Snail Scott on fri 18 may 01
At 02:30 PM 5/18/01 -0400, you wrote:
i want to know WHO invented pyrometric cones and how did they know
>stuff was fired high enough before they had such things (to say nothing of
>kiln setters and computers!).
>roberta miller
There's lots of info on this, but in a nutshell:
Hermann Seger invented cones in the late 1800's.
(There were cone-type things before, but not
scientifically calibrated ones.)
Before cones, there were draw rings, but mostly
people fired by color. This can actually be fairly
accurate, once you train your eye. It's good to
try to do anyway; I've saved firings where the
cones were destroyed or shifted, by shutting down
at my best guess of temperature, based on what
color that temperature should be. (Most glazes
aren't really that picky; I figure the ones that
are just weren't used in those days.)
Pay attention to the color of your kiln at bisque
temperature, and at glaze-fire temperature. Play
'guessing games' before you check your cones or
pyrometer, and see how closely you can train your
eye. (You may never need to know, but at least
you'll be able to impress your friends with this
'stupid human trick'!)
-Snail
Kevin H. Miller on fri 18 may 01
someone is curious about what kickwheels looked like long ago.
well, i want to know WHO invented pyrometric cones and how did they know
stuff was fired high enough before they had such things (to say nothing of
kiln setters and computers!).
one of those questions that you dream up while driving through the country
in the spring.
roberta miller
Charles Moore on fri 18 may 01
Roberta,
Check with Tim Fredrich at Fredrich@ortonceramics.com. He knows all there
is about cone history.
Charles Moore
Sacramento, CA
> well, i want to know WHO invented pyrometric cones and how did they know
> stuff was fired high enough before they had such things (to say nothing of
> kiln setters and computers!).
> roberta miller
>
>
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Earl Brunner on fri 18 may 01
I know that before cones ONE of the ways to check the progress of a
firing was to pull draw rings out of the kiln. Salt, and I would
suspect soda firing, people still do.
Kevin H. Miller wrote:
> someone is curious about what kickwheels looked like long ago.
> well, i want to know WHO invented pyrometric cones and how did they know
> stuff was fired high enough before they had such things (to say nothing of
> kiln setters and computers!).
>
> one of those questions that you dream up while driving through the country
> in the spring.
>
> roberta miller
>
> ______________________________________________________________________________
> 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.
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
Matt MacIntire on fri 18 may 01
Kevin wrote:
>> WHO invented pyrometric cones and how did they know stuff was fired high
enough before they had such things
The invention of pyrometric cones is generally attributed to Dr. Hermann
Seger in 1886
I recollect that Seger cones were conical instead of trigonal pyramids. I
also think Seger cones are supposed to point straight up. Eventually they
would collapse, rather than tipping like Orton cones. [I think I am
remembering that correctly...??]
One way to gauge the firing process without cones would be to pull draw
tiles, or rings. In salt kilns this is very common. Hook out a ring, cool
it in a bucket of water, examine the glaze coating. This same process could
easily be used to gauge the melt of any glaze and the hardness of the clay
body.
Lots of experience with how the kiln looks and acts would probably also be
sufficient to gauge a firing's progress. Certainly pyrometric cones make
judging an exact endpoint much easier, but lots of glazes have a wide enough
firing range that an experienced person could wing it.
Matt
John Hesselberth on fri 18 may 01
Hi Roberta,
Pyrometric cones were invented by Hermann Augustus Seger in the late 1800s.
You can read the details in and article titled "Pyrometers and Measurement
of High Temperatures. Standard Cones" in The Collected Writings of Hermann
A. Seger, Volume 1, pages 224-249. The English translation was edited by
Albert Bleininger and published by the American Ceramic Society in 1902.
Also contained in Volume 2 are some paper written by Seger and others
challenging, defending and complimenting the work. It is a fun set of books
to get hold of; it is one of my prizes I found on the used book market a
couple years ago. Seger was a genius of his time; much of his work has held
up for over a hundred years now.
Regards,
John
Web site: http://www.frogpondpottery.com Email: john@frogpondpottery.com
"The life so short, the craft so long to learn." Chaucer's translation of
Hippocrates, 5th cent. B.C.
> From: "Kevin H. Miller"
> Reply-To: Ceramic Arts Discussion List
> Date: Fri, 18 May 2001 14:30:58 -0400
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: another potting history question
>
> someone is curious about what kickwheels looked like long ago.
> well, i want to know WHO invented pyrometric cones and how did they know
> stuff was fired high enough before they had such things (to say nothing of
> kiln setters and computers!).
>
> one of those questions that you dream up while driving through the country
> in the spring.
>
> roberta miller
>
> ______________________________________________________________________________
> 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.
Janet Kaiser on sat 19 may 01
From: Kevin H. Miller:
> i want to know WHO invented pyrometric cones and how
did they know
> stuff was fired high enough before they had such
things (to say nothing of
> kiln setters and computers!).
Not often do I get to answer a technical question, so
please bare with me!
Remember there are two fundamentally different methods
of controlling the temperature of kilns:
1. it is measured using pyrometers, etc. which indicate
the exact temperature prevailing in the kiln at any
given time
2. the effect of heat is observed.
To appreciate the difference, consider this: the work
done by heat is dependent not only on the temperature
to which the pots are subjected, but also on the
*duration* they are subjected to any given temperature.
Take a porcelain body in a glaze firing. If the heat is
increased slowly at 50 oC per hour to a final
temperature of 1300 oC, the body will be properly
vitrified and covered with a transparent glaze.
However, if the temperature is raised to the same
temperature in steps of 500 oC per hour, the body may
be porous and the glaze still opaque. The pyrometer
will record that the first firing reached 1300 oC after
26 hours and the second after 2 1/2 hours. In both
cases it will not indicate whether or not the ware has
vitrified.
We can therefore take it that the Old Timers would fire
by experience. Whether slowly increasing the heat over
many hours and even days until the temperature was
reached and then cooling over the same time before
opening the kilns (as in Japan) or much quicker for the
salt-glazed stoneware of Germany... Whether fast or
slow these "periodic kilns" have been used for
centuries with little fundamental change, whatever the
design or type we refer to. Each master "kilnsman" knew
his pots, materials, kiln and fuel after years of
practice. After all, most ceramics where once-fired...
A biscuit followed by a second glaze firing is a
relatively "modern" invention. Just think... even
today, Raku is still fired without the need of
pyrometers or any other aid.
Finally the invention of pyrometric cones: I hope this
extract from "Pottery and Ceramics" by Ernst Rosenthal,
written in 1946 and first published in 1949 helps:
"The use of cones made of different ceramic mixtures
for heat recording was introduced by Seger (Staatlich
Porzellan-Manufactur, Berlin). These cones are called
'Seger cones'. They take the form of a three-sided
pyramid and depending upon their particular
compositions, they become soft and bend over at
different temperatures. The 'squatting' temperature of
the cone is reached when its apex is level with its
base. There is a complete range of these cones and
their composition is chosen in such a way that the
'squatting' temperature of tone cone is 20-30 oC lower
than the 'squatting' temperature of the cone with the
next higher number."
"In this country (UK) Messrs Harrison & Son, Hanley,
Stoke-on-Trent, manufacture Staffordshire Seger cones.
The cone numbers correspond to the temperatures given
for Seger cones.
"In the United States Seger cones have been modified
and are called 'Orton' cones."
Remember this was 1949! Sadly Seger cones are no longer
available in the UK. I know several potters who miss
them very much indeed.
Janet Kaiser - Blushing hard at Veena's report on her
visit to the UK... It was, after all, OUR pleasure to
meet and entertain such a gracious lady and it is only
right that Veena's tile is in The International
Potters' Path. There cannot be many potters who have
lived on at least three Continents!
The Chapel of Art . Capel Celfyddyd
HOME OF THE INTERNATIONAL POTTERS' PATH
Criccieth LL52 0EA, GB-Wales Tel: (01766) 523570
E-mail: postbox@the-coa.org.uk
WEBSITE: http://www.the-coa.org.uk
Frederich, Tim on mon 21 may 01
Roberta,
The first work on pyrometric cones was done by Dr. Herman Seger in Germany
around the period of 1870-1880. Edward Orton Jr. saw these cones in the the
early 1890's. He went on to develop his series and produce them commercially
in 1896. He also began deformation and temperature studies and these are
registered at the National Bureau of Standards in Washington, D.C.
Before the development of cones, kilns were fired by color and test trials
drawn from the kiln. A good kiln fireman was very valuable and paid a decent
wage compared to other people in the industry. Cones deform based on time
and temperature and have a very exact repeatable quality which the eye could
not always judge. The use of cones saved a lot of product loss, increased
production and allowed financial rewards.
Best regards,
Tim Frederich, Orton Ceramic Foundation
-----Original Message-----
From: Kevin H. Miller [mailto:cn1919@COASTALNET.COM]
Sent: Friday, May 18, 2001 2:31 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: another potting history question
someone is curious about what kickwheels looked like long ago.
well, i want to know WHO invented pyrometric cones and how did they know
stuff was fired high enough before they had such things (to say nothing of
kiln setters and computers!).
one of those questions that you dream up while driving through the country
in the spring.
roberta miller
____________________________________________________________________________
__
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.
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