Clay art on thu 31 may 12
Hi Guys. As many of you know I am working with SI and other highly
translucent porcelains. Ever since I started the "cutting and pasting"
processes, I noticed that the clay makes a little ridge in the final
firing(like slip casting would do if the seams are not finished off
correctly), just there where I did the attachment. As I smooth the surface
out after I added multiple pieces of clay to build the shape I lose track o=
f
where the seams are and then end up with these little ridges in otherwise
smooth surfaces.
I got the advice to cross-attach before, but sometimes the clay is so thin,
that I have to grab all the surface I could get to attach.
Another, somewhat related problem that I have is that when I do succeed to
fix a crack, it smooth out and does not show up as a ridge, but when I hol=
d
it against light, it shows the crack in the wall of the pot. (is that what
glass would do too, and why?)
So I've been thinking why the clay is doing that and my only conclusion thi=
s
far is that there must be deflocculants in the clay to prevent the clay fro=
m
getting "dead" , maybe to extend the shelf life. I am correct in my
assumption, I wonder what would happen if I add a flocculant to the clay
that I am working with at that moment. I have to mention that I add a squir=
t
of vinegar to my clay water when I throw. It helps forming a layer of slip
on the walls to thin the walls better.
Then I am also wondering if I am making too big of a deal of this. In my
kind of work, tiny cracks and irregularities seems to be the norm, or is
that just an excuse for sloppy work?
Just wondering....
Antoinette Badenhorst
www.porcelainbyAntoinette.com
P.S. My daughter is doing very well on the Food Network Show. You can watc=
h
the program on Sunday and Wednesday nights and vote on www.Foodnetwork.com
She is the blond with the curly hair and the big smile!
Clay art on sat 2 jun 12
Problem is Fred that the ridges I am talking about only coming out in the
final firing. I do sand my work before I glaze fire.
Antoinette Badenhorst
www.PorcelainbyAntoinette.com
-----Original Message-----
From: Fredrick Paget [mailto:fredrick@well.com]
Sent: Friday, June 01, 2012 10:47 PM
To: Clay art
Subject: Re: A question for porcelain scientists among us.
>Hi Guys. As many of you know I am working with SI and other highly
>translucent porcelains. Ever since I started the "cutting and pasting"
>processes, I noticed that the clay makes a little ridge in the final
>firing......
>Antoinette Badenhorst
In working with SI (which I consider to be the world's nastiest clay to
work with but the most beautiful) I have sometimes prebisqued it to cone
020. That leaves it soft enough so you can still work on it with carbide
scrapers and Scotch Brite or sand paper. Then give it another firing to
bisque and proceed. That way you can get rid of the ridges . Soak it in
water before sanding with wet or dry sandaper to prevent dust.
Fred Paget
--
Twin Dragon Studio
Mill Valley, CA, USA
Fredrick Paget on sun 3 jun 12
>Lee Love asks "What is S1?
>
It is Southern Ice porcelain.
It contains a pure white clay mineral from New Zealand called
halosite instead of kaolin .It is beautiful if you master it but it
is not for the faint of heart - cracks, slumping and lack of
plasticity are features. It specializes in cracking. It is made into
a clay body in Australia and is hard to get and expensive.
Dr. Carty of Alfred University advised me not to use it. I think
that it is a challange so I keep fooling with it.
But if you can master it it is so beautiful! Antonette has pretty
well mastered it but even she still has problems.
Fred Paget
--
Twin Dragon Studio
Mill Valley, CA, USA
Lee on sun 3 jun 12
What is S1?
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is, =3D
"The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Vinod Chettur on mon 4 jun 12
Southern Ice porcelain.
Clay art on thu 7 jun 12
Oh finally some answers on my question. I wonder if it is possible that the
platelets may have something to do with the tiny ridges that fires out at
the joints. I cannot treat it like joints on slip casting, since I loses th=
e
joints during the making process. I do not burnish........Southern Ice is
fairly "open" with lesser plastic qualities.
Antoinette Badenhorst
www.porcelainbyAntoinette.com
-----Original Message-----
From: Clayart [mailto:Clayart@LSV.CERAMICS.ORG] On Behalf Of Fredrick Paget
Sent: Thursday, June 07, 2012 12:18 PM
To: Clayart@LSV.CERAMICS.ORG
Subject: Re: A question for porcelain scientists among us.
Joel Browne writes:
>Hello - I happened to stumble across this site and subject. I hope it
>is OK if I comment about :
>"It is Southern Ice porcelain.It contains a pure white clay mineral
>from New Zealand called halosite instead of kaolin."
>
>I am a studio potter living in Kerikeri, which is the nearest town to
>the where NZ halloysite is minded.
>
>It is true this material is a very pure, and very white clay mineral.
>But ,it is called halloysite and not halosite. It is a kaolin, although
>it is not kaolinite. It is used in some of the very best porcelain and
>bone china, but when I have previously asked people at the mine I was
>told that Southern Ice Porcelain does not contain any NZ halloysite.
Ah, the mystery deepens! Since Southern Ice is made in Australia they ma=
y
be getting the halloysite from Australia. ?? Or maybe it does not contain i=
t
at all! We even have some yellow halloysite in USA so it is widespread.
Dr. Carty told me that halloysite is made up of curled plates while
kaolinite is of flat plates , so it is different from what we call just
"kaolin". You are right in that it is technically a kaolin.
Sorry about the misspellings .I am spelling challenged so I usually let
my wife proof read for me. I can usually spot words that are wrong but ofte=
n
can not get them right, The spell checker on my mail program (Eudora) is
busted so I am on guard.
Fred Paget
--
Twin Dragon Studio
Mill Valley, CA, USA
Joel Browne on thu 7 jun 12
Hello - I happened to stumble across this site and subject. I hope it is =
=3D
OK
if I comment about <=3D
e
clay mineral from New Zealand called halosite instead of kaolin.>>
I am a studio potter living in Kerikeri, which is the nearest town to the=
=3D
where NZ halloysite is minded.
It is true this material is a very pure, and very white clay mineral. But=
=3D
,
it is called halloysite and not halosite. It is a kaolin, although it is =
=3D
not
kaolinite. It is used in some of the very best porcelain and bone china, =
=3D
but
when I have previously asked people at the mine I was told that Southern =
=3D
Ice
Porcelain does not contain any NZ halloysite.
Fredrick Paget on thu 7 jun 12
Joel Browne writes:
>Hello - I happened to stumble across this site and subject. I hope it is O=
K
>if I comment about :
>"It is Southern Ice porcelain.It contains a pure white
>clay mineral from New Zealand called halosite instead of kaolin."
>
>I am a studio potter living in Kerikeri, which is the nearest town to the
>where NZ halloysite is minded.
>
>It is true this material is a very pure, and very white clay mineral. But
>,it is called halloysite and not halosite. It is a kaolin, although it is =
not
>kaolinite. It is used in some of the very best porcelain and bone china, b=
ut
>when I have previously asked people at the mine I was told that Southern I=
ce
>Porcelain does not contain any NZ halloysite.
Ah, the mystery deepens! Since Southern Ice is made in Australia
they may be getting the halloysite from Australia. ?? Or maybe it
does not contain it at all! We even have some yellow halloysite in
USA so it is widespread.
Dr. Carty told me that halloysite is made up of curled plates while
kaolinite is of flat plates , so it is different from what we call
just "kaolin". You are right in that it is technically a kaolin.
Sorry about the misspellings .I am spelling challenged so I usually
let my wife proof read for me. I can usually spot words that are
wrong but often can not get them right, The spell checker on my mail
program (Eudora) is busted so I am on guard.
Fred Paget
--
Twin Dragon Studio
Mill Valley, CA, USA
Bryan Johnson on thu 7 jun 12
On Thu, May 31, 2012 at 10:49 AM, Clay art wrote=
:
> Hi Guys. As many of you know I am working with SI and other highly
> translucent porcelains. Ever since I started the "cutting and pasting"
> processes, I noticed that the clay makes a little ridge in the final
> firing(like slip casting would do if the seams are not finished off
> I'd guess it s a particle packing and alignment issue. Do you burnish the
> area?
I don't know if this would help.
Bryan Johnson
Johanna Demaine on fri 8 jun 12
Hi Antoinette
Just to put the record straight, the following is an extract from "Porcel=
=3D
ain and=3D20
Bone China" by Sasha Wardell.
"Les Blakebrough (Australia) has produced a produced a porcelain clay wit=
=3D
h=3D20
particularly white, translucent qualities. Southern Ice Porcelain derives=
=3D
its name=3D20
from the area it was generated-Hobart, Tasmania, which is one of the=3D20
southernmost parts of the Southern Hemisphere. It was developed over a=3D2=
0=3D
period of six years by a small team of associates with the support of the=
=3D
=3D20
Australian Research Council and the University of Tasmania. Since the=3D20=
=3D
commercial release by Clayworks of Dandenong, Victoria, the clay is now b=
=3D
eing=3D20
exported to several countries including th UK and USA.
One of the issues that drove this research was the fact that Blakebrough=3D=
20=3D
wanted a clay that would stand up to scrutiny even if it remained unglaze=
=3D
d.=3D20=3D20
Being dissatisfied with what was currently available, he embarked on the=3D=
20=3D
Southern Ice Project, attempting to use the local raw materials. Kaolin=3D=
20=3D
deposits found at Tonganah, near Scottsdale, were already being used in a=
=3D
=3D20
paper manufacturing plant and proved to be suitable. However, high-quali=
=3D
ty=3D20
feldspar, silica and bentonite were not available locally, so it was nece=
=3D
ssary to=3D20
turn to commercially produced materials for the rest of the recipe.=3D20=3D=
20=3D
Therefore after a series of tests involving slight alterations in the maj=
=3D
or body=3D20
constituents of kaolin, feldspar and silica with the addition, or deletio=
=3D
n, of=3D20
auxiliary fluxes, the following recipe seemed the most favourable:
50% Tonganah kaolin
30% potash feldspar
20% silica 300
5% bentonite H
(For further information on this research refer to Ceramics Technical, No=
=3D
.1,=3D20
1995, and Ceramic Arts and Perception, Vol.24, 1996.)
Personally, I feel you should contact max.clay(at)clayworksaustralia.com =
=3D
(just=3D20
substitute @ for (at)). Max is a very knowledgeable guy and as the=3D20
manufacturer he would be more than willing to help you with your concerns=
=3D
.
Regards
Johanna
Johanna DeMaine
http://johanna.demaine.org
http://overglaze.info
http://allthatissublime.com
Clay art on sat 9 jun 12
Johanna, thank you for this information. I did ask Max this very same
question some time back and never got an answer. It is possible that he did
not get my e-mail. Maybe I should contact him again., since I could not get
any clear answer on this yet.
It is interesting that you mention that the clay was formulated to be used
without glaze. That is how I keep my exterior. The very first time that I
used the clay, the final outcome gave me a smooth somewhat shiny sheen on
the unglazed areas. After that I had to polish the pots with a diamond pad
to get it smooth. At first I thought it had something to do with the firing
and new elements, but I changed my elements at least once since 2005 when I
started working with this clay body, but never did I get that smooth surfac=
e
again. I wonder if they changed the recipe from those days. I am still
working with clay from before they had problems in the mines.
The other problem with the tiny ridges that I experience , also developed
later on, but in this instance I cannot say if it is me changing my methods
to get an easier way to work, or if the problem developed in the clay. That
being said, if I call it a "problem", I have to qualify that the clay is
what it is. In any other instance it works well for me. It is just that I
use it in a specific manner and would like to see if I can eliminate the
tiny lines like one would do with slip casting. Always aiming for the
better............
Antoinette Badenhorst
www.porcelainbyAntoinette.com
-----Original Message-----
From: Johanna Demaine [mailto:johanna@DEMAINE.ORG]
Sent: Friday, June 08, 2012 8:10 PM
To: Clayart@LSV.CERAMICS.ORG; clayart.friends@GMAIL.COM
Cc: Johanna Demaine
Subject: Re: A question for porcelain scientists among us.
Hi Antoinette
Just to put the record straight, the following is an extract from "Porcelai=
n
and Bone China" by Sasha Wardell.
"Les Blakebrough (Australia) has produced a produced a porcelain clay with
particularly white, translucent qualities. Southern Ice Porcelain derives
its name from the area it was generated-Hobart, Tasmania, which is one of
the southernmost parts of the Southern Hemisphere. It was developed over a
period of six years by a small team of associates with the support of the
Australian Research Council and the University of Tasmania. Since the
commercial release by Clayworks of Dandenong, Victoria, the clay is now
being exported to several countries including th UK and USA.
One of the issues that drove this research was the fact that Blakebrough
wanted a clay that would stand up to scrutiny even if it remained unglazed.
Being dissatisfied with what was currently available, he embarked on the
Southern Ice Project, attempting to use the local raw materials. Kaolin
deposits found at Tonganah, near Scottsdale, were already being used in a
paper manufacturing plant and proved to be suitable. However, high-quality
feldspar, silica and bentonite were not available locally, so it was
necessary to turn to commercially produced materials for the rest of the
recipe.
Therefore after a series of tests involving slight alterations in the major
body constituents of kaolin, feldspar and silica with the addition, or
deletion, of auxiliary fluxes, the following recipe seemed the most
favourable:
50% Tonganah kaolin
30% potash feldspar
20% silica 300
5% bentonite H
(For further information on this research refer to Ceramics Technical, No.1=
,
1995, and Ceramic Arts and Perception, Vol.24, 1996.)
Personally, I feel you should contact max.clay(at)clayworksaustralia.com
(just substitute @ for (at)). Max is a very knowledgeable guy and as the
manufacturer he would be more than willing to help you with your concerns.
Regards
Johanna
Johanna DeMaine
http://johanna.demaine.org
http://overglaze.info
http://allthatissublime.com
Joel Browne on sun 10 jun 12
Hello Fred. Sorry for this late reply, this is cause I hoped to catch up
again with the people I know at the mine, and I have!
About Southern Ice, I was told that this was looked at a few years ago by=
=3D
the company (who are part of a much larger international company) and the=
=3D
opinion was it was =3D93unremarkable=3D94 and their customers (who are main=
ly=3D
in
Asia) are making better. I do not have more details as thought asking may=
=3D
be
difficult (confidentiality with their customers) and Im not too
concerned/interested as I work in stoneware.
About halloysite, I was told it is found in other places but that in New
Zealand is the only mine in operation, and the others are mixed with othe=
=3D
r
minerals or is dirty. There was meant to be a mine somewhere in the US, b=
=3D
ut
this stopped operating years back, and despite some big claims of it
starting again this has not happened.
Oh, and I hope you did not think I was criticising when I corrected the
spelling of halloysite.
Interesting, but it doesn=3D92t get pots made!
Clay art on sun 10 jun 12
Don't think so Jackie. I fire electric and that is exactly my point and I
know others have the same problem. I can tell you this though: the more yo=
u
compact as you go, the lesser unevenness in the end and I am suddenly
wondering if I am answering my own question while I am answering you.
Let me explain: I normally throw very slowly; what I mean by that, is that
my finger touches every surface of the wall as I pushes it upward. ( Note
that I push, not pull the walls) In that way, I start compacting my clay
from the moment after I start lifting the clay. Every once in a while, when
I am under pressure, I end up with wheel rings that does not show on the
bisque, but only shows after the final firing. Even when I realize that I
went too fast when I throw, compacting afterwards does NOT eliminate those
rings.
I have a similar theory about teapot spouts that unwind in the final firing=
:
I could never understand why others have such a problem, while I never have
to pay attention to that at all, until one day that I was hurriedly
throwing spouts way too fast and ended up with a crooked spout. From that
day on I focused on throwing slower and touching and compacting every part
of the wall from the moment I start lifting the walls. Never had unwinding
spouts again.
Now, back to my own problem: I just now realized that I attach the fresh
clay strips and then let it sit to dry off a little bit to make it easier t=
o
smooth it out. I don't know if you know that you can rewet porcelain walls
after it already started to dry off and reshape it (only up to a certain
point of dryness, or else you will run into delamination of the clay walls)=
.
I wet the walls. That softens the clay considerably, especially as I work
with thin walls. So when I attach a fresh strip I normally let it sit , to
prevent too much deformation during handling and then smooth it later. I
think I am going to see if I can find a different way to do that. Hmmmmm, I
wonder if I am onto a solution...............always have to deal with the
porcelain diva and her ways!
BTW. I will be teaching 3 workshops from July to November in different part=
s
of the country, demonstrating my porcelain ways. July I will teach at Oakto=
n
Community College in Chicago. November I will be teaching at John Campbell
Folk School in North Carolina. That is a hands-on workshop. Details about
the other workshop will be announced a little later. Hope to see some of
you at one of these workshops.
Best wishes.
Antoinette Badenhorst
www.porcelainbyAntoinette.com
-----Original Message-----
From: Jackie.Miller.Clay [mailto:jackie.miller.clay@gmail.com]
Sent: Sunday, June 10, 2012 11:19 AM
To: Clay art
Cc: Clayart@LSV.CERAMICS.ORG
Subject: Re: A question for porcelain scientists among us.
I have found that I can get a really lovely soft smooth surface at bisque,
but it will be a bit rougher when fired up to 10 in reduction. I have
wondered if it would stay smoother if fired in oxidation.
Jackie
Jacqueline Miller
On Jun 9, 2012, at 2:19 PM, Clay art wrote:
> Johanna, thank you for this information. I did ask Max this very same
> question some time back and never got an answer. It is possible that
> he did not get my e-mail. Maybe I should contact him again., since I
> could not get any clear answer on this yet.
>
> It is interesting that you mention that the clay was formulated to be
> used without glaze. That is how I keep my exterior. The very first
> time that I used the clay, the final outcome gave me a smooth somewhat
> shiny sheen on the unglazed areas. After that I had to polish the pots
> with a diamond pad to get it smooth. At first I thought it had
> something to do with the firing and new elements, but I changed my
> elements at least once since 2005 when I started working with this
> clay body, but never did I get that smooth surface again. I wonder if
> they changed the recipe from those days. I am still working with clay fro=
m
before they had problems in the mines.
>
> The other problem with the tiny ridges that I experience , also
> developed later on, but in this instance I cannot say if it is me
> changing my methods to get an easier way to work, or if the problem
> developed in the clay. That being said, if I call it a "problem", I
> have to qualify that the clay is what it is. In any other instance it
> works well for me. It is just that I use it in a specific manner and
> would like to see if I can eliminate the tiny lines like one would do
> with slip casting. Always aiming for the better............
> Antoinette Badenhorst
> www.porcelainbyAntoinette.com
>
> -----Original Message-----
> From: Johanna Demaine [mailto:johanna@DEMAINE.ORG]
> Sent: Friday, June 08, 2012 8:10 PM
> To: Clayart@LSV.CERAMICS.ORG; clayart.friends@GMAIL.COM
> Cc: Johanna Demaine
> Subject: Re: A question for porcelain scientists among us.
>
> Hi Antoinette
> Just to put the record straight, the following is an extract from
> "Porcelain and Bone China" by Sasha Wardell.
>
> "Les Blakebrough (Australia) has produced a produced a porcelain clay
> with particularly white, translucent qualities. Southern Ice Porcelain
> derives its name from the area it was generated-Hobart, Tasmania,
> which is one of the southernmost parts of the Southern Hemisphere. It
> was developed over a period of six years by a small team of associates
> with the support of the Australian Research Council and the University
> of Tasmania. Since the commercial release by Clayworks of Dandenong,
> Victoria, the clay is now being exported to several countries including t=
h
UK and USA.
>
> One of the issues that drove this research was the fact that
> Blakebrough wanted a clay that would stand up to scrutiny even if it
remained unglazed.
>
> Being dissatisfied with what was currently available, he embarked on
> the Southern Ice Project, attempting to use the local raw materials.
> Kaolin deposits found at Tonganah, near Scottsdale, were already being
> used in a paper manufacturing plant and proved to be suitable.
> However, high-quality feldspar, silica and bentonite were not
> available locally, so it was necessary to turn to commercially
> produced materials for the rest of the recipe.
>
> Therefore after a series of tests involving slight alterations in the
> major body constituents of kaolin, feldspar and silica with the
> addition, or deletion, of auxiliary fluxes, the following recipe
> seemed the most
> favourable:
>
> 50% Tonganah kaolin
> 30% potash feldspar
> 20% silica 300
> 5% bentonite H
>
> (For further information on this research refer to Ceramics Technical,
> No.1, 1995, and Ceramic Arts and Perception, Vol.24, 1996.)
>
> Personally, I feel you should contact
> max.clay(at)clayworksaustralia.com
> (just substitute @ for (at)). Max is a very knowledgeable guy and as
> the manufacturer he would be more than willing to help you with your
concerns.
>
> Regards
> Johanna
>
> Johanna DeMaine
> http://johanna.demaine.org
> http://overglaze.info
> http://allthatissublime.com
Jackie.Miller.Clay on sun 10 jun 12
I have found that I can get a really lovely soft smooth surface at bisque, =
b=3D
ut it will be a bit rougher when fired up to 10 in reduction. I have wonder=
e=3D
d if it would stay smoother if fired in oxidation.
Jackie
Jacqueline Miller
On Jun 9, 2012, at 2:19 PM, Clay art wrote:
> Johanna, thank you for this information. I did ask Max this very same
> question some time back and never got an answer. It is possible that he d=
i=3D
d
> not get my e-mail. Maybe I should contact him again., since I could not g=
e=3D
t
> any clear answer on this yet.
>=3D20
> It is interesting that you mention that the clay was formulated to be use=
d=3D
> without glaze. That is how I keep my exterior. The very first time that I
> used the clay, the final outcome gave me a smooth somewhat shiny sheen on
> the unglazed areas. After that I had to polish the pots with a diamond pa=
d=3D
> to get it smooth. At first I thought it had something to do with the firi=
n=3D
g
> and new elements, but I changed my elements at least once since 2005 when=
I=3D
> started working with this clay body, but never did I get that smooth surf=
a=3D
ce
> again. I wonder if they changed the recipe from those days. I am still
> working with clay from before they had problems in the mines.
>=3D20
> The other problem with the tiny ridges that I experience , also developed
> later on, but in this instance I cannot say if it is me changing my metho=
d=3D
s
> to get an easier way to work, or if the problem developed in the clay. Th=
a=3D
t
> being said, if I call it a "problem", I have to qualify that the clay is
> what it is. In any other instance it works well for me. It is just that I
> use it in a specific manner and would like to see if I can eliminate the
> tiny lines like one would do with slip casting. Always aiming for the
> better............
> Antoinette Badenhorst
> www.porcelainbyAntoinette.com
>=3D20
> -----Original Message-----
> From: Johanna Demaine [mailto:johanna@DEMAINE.ORG]
> Sent: Friday, June 08, 2012 8:10 PM
> To: Clayart@LSV.CERAMICS.ORG; clayart.friends@GMAIL.COM
> Cc: Johanna Demaine
> Subject: Re: A question for porcelain scientists among us.
>=3D20
> Hi Antoinette
> Just to put the record straight, the following is an extract from "Porcel=
a=3D
in
> and Bone China" by Sasha Wardell.
>=3D20
> "Les Blakebrough (Australia) has produced a produced a porcelain clay wit=
h=3D
> particularly white, translucent qualities. Southern Ice Porcelain derives
> its name from the area it was generated-Hobart, Tasmania, which is one of
> the southernmost parts of the Southern Hemisphere. It was developed over=
a=3D
> period of six years by a small team of associates with the support of the
> Australian Research Council and the University of Tasmania. Since the
> commercial release by Clayworks of Dandenong, Victoria, the clay is now
> being exported to several countries including th UK and USA.
>=3D20
> One of the issues that drove this research was the fact that Blakebrough
> wanted a clay that would stand up to scrutiny even if it remained unglaze=
d=3D
.
>=3D20
> Being dissatisfied with what was currently available, he embarked on the
> Southern Ice Project, attempting to use the local raw materials. Kaolin
> deposits found at Tonganah, near Scottsdale, were already being used in a
> paper manufacturing plant and proved to be suitable. However, high-quali=
t=3D
y
> feldspar, silica and bentonite were not available locally, so it was
> necessary to turn to commercially produced materials for the rest of the
> recipe.
>=3D20
> Therefore after a series of tests involving slight alterations in the maj=
o=3D
r
> body constituents of kaolin, feldspar and silica with the addition, or
> deletion, of auxiliary fluxes, the following recipe seemed the most
> favourable:
>=3D20
> 50% Tonganah kaolin
> 30% potash feldspar
> 20% silica 300
> 5% bentonite H
>=3D20
> (For further information on this research refer to Ceramics Technical, No=
.=3D
1,
> 1995, and Ceramic Arts and Perception, Vol.24, 1996.)
>=3D20
> Personally, I feel you should contact max.clay(at)clayworksaustralia.com
> (just substitute @ for (at)). Max is a very knowledgeable guy and as the
> manufacturer he would be more than willing to help you with your concerns=
.=3D
>=3D20
> Regards
> Johanna
>=3D20
> Johanna DeMaine
> http://johanna.demaine.org
> http://overglaze.info
> http://allthatissublime.com
Snail Scott on mon 11 jun 12
On Jun 10, 2012, at 11:18 AM, Jackie.Miller.Clay wrote:
> I have found that I can get a really lovely soft smooth surface at =3D
bisque, but it will be a bit rougher when fired up to 10 in reduction. I =
=3D
have wondered if it would stay smoother if fired in oxidation...
It ain't the reduction, it's the vitrification, and that=3D20
will be the same regardless of the atmosphere.=3D20
In the typical low-temp bisque firing, the particles=3D20
of clay are just melted enough to fuse together=3D20
and hold, but not melted enough to shift their=3D20
positions relative to one another. (You may be=3D20
aware that there is almost no shrinkage at these=3D20
low temps, either.) When you fire to vitrification,=3D20
the clay particles are actually melting and shifting,=3D20
and the smooth alignment they had when dry (or=3D20
low-bisqued) will not be retained. This is more=3D20
pronounced with clay bodies containing grog or=3D20
sand, as the clay tightens up around those=3D20
non-shrinking solid chunks.
-Snail
Jackie.Miller.Clay on tue 12 jun 12
I recall when I was in school testing various clays that we made in both ox=
i=3D
dation and reduction, that the reduction firing always seemed to produce a =
r=3D
ougher clay. Grog or other inclusions seemed more likely to pop from the su=
r=3D
face in reduction as well. The oxidation and reduction firings were both at=
t=3D
he same temps. I always wondered why there was this difference.
Jackie
On Jun 11, 2012, at 10:03 AM, Snail Scott wrote=
:=3D
> On Jun 10, 2012, at 11:18 AM, Jackie.Miller.Clay wrote:
>> I have found that I can get a really lovely soft smooth surface at bisqu=
e=3D
, but it will be a bit rougher when fired up to 10 in reduction. I have won=
d=3D
ered if it would stay smoother if fired in oxidation...
>=3D20
> It ain't the reduction, it's the vitrification, and that=3D20
> will be the same regardless of the atmosphere.=3D20
>=3D20
> In the typical low-temp bisque firing, the particles=3D20
> of clay are just melted enough to fuse together=3D20
> and hold, but not melted enough to shift their=3D20
> positions relative to one another. (You may be=3D20
> aware that there is almost no shrinkage at these=3D20
> low temps, either.) When you fire to vitrification,=3D20
> the clay particles are actually melting and shifting,=3D20
> and the smooth alignment they had when dry (or=3D20
> low-bisqued) will not be retained. This is more=3D20
> pronounced with clay bodies containing grog or=3D20
> sand, as the clay tightens up around those=3D20
> non-shrinking solid chunks.
>=3D20
> -Snail
Snail Scott on wed 13 jun 12
On Jun 12, 2012, at 7:03 AM, Jackie.Miller.Clay wrote:
> I recall when I was in school testing various clays that we made in =3D
both oxidation and reduction, that the reduction firing always seemed to =
=3D
produce a rougher clay. Grog or other inclusions seemed more likely to =3D
pop from the surface in reduction as well. The oxidation and reduction =3D
firings were both at the same temps. I always wondered why there was =3D
this difference...
If there was any iron in the clay, it would have increased=3D20
the vitrification of that clay when fired in reduction. Same=3D20
clay, but more vitrified (and thus grittier surfaces) than the=3D20
same clay fired at the same temp in oxidation. Same
temperature (or cone) does not equal same vitrification if=3D20
the atmosphere is different.
-Snail
ivor and olive lewis on wed 13 jun 12
To amplify Snails comments.
Kingery, Bowen and Uhlmann in their compressive text "Introduction to
Ceramics" describe the processes which bring a ceramic to maturity.
Chapter ten, "Grain Growth Sintering and Vitrification" covers things in
some detail.including "Recrystalisation" and "Grain Growth". The problems
Antoinette is facing probably originate in these processes.
One conclusion that seems important. As temperature increases large
fragments of raw materials grow larger at the expense of smaller particles
which can be eliminated.
Regards,
Ivor Lewis,
REDHILL,
South Australia
Jackie Miller on wed 13 jun 12
Thanks
Sent from my iPhone
On Jun 13, 2012, at 8:55 AM, Snail Scott wrote:
> On Jun 12, 2012, at 7:03 AM, Jackie.Miller.Clay wrote:
>> I recall when I was in school testing various clays that we made in both=
o=3D
xidation and reduction, that the reduction firing always seemed to produce =
a=3D
rougher clay. Grog or other inclusions seemed more likely to pop from the =
s=3D
urface in reduction as well. The oxidation and reduction firings were both =
a=3D
t the same temps. I always wondered why there was this difference...
>=3D20
>=3D20
> If there was any iron in the clay, it would have increased=3D20
> the vitrification of that clay when fired in reduction. Same=3D20
> clay, but more vitrified (and thus grittier surfaces) than the=3D20
> same clay fired at the same temp in oxidation. Same
> temperature (or cone) does not equal same vitrification if=3D20
> the atmosphere is different.
>=3D20
> -Snail
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