ilene richardson on tue 11 jan 05
I think I found a goo link to the Orton Cone Firing chart, check this =
out and see if I'm correct. Unless, of course this is one you've =
developed yourself, Arnold.
It could save you some stamps.=20
http://www.kickwheel.com/orton.cone.chart.html
Ilene
Lisa E on tue 7 nov 06
I just got my first kiln so forgive me if this question is basic (or plain
stupid) but if you don't ask, you'll never know right?
My question is, how do you read the Orton Cone Chart? For example, ^6 for
self supporting cones has 3 temperatures next to it: 2165, 2232 and 2269 and
at the top it says 27, 108, 270 with reference to heating rate F/hour(last
180 F of firing).
Q1 - Why are there different cone temps?
Q2 - What does the 27, 108, 270 mean?
Q3 - Can I use this chart to figure out the heating rate (time to bring to
the cone temp) for each cone temp?
Thank you in advance!!!
Lisa E
Mark Tigges on tue 7 nov 06
On Tue, Nov 07, 2006 at 07:58:15AM -0800, Lisa E wrote:
> My question is, how do you read the Orton Cone Chart? For example, ^6 for
> self supporting cones has 3 temperatures next to it: 2165, 2232 and 2269 and
> at the top it says 27, 108, 270 with reference to heating rate F/hour(last
> 180 F of firing).
Cones are calibrated measures of heatwork. Heat work is temperature
integrated over time. (Calculus. It really isn't scary, honest.)
Basically what it means is the area under a graph of temperature
change over time:
>
> Q1 - Why are there different cone temps?
The faster you reach temperature, the less area will be under the
graph. And hence, the less heatwork will have been applied. So if
you want to reach a certain heatwork given some rate, you will have to
adjust the top temperature you reach.
> Q2 - What does the 27, 108, 270 mean?
The three numbers 27 and 108 and 270 refer to rate of change of
temperature (presumably in degrees fahrenheit / hours).
> Q3 - Can I use this chart to figure out the heating rate (time to bring to
> the cone temp) for each cone temp?
Yes, but that isn't how it was meant to be used. The chart shows you
what temperature you need to reach to apply a certain amount of
heatwork given how fast your firing has changed temperature. Since
your kilns rate of temperature will not be linearly, you're going to
be using some best guess as an average anyways.
The chart is nice, and certainly useful, but not an ideal tool to
control the kiln. In my opinion, all one needs is a pyrometer and
some witness cones. But most people these days seem to have their
kiln controlled by a supplied computer into which they program the
schedule. I prefer to turn the dials themselves when they need to be
turned - thereby monitoring the firing, and knowing it is correct.
Mark.
--
http://www.m2crafts.ca
m2crafts [at] gmail
Arnold Howard on tue 7 nov 06
From: "Lisa E"
> Q1 - Why are there different cone temps?
> Q2 - What does the 27, 108, 270 mean?
> Q3 - Can I use this chart to figure out the heating rate
> (time to bring to
> the cone temp) for each cone temp?
The three columns in the Orton temperature chart each
represent a different firing speed. The 27 degree F column =
27 degrees per hour of temperature rise during the last 90 -
120 minutes.
Digital kilns are programmed with cone temperatures from the
108 degree column.
The 27, 108, and 270 degrees per hour rates apply only to
the last 90 - 120 minutes of firing. The earlier part of the
firing can be fast or slow, and the temperatures in the
columns will still apply.
The Orton chart is similar to B&W film developer charts.
Processing time varies depending on developer temperature.
The higher the temperature, the shorter the film processing
time.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
Lisa E on tue 7 nov 06
Thank you Mark & Arnold for your responses!!!
On 11/7/06, Mark Tigges wrote:
>
> On Tue, Nov 07, 2006 at 07:58:15AM -0800, Lisa E wrote:
> > My question is, how do you read the Orton Cone Chart? For example, ^6
> for
> > self supporting cones has 3 temperatures next to it: 2165, 2232 and 2269
> and
> > at the top it says 27, 108, 270 with reference to heating rate
> F/hour(last
> > 180 F of firing).
>
> Cones are calibrated measures of heatwork. Heat work is temperature
> integrated over time. (Calculus. It really isn't scary, honest.)
> Basically what it means is the area under a graph of temperature
> change over time:
>
> >
> > Q1 - Why are there different cone temps?
>
> The faster you reach temperature, the less area will be under the
> graph. And hence, the less heatwork will have been applied. So if
> you want to reach a certain heatwork given some rate, you will have to
> adjust the top temperature you reach.
>
> > Q2 - What does the 27, 108, 270 mean?
>
> The three numbers 27 and 108 and 270 refer to rate of change of
> temperature (presumably in degrees fahrenheit / hours).
>
> > Q3 - Can I use this chart to figure out the heating rate (time to bring
> to
> > the cone temp) for each cone temp?
>
> Yes, but that isn't how it was meant to be used. The chart shows you
> what temperature you need to reach to apply a certain amount of
> heatwork given how fast your firing has changed temperature. Since
> your kilns rate of temperature will not be linearly, you're going to
> be using some best guess as an average anyways.
>
>
>
>
> The chart is nice, and certainly useful, but not an ideal tool to
> control the kiln. In my opinion, all one needs is a pyrometer and
> some witness cones. But most people these days seem to have their
> kiln controlled by a supplied computer into which they program the
> schedule. I prefer to turn the dials themselves when they need to be
> turned - thereby monitoring the firing, and knowing it is correct.
>
> Mark.
>
> --
> http://www.m2crafts.ca
> m2crafts [at] gmail
>
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
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> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
--
Lisa E
Sunny Daze Design Pottery Studio
Squamish, BC
Snail Scott on tue 7 nov 06
At 07:58 AM 11/7/2006 -0800, you wrote:
>My question is, how do you read the Orton Cone Chart? For example, ^6 for
>self supporting cones has 3 temperatures next to it: 2165, 2232 and 2269=
and
>at the top it says 27, 108, 270 with reference to heating rate F/hour(last
>180 F of firing).
>
>Q1 - Why are there different cone temps?
Because cones do not actually measure temperature;=20
they really measure heat-work, which is the result=20
of temperature _acting on materials over time_.=20
If some food is cooked properly if heated to 350=BAF=20
for an hour, will you get the same result if you=20
cook it to 350=BAF for 45 minutes? No, and that is=20
the concept behind heat-work. Heat alone is only=20
one factor; time is the other, and to a limited=20
extent, one can substitute for the other. So, that=20
45 minute cooking time might work out OK at 375=BA,=20
for instance. Or even at 325=BA for an hour and a=20
half. But not at 200=BA for three hours, or 500=BA=20
for ten minutes. It's gotta be in the ballpark.
The reason that rate of heating only matters for
the last few hundred degrees is that prior to that=20
point, nothing has melted enough to start its=20
chemical reactions and intermingling of materials.=20
You can fire for a week at 1000=BAF, and it won't=20
melt your ^6 glaze. You've got to be close enough=20
for significant melting to occur, for time to start=20
mattering.
>Q2 - What does the 27, 108, 270 mean?
>Q3 - Can I use this chart to figure out the heating rate (time to bring to
>the cone temp) for each cone temp?
That's not what it's for. How fast you reach a=20
given temperature depends on how fast you fire=20
your kiln. But if you know how fast that is,=20
(i.e. with a pyrometer) you can cross-correlate=20
that pyrometer reading to an actual cone number.=20
If you fired to 2165=BAF, that would only get=20
appropriate results from ^6 materials if it=20
was fired slowly - however many degrees per=20
minute are noted at the top of that column.=20
If you fired it faster, you could reach the=20
same temperature, but not the cone, i.e. not=20
the same amount of heat-work. The clay would be=20
underfired, even though the same temperature=20
was reached. If you fired to 2269=BAF, you would=20
reach ^6 at that point if you fired at the=20
fastest rate noted on the chart, but if you=20
fired slowly, you might actually reach ^7 or=20
even ^8 at that point. More heat-work would=20
have occurred, and the clay would be overfired.
Remember, the speed of firing only affects=20
heat-work after the kiln is hot enough to melt=20
the materials you are using.
We often casually talk about the 'temperature'=20
of a firing or a cone, but we ALWAYS really=20
mean heat-work. Even if we judge our firings=20
by using only a pyrometer, we take time into=20
account as it's represented by those charts,=20
to get the proper heat-work required.
-Snail
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