MOLINA, RAFAEL on thu 7 feb 02
I just received "Mastering Cone 6..." via UPS today. KUDOS TO RON AND =
JOHN FOR A GREAT BOOK. I will be able to use it for my cone 6 oxidation =
explorations and I believe it will also help in my experimentations at =
cone 10 oxidation. I am going to immediately place it on my Books On =
Reserve list in the Library for my students.
Cone 6 oxidation has been a part of my ceramics course syllabus for the =
last 8 years. Before that time my experience with electric kilns was =
limited to bisque firing and a few attempts with maiolica. In January =
1994 I took a job as adjunct at Navarro College and the only kiln =
available was an old square top loading Paragon High Fire. I took it as =
a challenge to develop a curriculum that would utilize only oxidation =
firing in an electric kiln. Within that limitation I came up with =
creative exercises that included the following types of surface =
finishing: saggar firing at ^ 012, Clear glaze (Satellite Diamond Clear =
Gloss) over Amaco Velvet Underglazes at ^ 06, maiolica at ^ 03, colored =
clay at ^ 2, glazes at ^ 6, and glazes at ^ 10. As you can see a =
variety of finishing processes are available in spite of narrow choices =
with regard to equipment.
When I moved to my present situation in 1999 I encountered the same =
scenario. For the first three years of the program here at Southeast we =
only had electric kilns in which to fire so I used the same curriculum. =
When we move in to our new facility we will have reduction, raku, =
salt/soda, and wood available to fire our work, but I will continue =
firing in oxidation as a regular part of my course.
One reason I think oxidation firing should be an integral part of any =
college ceramics curriculum is that the electric kiln is a piece of =
equipment that is economically feasible to purchase for those students =
wishing to set up a studio at home. In addition to price, the space =
necessary to house an electric kiln is probably more readily available =
to students as well. Furthermore, municipal ordinances are probably =
easier to comply with by installing an electric kiln rather than a =
fossil fuel burning kiln.
The subject line refers to my question about the firing temperature of =
2232 F. Historically, ware has been fired at very low temperatures in =
pits or above ground mounds/bonfires where the clay bodies didn't even =
approach maturity or in fuel kilns that reached earthenware claybody =
maturing temperatures 2015 F or fuel kilns that fired to stoneware and =
porcelain claybody maturing temperatures of around 2381 F and above.
It's only been a recent development to fire at the "mid-temperature" of =
cone 6. I'm curious about exactly how did we arrive at that =
temperature? It's commonly accepted that earthenware or stoneware and =
porcelain claybodies are more "natural" and relatively easy to formulate =
with regard to color, texture, plasticity, shrinkage, and porosity? =
Are not "mid-fire" bodies a sort of recent "invention"?
I'm only playing the "Devil's Advocate" here to generate some discussion =
on the topic of cone 6 clays, glaze, and firing. In no way am I =
impugning anyone's integrity or work. (It annoy's me to have to include =
this disclaimer, but some folks on this List just can't read).
Chao,
Rafael Enrique =20
Rafael Molina, MFA
Assistant Professor of Art
Department of Music, Art, and Dance
Tarrant County College-Southeast Campus
2100 Southeast Parkway
Arlington, TX 76018-3144
(817) 515-3711
(817) 515-3189 fax
Greg Lamont on fri 8 feb 02
Rafael,
IMHO, I think the reason cone 6 was chosen as the temperature for midrange
stoneware is twofold. First, it's relatively easy to adapt a cone 10
stoneware to mature at cone 6 simply by adjusting the ratio of fluxing
materials to clays. No exotic (read costly) fluxing materials are needed at
this temperature.
Secondly, cone 6 is really the practical upper limit of the the typical
electric kiln available to the home user. For example, I have an L&L J-230
purchased in 1983. It's rated at cone 10, however with only 2.5" brick
thickness in the wall (and no other jacket of insulating materials) and no
elements in the floor, I believe the journey to cone 10 would be a long and
expensive one. Nowdays, a top-loading kiln rated to cone 10 typically has 3"
brick thickness or additional fiber insulating jacket between the brick and
the outer shell, and floor elements--options that were generally not
available in this type of kiln twenty years ago. Kilns like mine are now
generally rated between cones 6 and 8.
Greg
----Original Message-----
From: MOLINA, RAFAEL
To: CLAYART@LSV.CERAMICS.ORG
Date: Friday, February 08, 2002 1:08 AM
Subject: Why Cone 6 At All?
>I just received "Mastering Cone 6..." via UPS today. KUDOS TO RON AND =
>JOHN FOR A GREAT BOOK. I will be able to use it for my cone 6 oxidation =
>explorations and I believe it will also help in my experimentations at =
>cone 10 oxidation. I am going to immediately place it on my Books On =
>Reserve list in the Library for my students.
>
>Cone 6 oxidation has been a part of my ceramics course syllabus for the =
>last 8 years. Before that time my experience with electric kilns was =
>limited to bisque firing and a few attempts with maiolica. In January =
>1994 I took a job as adjunct at Navarro College and the only kiln =
>available was an old square top loading Paragon High Fire. I took it as =
>a challenge to develop a curriculum that would utilize only oxidation =
>firing in an electric kiln. Within that limitation I came up with =
>creative exercises that included the following types of surface =
>finishing: saggar firing at ^ 012, Clear glaze (Satellite Diamond Clear =
>Gloss) over Amaco Velvet Underglazes at ^ 06, maiolica at ^ 03, colored =
>clay at ^ 2, glazes at ^ 6, and glazes at ^ 10. As you can see a =
>variety of finishing processes are available in spite of narrow choices =
>with regard to equipment.
>
>When I moved to my present situation in 1999 I encountered the same =
>scenario. For the first three years of the program here at Southeast we =
>only had electric kilns in which to fire so I used the same curriculum. =
>When we move in to our new facility we will have reduction, raku, =
>salt/soda, and wood available to fire our work, but I will continue =
>firing in oxidation as a regular part of my course.
>
>One reason I think oxidation firing should be an integral part of any =
>college ceramics curriculum is that the electric kiln is a piece of =
>equipment that is economically feasible to purchase for those students =
>wishing to set up a studio at home. In addition to price, the space =
>necessary to house an electric kiln is probably more readily available =
>to students as well. Furthermore, municipal ordinances are probably =
>easier to comply with by installing an electric kiln rather than a =
>fossil fuel burning kiln.
>
>The subject line refers to my question about the firing temperature of =
>2232 F. Historically, ware has been fired at very low temperatures in =
>pits or above ground mounds/bonfires where the clay bodies didn't even =
>approach maturity or in fuel kilns that reached earthenware claybody =
>maturing temperatures 2015 F or fuel kilns that fired to stoneware and =
>porcelain claybody maturing temperatures of around 2381 F and above.
>
>It's only been a recent development to fire at the "mid-temperature" of =
>cone 6. I'm curious about exactly how did we arrive at that =
>temperature? It's commonly accepted that earthenware or stoneware and =
>porcelain claybodies are more "natural" and relatively easy to formulate =
>with regard to color, texture, plasticity, shrinkage, and porosity? =
>Are not "mid-fire" bodies a sort of recent "invention"?
>
>I'm only playing the "Devil's Advocate" here to generate some discussion =
>on the topic of cone 6 clays, glaze, and firing. In no way am I =
>impugning anyone's integrity or work. (It annoy's me to have to include =
>this disclaimer, but some folks on this List just can't read).
>
>Chao,
>
>Rafael Enrique =20
>
>
>Rafael Molina, MFA
>Assistant Professor of Art
>Department of Music, Art, and Dance
>Tarrant County College-Southeast Campus
>2100 Southeast Parkway
>Arlington, TX 76018-3144
>(817) 515-3711
>(817) 515-3189 fax
>
>___________________________________________________________________________
___
>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.
>
Khaimraj Seepersad on fri 8 feb 02
Good Day to All ,
Greg , Rafael ,
I always looked at it as -
Local Earthenwares extended with Talc
/ Mica [ Mica schists as we say down here ]
[ going from 1130 deg.c to 1200 deg.c ]
Or spin-offs of Behren's bodies for cone 6
using Ball Clay , China Clay , Talc , Nepheline
Syenite and Flint [ Silica ? ].
Easily obtained materials and cheap.
and
B203 added [ properly balanced ] glazes.
1280 glazes going to 1200 deg.c ]
There is at least one glaze where you can
add a Parmelee noted Artificial G.B to
70 % Nc4 Feldspar and mature a glaze at
980 deg.c [ 14.9 % B203 and 6.7 Alkali ].
Wouldn't take much to decrease the B203
and regain Cone 6.
There is also a glaze combination out of
Australia , using Feldspar , Talc , Silica ,
Kaolin , Calcium Carbonate that registered
for cone 6 , but I figure a touch of B203
would improve the melting.
As to raw glazes , there is one for 950 deg.c
but it fits nothing , I can come up with .
It is also Soda Ash , Feldspar , Calcium
Carbonate and Silica.Then you shift over to
Lithium Carbonate.
From what I have been watching , it is
convenience.
After Cone 6 , fritted materials come into
play and the cost goes up.
Frit versus Feldspar , per bag.
I have noted some unusual results for terra
sigillata type clay to fuse and become vitreous
at cone 06 [ orton small cone ] but that is an
odd pocket I come across down here once in
a while. Though I believe The Hamers do speak
of a white pipe clay , doing the same.
Khaimraj
Paul Lewing on fri 8 feb 02
Rafael,
I once heard Pete Pinnell, in a lecture at NCECA, talk about the origins of
the cone 6 temperature range. He basically said it was a compromise,
brought about by the invention and popularity of the top-loading electric
kiln. Cone 6 was the highest practical temperature limit for the elements
and amount of insulation that most electric kilns use. And in my opinion,
Pete's a genius, and I believe every word he says.
Another of his points was that clay that matures at cone 6 occurs naturally
nowhere in the world. The world is full of low-fire clay, especially red
low-fire clay. It's literally as common as dirt. And there are very, very
common materials that can be used to make glazes that will melt at that
temperature, like lead, boron and sodium. Then there are a few places in
the world where high-fire stoneware and porcelain clays occur naturally, and
there are a multitude of materials that can be used to make glazes at that
temperature, like whiting, talc, feldspar, flint, even that common red
low-fire clay. But clay for cone 6 has to be blended. It has to be made by
fluxing down a high-fire clay, or adding refractories to a low-fire clay.
The same is true of the glazes. They generally are much more complex and
trickier to use, because they need to be balances of the low-fire and the
high-fire stuff.
So it's cone 6 because potters wanted to make the most durable pots they
could in their electric kilns. It's also the reason that almost everyone
who's doing cone 6 is firing in oxidation. Generally any gas kiln that will
go to cone 6 will also go to cone 9 or 10. People tend not to fire to cone
6, or lower, in their gas kilns in reduction simply because they don't know
people who do.
Someone said it's cone 6 because it's pretty easy to adapt cone 10 glaze
recipes to cone 6. That has never been my experience, especially if you
also make the atmosphere switch, too. Actually, maybe I shouldn't say that.
When I made the switch I went to 5, not 6, and have since dropped to cone 4.
Believe me, you have no hope of adapting cone 10 recipes to cone 4!
Paul Lewing, Seattle
Roger Korn on sat 9 feb 02
Yes indeed! Pete's utterances have the highest info to BS ratio I've encountered. I
can't make his copper reds fail, no matter how sloppy I get about my firing cycles.
Roger, waiting for naked weather in the Verde Valley.
Paul Lewing wrote:
> on 2/9/02 6:59 AM, Roger Korn at rogerk1941@EARTHLINK.NET wrote:
>
> > Just a fortuitous combination gives us reddish ^6 clays, but they ARE natural.
> > I
> > really doubt that any of the local PRIMARY deposits would fire that high,
> > however.
>
> >> I once heard Pete Pinnell, in a lecture at NCECA, talk about the origins of
> >> the cone 6 temperature range. ...And in my opinion,
> >> Pete's a genius, and I believe every word he says.
> >> Another of his points was that clay that matures at cone 6 occurs naturally
> >> nowhere in the world. ...
>
> Well, there you go, Roger. As Oliver Wendell Holmes said, "All
> generalizations are false, including this one". I believe you on this one,
> but I still feel the same way about Pete.
> Paul Lewing, Seattle
>
> ______________________________________________________________________________
> 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.
--
Roger Korn
McKay Creek Ceramics
In AZ: PO Box 463
4215 Culpepper Ranch Rd
Rimrock, AZ 86335
928-567-5699 <-
In OR: PO Box 436
31330 NW Pacific Ave.
North Plains, OR 97133
503-647-5464
Roger Korn on sat 9 feb 02
Hi Paul,
Come on down to the Verde Valley of AZ, where everything in the soil is full of
limestone. Our local plastic red clays are made less plastic by the limestone they
pick up. You look at the clay and say, "Ah, yet another ^06 iron-rich clay." But it
matures at mid-ranges temps, because of the high calcia content. Even the local
feldspars from the decomposing granites tend towards the calcia end of the
plagioclase family, and make good ^10-12 fluxes.
Just a fortuitous combination gives us reddish ^6 clays, but they ARE natural. I
really doubt that any of the local PRIMARY deposits would fire that high, however.
Roger
Paul Lewing wrote:
> Rafael,
> I once heard Pete Pinnell, in a lecture at NCECA, talk about the origins of
> the cone 6 temperature range. ...And in my opinion,
> Pete's a genius, and I believe every word he says.
> Another of his points was that clay that matures at cone 6 occurs naturally
> nowhere in the world. ...
> Paul Lewing, Seattle
>
> ______________________________________________________________________________
> 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.
--
Roger Korn
McKay Creek Ceramics
In AZ: PO Box 463
4215 Culpepper Ranch Rd
Rimrock, AZ 86335
928-567-5699 <-
In OR: PO Box 436
31330 NW Pacific Ave.
North Plains, OR 97133
503-647-5464
Paul Lewing on sat 9 feb 02
on 2/9/02 6:59 AM, Roger Korn at rogerk1941@EARTHLINK.NET wrote:
> Just a fortuitous combination gives us reddish ^6 clays, but they ARE natural.
> I
> really doubt that any of the local PRIMARY deposits would fire that high,
> however.
>> I once heard Pete Pinnell, in a lecture at NCECA, talk about the origins of
>> the cone 6 temperature range. ...And in my opinion,
>> Pete's a genius, and I believe every word he says.
>> Another of his points was that clay that matures at cone 6 occurs naturally
>> nowhere in the world. ...
Well, there you go, Roger. As Oliver Wendell Holmes said, "All
generalizations are false, including this one". I believe you on this one,
but I still feel the same way about Pete.
Paul Lewing, Seattle
| |
|
