time I really thought I was =3D20
> firing to cone 6 and wasn=3D92t.
>
Lynn Goodman Porcelain
Cell 347-526-9805
www.lynngoodmanporcelain.com
Jennifer Jeglinski on thu 17 feb 11
Thanks everyone for the advise! I'm guessing I was firing hotter than I tho=
=3D
ught all along. It seems as though my Cone 7 self supports were always bent=
=3D
down=3D2C but not melted into a puddle like it was this last time.=3D20
=3D20
Without repairing my thermocouple or motherboard (yikes!!)=3D2C is there a =
wa=3D
y I can work with my current set up and witness cones? I would be very surp=
=3D
rised if the thermocouple was broken as the kiln has been fired in total le=
=3D
ss than 30 times over the years. Can you tell by just looking at it?
=3D20
Clearly=3D2C I probably won't need the 10 minute soak at the end. I origina=
ll=3D
y did that to make sure the glazes hit temp and melted nicely. Should I sti=
=3D
ll set the target temp at 2232 (for Cone 6/7) knowing that it fires hotter =
=3D
than I think?=3D20
=3D20
Jen
jjceramics
=3D20
> Date: Wed=3D2C 16 Feb 2011 23:04:10 -0500
> From: jenjeglinski4@HOTMAIL.COM
> Subject: Cone 6 electric kiln mishap
> To: Clayart@LSV.CERAMICS.ORG
>=3D20
> I recently fired my mid range clay to what I thought was cone 6. I have t=
=3D
he program run until 2232 degrees and hold it for 10 minutes to ensure all =
=3D
the glazes fully mature. I normally use a cone 6 self support cone to make =
=3D
sure it reached temperature. This last firing I bought cones 7 and 8 to see=
=3D
just how hot it was firing and cone 8 melted flat! My kiln is not supposed=
=3D
to fire hotter than cone 8=3D2C so I=3D92m wondering does holding it for 1=
0 mi=3D
nutes create more heat to bring it up to the next cone? All this time I rea=
=3D
lly thought I was firing to cone 6 and wasn=3D92t.
>=3D20
> Overall the colors were a bit more washed out than normal=3D2C my guess i=
s =3D
because it got hotter. I=3D92ve fired about 20 kilns (both bisque and glaze=
) =3D
with the elements that are there and it was only fired a handful of times w=
=3D
hen I got it. The elements appear to be in good shape. Is it possible my th=
=3D
ermocouple needs replacing?=3D20
>=3D20
> Thanks in advance for any advise you can provide!
>=3D20
> Jen
>=3D20
>=3D20
=3D
William & Susan Schran User on thu 17 feb 11
On 2/17/11 2:21 PM, "Jennifer Jeglinski" wrote:
> Thanks everyone for the advise! I'm guessing I was firing hotter than I
> thought all along. It seems as though my Cone 7 self supports were always=
bent
> down, but not melted into a puddle like it was this last time.
>
> Without repairing my thermocouple or motherboard (yikes!!), is there a wa=
y I
> can work with my current set up and witness cones? I would be very surpri=
sed
> if the thermocouple was broken as the kiln has been fired in total less t=
han
> 30 times over the years. Can you tell by just looking at it?
>
> Clearly, I probably won't need the 10 minute soak at the end. I originall=
y did
> that to make sure the glazes hit temp and melted nicely. Should I still s=
et
> the target temp at 2232 (for Cone 6/7) knowing that it fires hotter than =
I
> think?
For this you'll need to position cones in front of spy hole and where
appropriate eye protection. Make sure there is a clear path behind cone to
an element so you can see it better.
Set your firing as before to 2232, then when kiln reaches about 2175, begin
watching the cones every 5 minutes. When you see ^6 go over, enter a "skip
step" into your controller (look in kiln manual).
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Arnold Howard on thu 17 feb 11
On 2/17/2011 1:21 PM, Jennifer Jeglinski wrote:
> Without repairing my thermocouple or motherboard (yikes!!), is there a wa=
y I can work with my current set up and witness cones? I would be very surp=
rised if the thermocouple was broken as the kiln has been fired in total le=
ss than 30 times over the years. Can you tell by just looking at it?
>
> Clearly, I probably won't need the 10 minute soak at the end. I originall=
y did that to make sure the glazes hit temp and melted nicely. Should I sti=
ll set the target temp at 2232 (for Cone 6/7) knowing that it fires hotter =
than I think?
Jen, it is unusual for a thermocouple to be two cones off. Your kiln
will fire too hot if the thermocouple has been pushed too far into the
firebrick wall. That can happen if a shelf bumps into the thermocouple.
Your kiln manual should include the correct distance the thermocouple
should extend into the firing chamber.
If the thermocouple were broken, you would get an error message instead
of a temperature readout.
Is the temperature readout steady, or does it fluctuate?
Does the temperature jump when you wiggle the thermocouple tip while the
kiln is idle?
You can compensate for an inaccurate thermocouple by firing to a
different cone in Cone-Fire, firing to a different temperature in
Ramp-Hold, or adjusting the Thermocouple Offset.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
John Rodgers on thu 17 feb 11
Jennifer,
Never ever depend solely on your computer to control your temp and kiln
shutoff.
I said it before. Put cones on a shelf 10 inches in front of a peep
hole, set your temperature for the firing, and hit the "Go" button. When
the temperature read out begins to get close to the desired temp - begin
watching those cones. Forget the computer at this point - Watch those
cones. When the appropriate cone bends - turn of the kiln. Firing complete.
If you are trying to get in a heat soak period - you still must watch
those cones. There is no other way to get this just exactly right,
computers not withstanding.
The best firings I have ever had - ever - were in an old Crusader kiln
that was fully manual. No computer, no kiln sitter. Just 6 infinity
switches. Each switch controlled a double ring of elements. Using a
pyrometer as a guide - and only as a guide - and really paying attention
to the cones sitting on the shelf - I got the best firings I have ever had.
Cones and time are the only way to go.
Good luck.
John
On 2/17/2011 1:21 PM, Jennifer Jeglinski wrote:
> I still set the target temp at 2232 (for Cone 6/7) knowing that it fires =
hotter than I think?
John Hesselberth on thu 17 feb 11
Hi Jen,
Move your target down to the point that your cone 6 is just tip touching =
=3D
at the end of your soak if you want to fire to cone 6. Thermocouples are =
=3D
not very accurate above 2000--at least not the ones supplied with most =3D
kilns. For example I set my end point temperature at 2190 with a 15 =3D
minute soak to hit cone 6. That is perfect for my kiln and my =3D
thermocouple. You will have to find out what is perfect for you, but it =3D
is not 2232
Cones are the gold standard. Trust them, not your thermocouple.
Regards,
John
www.masteringglazes.com
www.frogpondpottery.com
On Feb 17, 2011, at 2:21 PM, Jennifer Jeglinski wrote:
> Clearly, I probably won't need the 10 minute soak at the end. I =3D
originally did that to make sure the glazes hit temp and melted nicely. =3D
Should I still set the target temp at 2232 (for Cone 6/7) knowing that =3D
it fires hotter than I think?=3D20
>=3D20
> Jen
> jjceramics
Glistering Phaeton on thu 17 feb 11
Dear Jen,
I have two thoughts to pass along. The first is that if you want to do =3D
a
hold for your glazes to "mature," set the final temperature lower than =3D
your
original and program in a hold time at that lower temp. Then, as =3D
mentioned,
watch for the cone to go over.
The second thought relates to figuring out how to know when your firing =3D
is
scheduled to be over (so you know when to start checking the cones). =3D
Your
kiln may not tell you how long the total firing time is expected to be, =3D
so
you can calculate it using the ramp/hold method.
For example, my Paragon electric has the following schedule for ^5 =3D
medium
speed:
Step 1. 324=3DBA/hr to 1022=3DBA
Step 2. 153=3DBA/hr to 1122=3DBA
Step 3. 180=3DBA/hr to 1951=3DBA
Step 4. 108=3DBA/hr to 2167=3DBA
To figure how long it is going to take for this firing example to =3D
finish,
you'll need to do the following calculations, assuming your kiln starts =3D
at
72=3DBA:
1022=3DBA - 72=3DBA =3D3D 950=3DBA temp climb in Step 1.
950/324 =3D3D 2.93 hours (that's the total climb in Step 1 divided by the =
=3D
ramp
rate/hour)
1122=3DBA - 1022=3DBA =3D3D 100=3DBA temp climb in Step 2.
100/153 =3D3D .65 hours (total climb in Step 2 divided by the ramp =3D
rate/hour)
1951=3DBA - 1122=3DBA =3D3D 829=3DBA temp climb in Step 3.
829/180 =3D3D 4.6 hours (total climb in Step 3 divided by the ramp =3D
rate/hour)
2167=3DBA - 1951=3DBA =3D3D 216=3DBA temp climb in Step 4.
216/108 =3D3D 2 hours (total climb in Step 4 divided by the ramp =3D
rate/hour)
So the approximate time for this firing is:
2.92 + .65 + 4.6 + 2 =3D3D 10.17 hours, which in hours:minutes is ~10:10 =
=3D
(that's
60*.17 to convert decimal to minutes).
In this scenario, I would start looking at the cones somewhere around =3D
9:45
and make a note of the temperature when the cone bends to see if the
computer matches the reality.
Hope this helps,
=3D97Adam
in sunny Los Angeles
-----Original Message-----
From: Clayart [mailto:Clayart@LSV.CERAMICS.ORG] On Behalf Of Jennifer
Jeglinski
Sent: Thursday, February 17, 2011 11:22 AM
To: Clayart@LSV.CERAMICS.ORG
Subject: Re: Cone 6 electric kiln mishap
Thanks everyone for the advise! I'm guessing I was firing hotter than I
thought all along. It seems as though my Cone 7 self supports were =3D
always
bent down, but not melted into a puddle like it was this last time.=3D20
=3D20
Without repairing my thermocouple or motherboard (yikes!!), is there a =3D
way I
can work with my current set up and witness cones? I would be very =3D
surprised
if the thermocouple was broken as the kiln has been fired in total less =3D
than
30 times over the years. Can you tell by just looking at it?
=3D20
Clearly, I probably won't need the 10 minute soak at the end. I =3D
originally
did that to make sure the glazes hit temp and melted nicely. Should I =3D
still
set the target temp at 2232 (for Cone 6/7) knowing that it fires hotter =3D
than
I think?=3D20
=3D20
Jen
jjceramics
=3D20
> Date: Wed, 16 Feb 2011 23:04:10 -0500
> From: jenjeglinski4@HOTMAIL.COM
> Subject: Cone 6 electric kiln mishap
> To: Clayart@LSV.CERAMICS.ORG
>=3D20
> I recently fired my mid range clay to what I thought was cone 6. I =3D
have
the program run until 2232 degrees and hold it for 10 minutes to ensure =3D
all
the glazes fully mature. I normally use a cone 6 self support cone to =3D
make
sure it reached temperature. This last firing I bought cones 7 and 8 to =3D
see
just how hot it was firing and cone 8 melted flat! My kiln is not =3D
supposed
to fire hotter than cone 8, so I=3D92m wondering does holding it for 10 =3D
minutes
create more heat to bring it up to the next cone? All this time I really
thought I was firing to cone 6 and wasn=3D92t.
Steve Mills on thu 17 feb 11
Dear Jen,
you can work very successfully with the kit that you have got as it is,
provided you recognize that your thermocouple/pyrometer is basically
inaccurate.
No need to mend or change anything!
Set the programme as you have been doing, but rely entirely on witness cone=
=3D
s
(this is assuming you have a spy hole you can see them through!).
As has been said before, witness cones are the most reliable way of firing
any kiln. This is because they measure accumulated heat-work, not
temperature.
Thermocouples and pyrometers can only tell you the pure temperature current
at the time you look at the display, moreover as they get older they become
progressively inaccurate. This is nothing to do with the number of firings
that they experience, but is entirely time related.
The element in a thermocouple is composed of two dissimilar metals, and whe=
=3D
n
the joint between those two metals is heated, it creates a very small
electric current, which is measured by the pyrometer and converted into a
temperature reading.
The trouble is that over time the element degrades as the two dissimilar
metals react with each other and the amount of electrical charge generated
changes. No one has yet built a pyrometer that can measure and adjust to
this changing signal.
Industrially, thermocouple elements (usually type R or type S) are replaced
very frequently, something we tend not to do, because most people reckon
(wrongly) that if the meter is indicating, it's working, so why bother!
As an afterthought, I have observed that a lot of kilns are supplied in
America with type K. thermocouples. This is because they are cheap and
fairly hardy. The problem is that type K. have an accuracy limit at best o=
=3D
f
1200=3DB0C (2192 Fahrenheit), above that they become progressively inaccura=
te=3D
,
and that is from new!
Steve M
On 17 February 2011 19:21, Jennifer Jeglinski wr=
=3D
ote:
> Thanks everyone for the advise! I'm guessing I was firing hotter than I
> thought all along. It seems as though my Cone 7 self supports were always
> bent down, but not melted into a puddle like it was this last time.
>
> Without repairing my thermocouple or motherboard (yikes!!), is there a wa=
=3D
y
> I can work with my current set up and witness cones? I would be very
> surprised if the thermocouple was broken as the kiln has been fired in to=
=3D
tal
> less than 30 times over the years. Can you tell by just looking at it?
>
> Clearly, I probably won't need the 10 minute soak at the end. I originall=
=3D
y
> did that to make sure the glazes hit temp and melted nicely. Should I sti=
=3D
ll
> set the target temp at 2232 (for Cone 6/7) knowing that it fires hotter t=
=3D
han
> I think?
>
> Jen
> jjceramics
>
>
>
>
> > Date: Wed, 16 Feb 2011 23:04:10 -0500
> > From: jenjeglinski4@HOTMAIL.COM
> > Subject: Cone 6 electric kiln mishap
> > To: Clayart@LSV.CERAMICS.ORG
> >
> > I recently fired my mid range clay to what I thought was cone 6. I have
> the program run until 2232 degrees and hold it for 10 minutes to ensure a=
=3D
ll
> the glazes fully mature. I normally use a cone 6 self support cone to mak=
=3D
e
> sure it reached temperature. This last firing I bought cones 7 and 8 to s=
=3D
ee
> just how hot it was firing and cone 8 melted flat! My kiln is not suppose=
=3D
d
> to fire hotter than cone 8, so I=3D92m wondering does holding it for 10 m=
in=3D
utes
> create more heat to bring it up to the next cone? All this time I really
> thought I was firing to cone 6 and wasn=3D92t.
> >
> > Overall the colors were a bit more washed out than normal, my guess is
> because it got hotter. I=3D92ve fired about 20 kilns (both bisque and gla=
ze=3D
)
> with the elements that are there and it was only fired a handful of times
> when I got it. The elements appear to be in good shape. Is it possible my
> thermocouple needs replacing?
> >
> > Thanks in advance for any advise you can provide!
> >
> > Jen
> >
> >
>
>
Eric Hansen on thu 17 feb 11
The temperature "2232" is a number designated by Orton only for the
intention to select cones. I see it on the chart in front of me and
quote "Depending on the firing conditions the temperature may be only
a relative guide for the user" so - someone - somewhere - decided that
"2232" meant something other than what the literature clearly states.
I have seen people fire kilns this way, just turn it "on" with a
target "temperature" dialed in. This for certain will get different
results every time. I don't know that it is a recommended method of
firing by kiln manufacturers, if so - we need to decide what their
punishment should be for disseminating false information. Any
thoughts, Arnold??
SO - "2232" f. is the target temperature for a kiln increasing 270
degrees f. per hour to achieve cone 6. NOW!!! - cone 10 - at that at
of increase is less than one hour (270) difference (hmmm) and I
seriously doubt that your kiln will shoot past cone 10 if left on for
an extra hour, so I am thinking that the number given for a 270 degree
per hour climb is not relevant. I am willing to bet that "2194" f -
the number given for an increase of 108 degrees per hour - which is
also called "equal" to cone 6 in Orton's literature, might be closer
to cone 6 in the kiln. Maybe. In your situation I would try the 2194
number and see what happens to the witness cones. Before panic sets in
and money is spent trying to fix something that is not broken.
- h a n s e n -
p.s. I tried to search for the published resource quoted by it doesn't
seem to be online.
On Thu, Feb 17, 2011 at 2:21 PM, Jennifer Jeglinski
wrote:
> Thanks everyone for the advise! I'm guessing I was firing hotter than I t=
=3D
hought all along. It seems as though my Cone 7 self supports were always be=
=3D
nt down, but not melted into a puddle like it was this last time.
>
> Without repairing my thermocouple or motherboard (yikes!!), is there a wa=
=3D
y I can work with my current set up and witness cones? I would be very surp=
=3D
rised if the thermocouple was broken as the kiln has been fired in total le=
=3D
ss than 30 times over the years. Can you tell by just looking at it?
>
> Clearly, I probably won't need the 10 minute soak at the end. I originall=
=3D
y did that to make sure the glazes hit temp and melted nicely. Should I sti=
=3D
ll set the target temp at 2232 (for Cone 6/7) knowing that it fires hotter =
=3D
than I think?
>
> Jen
> jjceramics
>
>
>
>
>> Date: Wed, 16 Feb 2011 23:04:10 -0500
>> From: jenjeglinski4@HOTMAIL.COM
>> Subject: Cone 6 electric kiln mishap
>> To: Clayart@LSV.CERAMICS.ORG
>>
>> I recently fired my mid range clay to what I thought was cone 6. I have =
=3D
the program run until 2232 degrees and hold it for 10 minutes to ensure all=
=3D
the glazes fully mature. I normally use a cone 6 self support cone to make=
=3D
sure it reached temperature. This last firing I bought cones 7 and 8 to se=
=3D
e just how hot it was firing and cone 8 melted flat! My kiln is not suppose=
=3D
d to fire hotter than cone 8, so I=3D92m wondering does holding it for 10 m=
in=3D
utes create more heat to bring it up to the next cone? All this time I real=
=3D
ly thought I was firing to cone 6 and wasn=3D92t.
>>
>> Overall the colors were a bit more washed out than normal, my guess is b=
=3D
ecause it got hotter. I=3D92ve fired about 20 kilns (both bisque and glaze)=
w=3D
ith the elements that are there and it was only fired a handful of times wh=
=3D
en I got it. The elements appear to be in good shape. Is it possible my the=
=3D
rmocouple needs replacing?
>>
>> Thanks in advance for any advise you can provide!
>>
>> Jen
>>
>>
>
--=3D20
Eric Alan Hansen
Stonehouse Studio Pottery
Alexandria, Virginia
americanpotter.blogspot.com
thesuddenschool.blogspot.com
hansencookbook.blogspot.com
"Simplify, simplify, simplify" - Thoreau
Arnold Howard on thu 17 feb 11
On 2/17/2011 4:14 PM, Glistering Phaeton wrote:
> In this scenario, I would start looking at the cones somewhere around 9:4=
5
> and make a note of the temperature when the cone bends to see if the
> computer matches the reality.
Here is a chart of firing times for Orton's Sentry controller Cone-Fire
mode:
http://www.paragonweb.com/files/manuals/speed%20chart_ConeFire.pdf
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
John Post on thu 17 feb 11
I have 5 different electric kilns that I fire. 3 in my studio, two in =3D2=
0=3D
the schools I teach at.
To reach cone 6 in the larger electric kilns I need to program the =3D20
kiln to hit 2200=3DB0 Fahrenheit.
On my smaller electric kilns I program them to hit 2170=3DB0 Fahrenheit.
These profiles each yield a perfect cone 6 firing in their respective =3D20=
=3D
kilns. The only way I figured out how to get the same results in every =3D2=
0=3D
kiln was to put cone several cone packs in each kiln every time I fire =3D2=
0=3D
it.
John Post
Sterling Heights, Michigan
http://www.johnpost.us
Follow me on Twitter
https://twitter.com/UCSArtTeacher
On Feb 17, 2011, at 2:21 PM, Jennifer Jeglinski wrote:
> Thanks everyone for the advise! I'm guessing I was firing hotter =3D20
> than I thought all along. It seems as though my Cone 7 self supports =3D2=
0=3D
> were always bent down, but not melted into a puddle like it was this =3D2=
0=3D
> last time.
>
> Without repairing my thermocouple or motherboard (yikes!!), is there =3D2=
0=3D
> a way I can work with my current set up and witness cones? I would =3D20
> be very surprised if the thermocouple was broken as the kiln has =3D20
> been fired in total less than 30 times over the years. Can you tell =3D20=
=3D
> by just looking at it?
>
> Clearly, I probably won't need the 10 minute soak at the end. I =3D20
> originally did that to make sure the glazes hit temp and melted =3D20
> nicely. Should I still set the target temp at 2232 (for Cone 6/7) =3D20
> knowing that it fires hotter than I think?
>
> Jen
> jjceramics
>
>
>
>
>> Date: Wed, 16 Feb 2011 23:04:10 -0500
>> From: jenjeglinski4@HOTMAIL.COM
>> Subject: Cone 6 electric kiln mishap
>> To: Clayart@LSV.CERAMICS.ORG
>>
>> I recently fired my mid range clay to what I thought was cone 6. I =3D20=
=3D
>> have the program run until 2232 degrees and hold it for 10 minutes =3D20=
=3D
>> to ensure all the glazes fully mature. I normally use a cone 6 self =3D2=
0=3D
>> support cone to make sure it reached temperature. This last firing =3D20=
=3D
>> I bought cones 7 and 8 to see just how hot it was firing and cone 8 =3D2=
0=3D
>> melted flat! My kiln is not supposed to fire hotter than cone 8, so =3D2=
0=3D
>> I=3D92m wondering does holding it for 10 minutes create more heat to =3D=
20=3D
>> bring it up to the next cone? All this time I really thought I was =3D20=
=3D
>> firing to cone 6 and wasn=3D92t.
>>
>> Overall the colors were a bit more washed out than normal, my guess =3D2=
0=3D
>> is because it got hotter. I=3D92ve fired about 20 kilns (both bisque =3D=
20=3D
>> and glaze) with the elements that are there and it was only fired a =3D2=
0=3D
>> handful of times when I got it. The elements appear to be in good =3D20
>> shape. Is it possible my thermocouple needs replacing?
>>
>> Thanks in advance for any advise you can provide!
>>
>> Jen
>>
>>
Jim Willett on fri 18 feb 11
Jennifer, it is time and temperature. Here is a good chart to give you a =
=3D
better=3D20
idea.
http://www.bigceramicstore.com/information/ConeChart.html=3D20
There are as many "experts" out there as there are potters firing kilns. =
=3D
Find what=3D20
works for you and stick with it.=3D20
For example we have fired computer controlled kilns for 20 years to a tim=
=3D
e and=3D20
temperature ramp setting, without cones. At one time four kilns, two 16's=
=3D
a ten=3D20
and a 7 cu ft. No "meltdowns". Cone Art kilns. A glaze load out of one k=
=3D
iln would=3D20
match a glaze load from another and from last year and the year before, a=
=3D
nd so=3D20
on. If you are getting the results you want then you are doing it right. =
=3D
End of=3D20
story.
Jim Willett and Cindy Clarke
Out of the Fire Studio
Edmonton, Alberta
http://www.outofthefirestudio.com
Snail Scott on fri 18 feb 11
On Feb 16, 2011, at 10:04 PM, Jennifer Jeglinski wrote:
> I recently fired my mid range clay to what I thought was cone 6. I =3D
have the program run until 2232 degrees and hold it for 10 minutes to =3D
ensure all the glazes fully mature...cone 8 melted flat! My kiln is not =3D
supposed to fire hotter than cone 8, so I=3D92m wondering does holding it =
=3D
for 10 minutes create more heat to bring it up to the next cone? All =3D
this time I really thought I was firing to cone 6 and wasn=3D92t...
> Is it possible my thermocouple needs replacing?=3D20
It wasn't the ten minute hold that did it.
You are probably right that you were firing to ^8 all along.
Here's the question: If your stuff looked great and functioned=3D20
properly (well-melted glazes, vitrified clay, no warping or=3D20
bloating), then why change it? Just re-label everything to=3D20
the actual cone you were using - apparently ^8. If it was=3D20
working for you, don't change it unless there's a reason.
One reason to change might be that ^8 puts a lot more wear=3D20
and tear on electric elements than ^6, because the thin=3D20
insulation of electric kilns means you lose more heat=3D20
through the brick the longer you fire. That's the main reason=3D20
some electric kilns are rated for lower cones, like ^6 or ^8.=3D20
It's not that the elements can't crank the heat; it's that the=3D20
efficiency drops like a rock because at a certain point you=3D20
are losing heat almost as fast as you put it in.=3D20
So, going back to a true ^6 might save a fair amount of cash,=3D20
but if you have to reformulate your glazes and your clay is=3D20
undervitrified at that cone, then you aren't really coming out=3D20
ahead.
If you do want to have your thermocouple reflect reality, then=3D20
you can program in an offset to compensate - it's pretty=3D20
straightforward on most controllers. If you do replace your=3D20
thermocouple, you will still have to check it, as there is no=3D20
guarantee that it will read correctly, either.
I replaced the thermocouple in the kiln where I teach (not for=3D20
the first time), but unlike its half-dozen predecessors, this=3D20
thermocouple thought that ^8 or 9 was actually ^6. (The error=3D20
increased the hotter the intended cone; it was almost correct=3D20
at ^08.) Our supplier offered to replace the thermocouple, but=3D20
as our firing schedule is quite tight and leaves almost no time=3D20
for test firings, I elected to just program the offset instead. So,=3D20
presently, to get a perfect ^6 on the witness cones I set the kiln=3D20
for ^5, then offset it for 30F degrees cooler than that! I lie to=3D20
the kiln,and it gives me what I want - it's a workable system.=3D20
At the college where I did my grad work, when I first arrived an=3D20
undergrad asked me to show her how to fire the electric kilns.
I showed her how to program the controller (aiming at ^6),=3D20
and told her in general terms how long it ought to take. We put=3D20
in a witness pack, too (though it could't be placed in front of a=3D20
peephole), and started it up. 24 hours later, she called me in=3D20
some distress, as the kiln still hadn't reached temperature! I=3D20
told her to shut it off, and when I came in the next day, we=3D20
checked it. The controller reported at peak temperature of=3D20
2180 F. When we opened it up, the ^7 in the pack was melted=3D20
flat; I han't put in anything higher. So, what the controller=3D20
thought was ^5 or so was likely around ^9 or more. There=3D20
hadn't been a custom at that school of using witness cones=3D20
in electric kilns before that - who knows how long people=3D20
had been putting up with nasty puddled glazes without=3D20
checking, because 'computers are always right'. (The clay=3D20
was fine - when I tested it, the standard studio '^6 clay body'=3D20
turned out to be more like a ^9 recipe.)
Note, though, that there's no reason on earth to try for an=3D20
exact specific cone just because it was designated by some=3D20
label. 'Dead-on ^6' is irrelevant unless that's the heat-work=3D20
your clay and glazes need. If they are better at ^6-1/2, or=3D20
^7 and a smidge, or a low ^8, whatever, then do it. You=3D20
aren't firing a product label or a recipe, you are firing actual=3D20
stuff! Let the materials tell you what they want, and give it to=3D20
them.
-Snail=3D
Josh White on fri 18 feb 11
Cone 6 is not just a temperature, it also accounts for time. Soaking at
peak temperature may not be necessary, especially if the load you are firin=
g
is fairly light (more air than clay). In my experience a more lightly
loaded kiln comes out more fired than a fully loaded kiln. Also, older
elements tend to not reach temperature not over fire. If your thermocouple
is reading the right temperature at room temperature than it is probably
just fine. Glazes will have a more 'washed out' look if they have been ove=
r
fired. I think of it as burning more of the glaze off the work. My guess
is that your kiln is lightly loaded, already firing hotter than you would
like and that the soak is adding to this. I would start by removing the
soak and possibly firing the kiln 10-20 degrees cooler. Best of luck.
Josh White
Production Manager
Syzygy Inc.
Silver City, NM
www.syzygytile.com
Maggie Furtak on fri 18 feb 11
Hey Jen et al,
To everyone else's helpful advise, I'd like to add: I wouldn't think that =
a 10
minute soak could be responsible for over-firing by 2 cones. For my kiln i=
t is
usually a minimum of 20 minutes to get from one cone to the next with the k=
iln
blasting away on high power. It is often more like an hour, depending on h=
ow
many of the neighbors are running their AC and how many pots I have crammed=
in
there. And the higher the cone, the longer it takes to get from one cone t=
o the
next.
I agree with the bumped thermocouple theory.
Whether you replace it, or just make yourself a deviation table and watch c=
ones,
it's a good idea to also keep a kiln log, if you aren't already.
On mine I record how full the kiln was. (The more stuffed, the slower she
goes). I also record the time I start the kiln and the temperature outside=
.
(The other big factor in how long an electric kiln takes to reach temperat=
ure
is how much power is available. When I start the kiln at 6:00 a.m., it is =
done
and off before my neighbors come home from work and start using their
electricity, so I get a faster firing. Also, an exceptionally cold or hot =
day,
means everyone is using lots of electricity to heat or cool their homes. T=
his
results in a slower firing.) Start keeping a record, and in a few months y=
ou'll
be able to look back at your notes to see how long the last firing on a 50
degree day took. If that firing was very full, and the one you are doing
currently is a light load, you can guess it will take a 30 minutes or an ho=
ur
less. Helps you be sure to start checking the cones at the right time, and
schedule your day. (:
Good luck!
-Maggie
(who is bisquing as we speak, and I don't mean making soup)
Pate Ceramics
pateceramics.etsy.com
pateceramics.blogspot.com
781-956-1364
517 Fellsway East
Malden, MA 02148
Arnold Howard on fri 18 feb 11
On 2/17/2011 6:06 PM, Eric Hansen wrote:
> I have seen people fire kilns this way, just turn it "on" with a
> target "temperature" dialed in. This for certain will get different
> results every time. I don't know that it is a recommended method of
> firing by kiln manufacturers, if so - we need to decide what their
> punishment should be for disseminating false information. Any
> thoughts, Arnold??
Cone-Fire mode of Orton and Bartlett controllers is based on the 108F
cone temperatures from the Orton cone chart. During the last hour of
firing, the Cone-Fire programmed rate is 108F per hour.
I've always believed in witness cones. About 10 years ago I taught an
in-service seminar to high school teachers. I asked for a show of hands:
Only two or three teachers out of around 60 even used witness cones in
their digital kilns. That was the first time I discovered that people
don't use cones.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
Jennifer Jeglinski on mon 21 feb 11
I just wanted to thank everyone who took the time to really explain the fir=
=3D
ing process and thermocouples=3D2C cones=3D2C hold times=3D2C etc. Apparent=
ly I h=3D
ave been firing blindly relying only on my temperature gauge and looking at=
=3D
the cones only when I open up the kiln. I am glad up until now that there =
=3D
haven't been any major kiln meltdowns. I can see that it was in the future =
=3D
though if I kept up this way.
=3D20
I always have kept kiln logs monitoring the times and temps=3D2C but not re=
ly=3D
ing on the visual cones. Back in my days of wood firing=3D2C that's all I u=
se=3D
d and kind of thought once I had a digital readout of the temp=3D2C that I =
di=3D
dn't have to think much about it. Clearly=3D2C I was mistaken. Looks like I=
'l=3D
l have to invest in some safety goggles so I can peer into the next firing.=
=3D
=3D20
=3D20
I'm guessing it makes sense to use visual cones for any firing=3D2C even bi=
sq=3D
ues=3D2C huh? And it will be interesting to see how my glaze kiln fires whe=
n =3D
I'm ready sometime next month. I imagine I won't have as much of a problem =
=3D
with running glazes.=3D20
=3D20
with much appreciation=3D2C
Jen
=3D20
> Date: Fri=3D2C 18 Feb 2011 10:04:32 -0800
> From: pateceramics@yahoo.com
> Subject: Re: Cone 6 electric kiln mishap
> To: jenjeglinski4@HOTMAIL.COM=3D3B clayart@lsv.ceramics.org
>=3D20
> Hey Jen et al=3D2C=3D20
>=3D20
> To everyone else's helpful advise=3D2C I'd like to add: I wouldn't think =
th=3D
at a 10=3D20
> minute soak could be responsible for over-firing by 2 cones. For my kiln =
=3D
it is=3D20
> usually a minimum of 20 minutes to get from one cone to the next with the=
=3D
kiln=3D20
> blasting away on high power. It is often more like an hour=3D2C depending=
o=3D
n how=3D20
> many of the neighbors are running their AC and how many pots I have cramm=
=3D
ed in=3D20
> there. And the higher the cone=3D2C the longer it takes to get from one c=
on=3D
e to the=3D20
> next.=3D20
>=3D20
> I agree with the bumped thermocouple theory.=3D20
>=3D20
> Whether you replace it=3D2C or just make yourself a deviation table and w=
at=3D
ch cones=3D2C=3D20
> it's a good idea to also keep a kiln log=3D2C if you aren't already.
>=3D20
> On mine I record how full the kiln was. (The more stuffed=3D2C the slower=
s=3D
he=3D20
> goes). I also record the time I start the kiln and the temperature outsid=
=3D
e.=3D20
> (The other big factor in how long an electric kiln takes to reach tempera=
=3D
ture=3D20
> is how much power is available. When I start the kiln at 6:00 a.m.=3D2C i=
t =3D
is done=3D20
> and off before my neighbors come home from work and start using their=3D2=
0
> electricity=3D2C so I get a faster firing. Also=3D2C an exceptionally col=
d or=3D
hot day=3D2C=3D20
> means everyone is using lots of electricity to heat or cool their homes. =
=3D
This=3D20
> results in a slower firing.) Start keeping a record=3D2C and in a few mon=
th=3D
s you'll=3D20
> be able to look back at your notes to see how long the last firing on a 5=
=3D
0=3D20
> degree day took. If that firing was very full=3D2C and the one you are do=
in=3D
g=3D20
> currently is a light load=3D2C you can guess it will take a 30 minutes or=
a=3D
n hour=3D20
> less. Helps you be sure to start checking the cones at the right time=3D2=
C =3D
and=3D20
> schedule your day. (:=3D20
>=3D20
> Good luck!
> -Maggie
> (who is bisquing as we speak=3D2C and I don't mean making soup)
> Pate Ceramics
> pateceramics.etsy.com
> pateceramics.blogspot.com
> 781-956-1364
> 517 Fellsway East
> Malden=3D2C MA 02148
>=3D20
>=3D20
>=3D20
>=3D20
=3D
Arnold Howard on mon 21 feb 11
On 2/21/2011 3:28 PM, Jennifer Jeglinski wrote:
Looks like I'll have to invest in some safety goggles so I can peer into
the next firing.
Here is a link to firing safety glasses:
http://www.paragonweb.com/Firing_Safety_Glasses.cfm
You can find glasses at Amazon. Look for green #3 lenses.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
| |
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