Ron Roy on thu 10 jun 10
Hi Ed,
I have never seen any cristobalite at 1100C either - where is he
getting his information from.
Where ever it is it is clearly wrong. As I said - I can provide charts
of cone 10 dark bodies with lots of cristobalite in them. Just let me
know where to send copies to.
I know you did not have any of your dark clays measured or you would
have seen what I am talking about.
I will measure some samples for you - they are easy to make and it
will ony cost you the postage to send them.
RR
Quoting Edouard Bastarache :
> Ron,
>
> Smart.Conseil graduated in industrial ceramic technology,
> trained to work for the industry at the Verzion school.
> Those guys work for Sevres, Limoges, Gien, etc.
>
> http://www.gien.com/
>
> What I say was explained to me by him when we had an argument on Clayart =
on
> this issue, a few hears ago.
> At the Gien factory he does not high-fire nor does he uses dark burning
> clays; but they own whatever laboratory tools you may think of.
> He fires at about 2000-2100 F if I recall correctly.
> A set of their dishes costs 3,000-5,000 dollars,
> so he can not fool around.
> Years ago, to fool around with raw materials, I tested about
> 220-240 C/9-10 brown redux clays of whom about 75 were
> without spar, and I did not encounter any problem.
> So, that is the way he explained these flawless/sparless
> dark high-fire redux clays...
>
> Gis,
>
> Edouard Bastarache
> Spertesperantisto
>
> Sorel-Tracy
> Quebec
>
> http://www.flickr.com/photos/30058682@N00/
> http://edouardbastarache.blogspot.com/
> http://blogsalbertbastarache.blogspot.com/
> http://cerampeintures.blogspot.com/
> http://perso.wanadoo.fr/smart2000/index.htm
>
>
>
>
>
>
> ----- Original Message -----
> From: "Ron Roy"
> To:
> Sent: Thursday, June 10, 2010 12:34 PM
> Subject: Re: Adding sand and/or sandstone to clay body
>
>
>> Hi Ed,
>>
>> I have lots of dilatometer charts showing all kinds of cristobalite in
>> high iron bodies - in fact I have read that iron even helps the
>> cristobalite to form.
>>
>> What does Smart base his findings on - any diatometry or is it theory?
>> What temperature does he say this happens?
>>
>> RR
>>
>>
>>
>> Quoting Edouard Bastarache :
>>
>>> Eric,
>>>
>>>
>>> The Fe2O3, in reduction firing, will become FeO, a very powerful flux a=
nd
>>> at
>>> high temp, will prevent the formation of cristobalite by
>>> producing "Fayalite" in reacting with silica.
>>> I have sent a few posts on this matter to Clayart, backed by the
>>> knowledge
>>> of Smart.Conseil.
>>> Do not forget to fire in reduction if KNaO is not present,,,
>>>
>>> Gis,
>>>
>>> Edouard Bastarache
>>> Spertesperantisto
>>>
>>> Sorel-Tracy
>>> Quebec
>>>
>>> http://www.flickr.com/photos/30058682@N00/
>>> http://edouardbastarache.blogspot.com/
>>> http://blogsalbertbastarache.blogspot.com/
>>> http://cerampeintures.blogspot.com/
>>> http://perso.wanadoo.fr/smart2000/index.htm
>>>
>>
>
Edouard Bastarache on thu 10 jun 10
Ron,
Smart.Conseil graduated in industrial ceramic technology,
trained to work for the industry at the Verzion school.
Those guys work for Sevres, Limoges, Gien, etc.
http://www.gien.com/
What I say was explained to me by him when we had an argument on Clayart on
this issue, a few hears ago.
At the Gien factory he does not high-fire nor does he uses dark burning
clays; but they own whatever laboratory tools you may think of.
He fires at about 2000-2100 F if I recall correctly.
A set of their dishes costs 3,000-5,000 dollars,
so he can not fool around.
Years ago, to fool around with raw materials, I tested about
220-240 C/9-10 brown redux clays of whom about 75 were
without spar, and I did not encounter any problem.
So, that is the way he explained these flawless/sparless
dark high-fire redux clays...
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://blogsalbertbastarache.blogspot.com/
http://cerampeintures.blogspot.com/
http://perso.wanadoo.fr/smart2000/index.htm
----- Original Message -----
From: "Ron Roy"
To:
Sent: Thursday, June 10, 2010 12:34 PM
Subject: Re: Adding sand and/or sandstone to clay body
> Hi Ed,
>
> I have lots of dilatometer charts showing all kinds of cristobalite in
> high iron bodies - in fact I have read that iron even helps the
> cristobalite to form.
>
> What does Smart base his findings on - any diatometry or is it theory?
> What temperature does he say this happens?
>
> RR
>
>
>
> Quoting Edouard Bastarache :
>
>> Eric,
>>
>>
>> The Fe2O3, in reduction firing, will become FeO, a very powerful flux an=
d
>> at
>> high temp, will prevent the formation of cristobalite by
>> producing "Fayalite" in reacting with silica.
>> I have sent a few posts on this matter to Clayart, backed by the
>> knowledge
>> of Smart.Conseil.
>> Do not forget to fire in reduction if KNaO is not present,,,
>>
>> Gis,
>>
>> Edouard Bastarache
>> Spertesperantisto
>>
>> Sorel-Tracy
>> Quebec
>>
>> http://www.flickr.com/photos/30058682@N00/
>> http://edouardbastarache.blogspot.com/
>> http://blogsalbertbastarache.blogspot.com/
>> http://cerampeintures.blogspot.com/
>> http://perso.wanadoo.fr/smart2000/index.htm
>>
>
Neon-Cat on sat 12 jun 10
Ron, please discuss the limits of your testing process and its
technology and the limits of your particular older model dilatometer
and how you address these limits. Many of us have been most curious
(and no, I am not going to buy a $30.00 article so please don=3DE2=3D80=3D9=
9t
suggest that again =3DE2=3D80=3D93 it will not help me understand the basis=
of yo=3D
ur
claims for what you can do with your dilatometer). Dilatometery is not
routinely used when researchers study clay bodies and certainly never
alone. =3DE2=3D80=3D9CEasy=3DE2=3D80=3D9D and inexpensive does not necessar=
ily lead to =3D
valid
results that can be put into practical use by studio potters and clay
workers. If dilatometery were an easy and reliable method of
ascertaining the identity of clay body components scientists around
the world would rejoice and take up its practice. That they have not
and never did is telling.
Ron, please tell us and or provide:
1. The make, age, and model number of your contact pushrod
dilatometer. Is it a single or double push-rod dilatometer? Is its
sample holder geometry vertical or horizontal?
2. What is the heating rate (C/min) you use when testing for cristobalite?
3. What is the temperature range used during testing proceedures?
4. What is the sample preparation method and sample specifications?
5. Are you sent a fired or unfired specimen?
6. What is the sensitivity of your sensor, its precision and accuracy?
7. What is the frequency and means of calibration?.
8. Is your dilatometer computer assisted beyond factory specifications
and if so what enhancements have you added?
9. What value for thermal diffusivity do you assign for clay body samples?
10. Do you consider anisotropy when testing for crystalline phase changes?
11. You never mention tridymite. Why?
12. Do you consider the elastic properties of our composite ceramic
materials when preparing clay body advisories for potters?
13. Is micro-cracking in a sample an issue?
14. How do you deal with interferences (vibratory, electromagnetic,
ferro - to paramagnetic influences contributed by iron species,
humidity, sample-clasping in push-rod machines, left-over reactants in
the body, etc.)?
15. Is the chart of heating and cooling or just heating?
16. Can you or someone provide a link to a photo of one of your typical cha=
=3D
rts?
17. Will you description just what on a chart =3DE2=3D80=3D9Cconfirms=3DE2=
=3D80=3D9D cr=3D
istobalite for you?
18. You speak of some clays having a =3DE2=3D80=3D9Clot=3DE2=3D80=3D9D of c=
ristobalite.=3D
What
special calibration techniques do you use to determine concentration
once you think you have found cristobalite?
19. How do you deal with the small irreversible temperature variations
related to chemical impurities that may have been introduced anywhere
along the line of making that will affect your dilatometer readings?
20. What, if any, suitable calibration methods do you use to identify
phases present?
The limitations of dilatometery (alternate spelling, dilatometry)
especially single contact-pushrod older model units that are not very
sensitive, anisotropy, and hysteresis inherent in dilatometric
testing, are enough (I could go on but won=3DE2=3D80=3D99t now) to preclude=
your
claims of identifying cristobalite in a sample whose fired composition
you don=3DE2=3D80=3D99t know or understand. Damping microgaps between the
cristobalite particles and the matrix after heat treatment or between
any type of particles is also a problem in dilatometric
interpretation.
There are a variety of physical phenomena for each clay body that
result in dimensional change (melting, glass formation, secondary
transitions, crystallization, devitrification, physical aging of the
sample, etc.). The change in length of a fired clay body is related to
the change in temperature created and the original length by a
constant that depends on the material, in the case of a clay body =3DE2=3D8=
0=3D93=3D
a
composite body, not its assumed individual components. The same can be
said for volume expansion (usually about three times the coefficient
of thermal linear expansion) =3DE2=3D80=3D93 it is the volume change for a =
compos=3D
ite
body that is read, not individual quartz (cristobalite inversions are
not generally spoken of in relation to dilatometery). Phase
transformations are common in ceramic materials and are accompanied by
sharp changes in specific volume and thermal properties. There can be
two or three (or more) thermodynamically favored domain structures
that exist in the vicinity of a known phase transition. Around this
transition temperature of restructuring one phase may be expanding,
another contracting, simultaneously or at slightly different
temperatures. Then what? Dilatometers can locate the alpha-beta quartz
transition that is now know to go through two intermediaries (the full
=3DCE=3DB1-=3DCE=3DB2 transition upon cooling is beta-Qz --> 1Qz inc --> 3Q=
z inc --=3D
>
alpha-Qz) but make no claims to do so for cristobalite and for good
reason =3DE2=3D80=3D93 cristobalite (now with an a=3DE2=3D80=3D99 phase) ha=
s been recor=3D
ded to
experience inversion from 120 =3DE2=3D80=3D93 272 C (248 =3DE2=3D80=3D93 52=
1.6 F) and t=3D
o form
mixed phases with tridymite, another form of silica (with numerous
distinct forms) that also inverts over a long range at these lower
temperatures. Both quartz and cristobalite may be substituted by
contaminants that change their inversion points. The shortsightedness
of your entire approach and the bold, consistent, constant portrayal
of cristobalite as a major =3DE2=3D80=3D9Cenemy=3DE2=3D80=3D9D are just unc=
onscionable.
How many perfectly fine clay bodies have been junked at your say-so?
All this disparaging on your part of clay bodies containing iron,
silica-sand, talc, illite, and some brands of raw commercial clay, or
competitor=3DE2=3D80=3D99s commercial clay bodies leaves me somewhere betwe=
en mad
and sad. What will remain of the beauties, wonder, and time-honored
fundamental materials of our craft by the time you are through making
so many of them off-limits?
Here=3DE2=3D80=3D99s to eyes wide open...on such an important topic and one=
put
forth by an influential man of our time, potters and clay workers
deserve to understand the truth of this matter in some detail. We
should also wonder if we are providing straightforward and correct
answers to the next generation of studio potters.
Thank you.
Marian
Neon-Cat
www.neon-cat.com
Neon-Cat on sat 12 jun 10
I am continually dumbfounded, Ron, that you claim to be able to
identify, =3DE2=3D80=3D9Csee=3DE2=3D80=3D9D, =3DE2=3D80=3D9Cfind=3DE2=3D80=
=3D9D, and =3DE2=3D80=3D9Cconfi=3D
rm=3DE2=3D80=3D9D the presence or absence of
cristobalite in clay bodies. A dilatometer was never meant to be used
to identify the chemical or mineral constituents in a clay body (or
anything). In the countless articles I=3DE2=3D80=3D99ve read no one but you=
makes
such exaggerated claims and inferences. A dilatometric reading
(=3DE2=3D80=3D9Cchart=3DE2=3D80=3D9D or =3DE2=3D80=3D9Ccurve=3DE2=3D80=3D9D=
as you call it) records=3D
the thermal expansion (a
mechanical and/or physical property) that can then provide the
determination of the coefficient of linear expansion that is useful
for calculating thermal stress factors in the composite clay body. It
can only help an operator make an indirect assessment of the phase
composition at a particular time within the composite material under
investigation. In my world what you are doing is providing an
=3DE2=3D80=3D98educated guess=3DE2=3D80=3D99 or =3DE2=3D80=3D98best guessti=
mate=3DE2=3D80=3D99. A d=3D
ilatometer is not a
stand-alone tool for determining the specific chemical or mineralogy
of a single component in a composite clay body. And reporting is valid
only for the temperature and time and atmosphere at which a sample was
fired. Your approach and claims to be able to identify cristobalite
using dilatometery reminds me very much of the tee-hee games young
adults played when looking at a guy=3DE2=3D80=3D99s shoe size and then imag=
ining
that the male under scrutiny must therefore have other enhanced
physical attributes if he had long feet.
You =3DE2=3D80=3D9Csee=3DE2=3D80=3D9D cristobalite everywhere, Ron. By now =
I=3DE2=3D80=3D99ve=3D
probably read at
least a thousand peer-reviewed journal articles on fired clay bodies
and I am finding so very little or any cristobalite at all reported to
be formed in mid to high-fired clay bodies of all types (and these
include red iron-bearing clays, illite-containing clays, talc bodies,
fine and large particle-sized silica or sand containing clays, etc.)
that have had a proper analysis. If dilatometery were an easy and
reliable method of ascertaining the identity of clay body components
scientists around the world would rejoice and take up its practice.
That they have not and never did is telling. If you have an answer to
how it is you do what no one (from peer-reviewed research scientists
to industrial manufacturers large and small), would dream of doing,
please let us all know.
If you do not know what is being formed when we fire a clay body I am
at a loss to understand how you can condemn, for example, Red Art
clay. Red Art is an illite-containing clay. Illite when fired will
form potassium aluminum silicates and/or potassium feldspars. This is
good for us as potters, not bad. Yet you write the use of Red Art
=3DE2=3D80=3D9Cwould be the quickest way to build cristobalite into your fi=
nished
product=3DE2=3D80=3D9D. Really? How so?
When the topic comes up you never step up to the plate to tell us
about iron chemistry as pertains to iron in its many forms or the iron
reactions that occur when, for example, iron oxide is heated or cooled
in our different kiln atmospheres. You say only that iron is
=3DE2=3D80=3D9Ccomplicated=3DE2=3D80=3D9D while going on to condemn its use=
because you=3D
think that
it is prone to enhancing cristobalite formation because your charts
are =3DE2=3D80=3D9Cshowing=3DE2=3D80=3D9D you =3DE2=3D80=3D9Call kinds of c=
ristobalite in hig=3D
h iron bodies=3DE2=3D80=3D9D.
Iron and silica form many important fired clay body =3DE2=3D80=3D9Cmineral
assemblages=3DE2=3D80=3D9D (fayalite is just one possibility; it all depend=
s on t=3D
he
system =3DE2=3D80=3D93 what we put into the clay body and how we fire it).
To write that someone needs at least 10% spar to prevent the
cristobalite you are =3DE2=3D80=3D9Cseeing=3DE2=3D80=3D9D is irresponsible.=
So is writi=3D
ng =3DE2=3D80=3D9Cits the
sodium and potassium that likes melting silica=3DE2=3D80=3D9D, as if cristo=
balite
can only form where there is free unmelted silica and only feldspar
can act as a flux. Cristobalite can be formed in the glassy portions
of our ceramic matrices so just melting silica is no guarantee against
cristobalite. In some systems aluminum can prevent cristobalite
formation, in others mullite suppresses cristobalite formation, and on
and on with different generalities and observations. Much has been
written about cristobalite in the last few decades. In clay bodies
prepared from indigenous (native) clays or those formulated using
commercially available clays and fluxed by a variety of means I am
just not reading about cristobalite. Glass makers sometimes like
putting cristobalite into their glass and they know just how to do it.
It is all about what we are creating -- the minerals and glass
phase(s) -- at specific temperatures and atmospheres. Silica may
preferentially combine with other ions, minerals and phases instead of
morphing into cristobalite. This seems a far more common occurrence.
All manufacturers of dilatometers give the same standard details of
just what properties can be assessed when the length change versus
temperature (expansion or shrinkage on heating) is investigated:
Thermal expansion;
Coefficient of linear thermal expansion;
Sintering temperature and shrinkage steps;
=3DEF=3D80=3DA0Volumetric expansion;
=3DEF=3D80=3DA0Density change;
=3DEF=3D80=3DA0Glass transition temperature;
=3DEF=3D80=3DA0Dilatometric softening point;
=3DEF=3D80=3DA0Phase transitions
Dilatometric readings (dimensional changes of a sample as it is being
heated) can then be used to help develop firing curves, assist during
the study of clay body vitrification, bolster the evaluation of
thermal stress factors, locate quartz inversion, help provide a
semi-quantitative determination of quartz in ceramic bodies
(especially by an evaluation of the volume increase during the
transition of low quartz to high quartz), provide information during
freeze-durability studies, and provide data useful to architects or
engineers determining where to place expansion joints in large ceramic
tile installations. Test methods for measuring thermal expansion with
a dilatometer are given in ASTM C 372. No manufacturer makes a claim
for locating a cristobalite inversion point and certainly they do not
claim that a dilatometer can provide a determination of the presence
and quantity of cristobalite.
Marian
Neon-Cat
www.neon-cat.com
David Finkelnburg on mon 14 jun 10
Marion,
The Orton dilatometer which I have seen Ron use differs from more recent
models only in the output. His outputs mechanically to a pen plotter, more
recent devices typically output a digital file to perform the plot.
ALL dilatometers simply measure change in length per unit length per
degree temperature change both while heating and cooling. The two plots
(heating and cooling) of the length versus temperature curve are
particularly revealing if either shows a significant change in length over =
a
very narrow change in temperature. This is what you get from a crystal
phase change--quartz inversion on cooling being the most common example.
Dilatometry is not terribly high tech. It does require care in sample
preparation and loading in the dilatometer, in selecting the temperature
range to yield useful data without damaging the instrument, and in
interpreting the results.
Good potting,
Dave Finkelnburg
http://www.mattanddavesclays.com
ivor and olive lewis on wed 16 jun 10
During my time in the Physical Metallurgy laboratory using a Chevenard
Differential Dilatometer to determine phase changes in alloy steels I also
measured magnetic properties of those alloys and sent samples to the Micro
Lab where the percentages of alloying fractions were determined. The work I
was doing, using a continuous cooling dilatometry were corroborated by a
colleague who was doing Isothermal Observations using Direct Reading
Dilatometer, with a similar follow through observations.
Whenever possible information obtained from using a dilatometer should be
compared to data from other sources. However, I doubt if those who quarry
and refine ceramic raw materials for sale to the Ceramic Art and Studio
Pottery market make sufficient profit to justify a complex program of
research.
Best regards,
Ivor Lewis,
REDHILL,
South Australia
Ron Roy on wed 23 jun 10
Hi Marian,
My dilatometer was manufactured by Orton - the model is EK - serial #TX 750=
2.
It is a double furnace single horizontal push rod type.
My heating rate is 3C per minute - the rate recommended for calibration.
Temperature range is 0 to 1000C
Samples are cut and ground to 2 inches +or- 0.002.
Samples are sent fired including the cones they are fired with or I
fire my own.
I don't know what you mean by sensitivity of the sensor - that is not
covered in the manual.
I took it to the Orton factory and they calibrated it for me and I
purchased a fused alumina sample and chart to compare with when I
calibrate - about every 50 runs. My calibration charts match the
factory chart.
I only chart the heating curve.
I have no idea what your other questions mean so I can't answer them -
what my machine does is measure the expansion of clay and glaze
samples - a technology that every major manufacturer of glazed ceramic
ware uses to make sure there product does not craze or shiver.
The crystalline phases of silica are clearly seen - as they go through
their inversions - you will instantly see the increase in expansion
expressed in the curve - they are unmistakable - the bigger the
increase the more cristobalite and/or quartz is present.
I'm surprised you have not seen a chart in all your research - there
are some in Mastering Cone 6 Glazes - a whole chapter on the subject
including a set of glazes to help determine the expansion of any
particular clay.
I am just about to renew my subscription to Studio Potter - they sell
back issues - the one with the Sohngen article is still available. The
lead article is on David Shaner and there are 3 on mimbres pottery you
would probably find interesting. The price for members is $25 - if you
send me your mailing address I will buy a copy for you and have it
mailed.
If you want to understand what the cristobalite thing is all about
Sohngen's article is the best way.
I have any number of charts I could scan and send as JPG's - do you
have high speed internet?
I'm sure you will have more questions - I'll try to answer them when I
have the time.
RR
James Freeman on thu 24 jun 10
On Wed, Jun 23, 2010 at 10:15 PM, Ron Roy wrote:
>
> I am just about to renew my subscription to Studio Potter - they sell
> back issues - the one with the Sohngen article is still available. The
> lead article is on David Shaner and there are 3 on mimbres pottery you
> would probably find interesting. The price for members is $25 - if you
> send me your mailing address I will buy a copy for you and have it
> mailed.
>
Wow, Ron! Talk about turning the other cheek! You are a mensch. I
want to be you when I grow up.
While supporting Studio Potter is certainly a good thing, folks may be
unaware that one can request free copies of magazine articles through
inter-library loan. I have a number of such articles in my files, and
even a few that I have shared on the "Resources" page of my website.
They don't send you the whole magazine, just a photocopy or scan of
the article you request. You do not have to return it, and it is all
legal under the fair use strictures of the copyright law (one library
even included a page outlining the ways in which the photocopy could
be used legally).
BTW, that Shaner article, which runs to about 30 pages, is worth the
price of admission by itself.
All the best.
...James
James Freeman
"All I say is by way of discourse, and nothing by way of advice. I
should not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/resources
Eric Hansen on fri 25 jun 10
james: you just earned a gold star in my gmail account!!!!!
On Thu, Jun 24, 2010 at 8:16 AM, James Freeman m
> wrote:
> On Wed, Jun 23, 2010 at 10:15 PM, Ron Roy wrote:
>
> >
> > I am just about to renew my subscription to Studio Potter - they sell
> > back issues - the one with the Sohngen article is still available. The
> > lead article is on David Shaner and there are 3 on mimbres pottery you
> > would probably find interesting. The price for members is $25 - if you
> > send me your mailing address I will buy a copy for you and have it
> > mailed.
> >
>
>
>
> Wow, Ron! Talk about turning the other cheek! You are a mensch. I
> want to be you when I grow up.
>
> While supporting Studio Potter is certainly a good thing, folks may be
> unaware that one can request free copies of magazine articles through
> inter-library loan. I have a number of such articles in my files, and
> even a few that I have shared on the "Resources" page of my website.
> They don't send you the whole magazine, just a photocopy or scan of
> the article you request. You do not have to return it, and it is all
> legal under the fair use strictures of the copyright law (one library
> even included a page outlining the ways in which the photocopy could
> be used legally).
>
> BTW, that Shaner article, which runs to about 30 pages, is worth the
> price of admission by itself.
>
> All the best.
>
> ...James
>
> James Freeman
>
> "All I say is by way of discourse, and nothing by way of advice. I
> should not speak so boldly if it were my due to be believed."
> -Michel de Montaigne
>
> http://www.jamesfreemanstudio.com
> http://www.flickr.com/photos/jamesfreemanstudio/
> http://www.jamesfreemanstudio.com/resources
>
Neon-Cat on sun 18 jul 10
Dear Ron (and others),
I have seen a number of charts and have looked at this issue of you
and your special claims and abilities regarding your dilatometer since
I joined Clayart almost three years ago. I have always been curious as
to the basis of your claims to be able to definitively identify,
qualitatively and quantitatively, either quartz or cristobalite.
The other night I happened upon a book I=3D92d bought a while back but had
not really picked up =3D96 Richard Zakin=3D92s =3D93Ceramics, Ways of Creat=
ion=3D94=3D
.
In it is a nice biographical sketch of you that mentions your
graduation after three years as a special student from Ontario College
of Art in Toronto 1959-1963. Thereafter, some rough times as a potter,
a stint from 1968 =3D96 1983 as a ceramic teacher at Centennial College in
Toronto and the start of the clay supply business Rodaco from
1971-1981, both activities keeping you, to quote the article =3D93(just)
in the black=3D94. Quite a few Clayarters have told me that you are a
chemical engineer. True, not true? I don=3D92t know and don=3D92t care exce=
pt
that it affects how we talk (or not) about your claims for
dilatometery. In spite of what James and others believe I have no
interest in anything but the truth of clay science issues as discussed
on Clayart.
Your claims regarding dilatometery as used by you have always bothered
me but I held off mentioning anything having received some mixed
messages about Clayart as a =3D93family=3D94, =3D93community=3D94, =3D93pub=
=3D94, =3D93fr=3D
iendly
group=3D94, and now but a mere =3D93network=3D94. Don't make waves but do m=
ake
yourself useful seemed to be the message. I did wade into this the
last time around because a couple of people asked me to. I did go all
out to find some precedent for your claims setting aside all personal
irritation at your disparagement of Red Art clay and other materials
as well as all attempts by some pretty darned smart people to present
alternate findings about the products we create in a fired clay body.
And I=3D92m good =3D96 really good at this clay science stuff, spending
countless hours of research following a topic in multi-discipline,
peer reviewed journals from the turn of the last century to within
months of the current date in 2010. Trained and degreed in chemistry,
with a surprising gift and facility for clay science post Lyme
disease, if nothing else I=3D92m thorough, dedicated, persistent, and
tenacious. And, yes, for every post I=3D92ve ever written I have much more
information than was ever posted to Clayart complete with numerous
references. This is my special niche and I am confident =3D96 not arrogant
=3D96 about my abilities. I like knowing how things work and I like studio
art and our world of potters to be somewhat in sync with the modern
world, not laboring and suffering under this cloud of
art-potter-science disconnect. The world is not stupid and in need of
as much =3D93education=3D94 as some of you would have us all thinking. If w=
e
are not making sense even to ourselves much less our ever-increasingly
sophisticated buyers and collectors, how then can we presume to talk
about standards of any sort? If not believable in one area how are we
to be believed in other areas no matter how fancy those newly minted
certificates looks (re: =3D93standards=3D94 thread)?
Anyway, that you can=3D92t answer my questions and have no idea what they
mean (thank goodness I didn=3D92t post the other 18 pages of objections)
shows me that we have no common ground for further conversation. The
questions on the operation and specifications for your dilatometer,
while they point to some of the many problems encountered by those
just trying to follow the linear expansion of materials with a
dilatometer, are really rather moot. Rather we should be able to
discuss the properties of a fired clay body. But you have been
=3D93seeing=3D94 quartz and cristobalite in abundance for so many years tha=
t
it seems hard for you to take an objective look at what is known about
fired clay bodies in 2010. Since the mid-to late 1980=3D92s, first-rate
testing equipment exists so that at every step of the way in a firing
sequence the products formed by us in our kilns can be known with
accuracy. Those that are not keeping up with clay science and
technology are missing some truly remarkable and wonderful things
about this clay-art/functional pottery that we are involved in as a
group.
One of the fundamental occurrences during the firing of a clay body is
the sintering and fusion of our raw materials. We heat to about 1000 C
or so, mindful of temperature lag, and our clay body components start
to fuse. New products form from our initial ingredients. Expansion
rates change from the original. Many materials go through inversion,
not just quartz or cristobalite. The nice thing is that quartz and
cristobalite (forming on the way up as readily as on the way down,
often as an intermediate to tridymite) and any other materials subject
to inversion form a composite, fused, finished fired body. Once taken
into this glorious fusion the linear expansion rate for individual
components declines and inversion becomes physically impossible.
Besides, cristobalite is just a form of silica and can and is used to
form kiln reaction products; it can also exist in its high temperature
form at room temperature. So what is measured in dilatometery is the
firing curve for a composite clay body =3D96 that is what your chart
shows, and is what my last post emphasized. Is there free quartz or
cristobalite? You=3D92ll never know by dilatometery. Interferences
inherent during the entire testing process can be numerous,
complicated, and subject to misinterpretation. All this worry over
your =3D93seeing=3D94 and being able to definitively qualify and quantify
cristobalite is a bit much. I will assume that your zeal has been due
to a genuine, if misguided, desire to be helpful =3D96 an innocent mistake
at the onset regarding what a dilatometer can and cannot do and a
failure to understand the practical limits of the instrument. Anyone
interested in this topic should look first at what a dilatometer is
and what it can do. A good modern understanding of fired clay bodies
is necessary, too. It is not hard and so very, very many of you are
capable if not swayed by the limitations inherent in unreasonable
pseudo-clay science or the posturing of others who claim to be experts
while making you feel that you can=3D92t understand the field in which you
work. Those that I=3D92ve talked with who have not become apathetic find
they can and do understand clay science and have a right good time
doing so.
No, Ron, please don=3D92t send me anything although the Shaner article is
tempting (thanks anyway -- my Jack Troy Shaner book should be along
this week). Within your context I can=3D92t be an advocate for the use of
dilatometery or be persuaded of its legitimacy. I could buy the
article myself but would rather have other more interesting (and
correct) reading materials. The same goes for =3D93Mastering Cone 6
Glazes=3D94 (you once wrote that you liked the way I think and were going
to send me the book).
I put off writing while thoughtfully considering my experiences on
Clayart. I=3D92m going to go on about my business of clay but skip trying
to share further with this list. You all ask that we newcomers be good
and competent and knowledgeable clay workers yet condemn the result.
Frankly, this is attitude is confusingly contradictory. Clay and clay
science are not.
Marian
Neon-Cat
John Goode on mon 19 jul 10
I never saw experience in a text book or wiki pedia?
Too long didnt read?
JBG
On Sun, Jul 18, 2010 at 10:18 PM, Neon-Cat wrote=
=3D
:
> Dear Ron (and others),
>
> I have seen a number of charts and have looked at this issue of you
> and your special claims and abilities regarding your dilatometer since
> I joined Clayart almost three years ago. I have always been curious as
> to the basis of your claims to be able to definitively identify,
> qualitatively and quantitatively, either quartz or cristobalite.
>
> The other night I happened upon a book I=3D92d bought a while back but ha=
d
> not really picked up =3D96 Richard Zakin=3D92s =3D93Ceramics, Ways of Cre=
ation=3D
=3D94.
> In it is a nice biographical sketch of you that mentions your
> graduation after three years as a special student from Ontario College
> of Art in Toronto 1959-1963. Thereafter, some rough times as a potter,
> a stint from 1968 =3D96 1983 as a ceramic teacher at Centennial College i=
n
> Toronto and the start of the clay supply business Rodaco from
> 1971-1981, both activities keeping you, to quote the article =3D93(just)
> in the black=3D94. Quite a few Clayarters have told me that you are a
> chemical engineer. True, not true? I don=3D92t know and don=3D92t care ex=
cept
> that it affects how we talk (or not) about your claims for
> dilatometery. In spite of what James and others believe I have no
> interest in anything but the truth of clay science issues as discussed
> on Clayart.
>
> Your claims regarding dilatometery as used by you have always bothered
> me but I held off mentioning anything having received some mixed
> messages about Clayart as a =3D93family=3D94, =3D93community=3D94, =3D93p=
ub=3D94, =3D93=3D
friendly
> group=3D94, and now but a mere =3D93network=3D94. Don't make waves but do=
make
> yourself useful seemed to be the message. I did wade into this the
> last time around because a couple of people asked me to. I did go all
> out to find some precedent for your claims setting aside all personal
> irritation at your disparagement of Red Art clay and other materials
> as well as all attempts by some pretty darned smart people to present
> alternate findings about the products we create in a fired clay body.
> And I=3D92m good =3D96 really good at this clay science stuff, spending
> countless hours of research following a topic in multi-discipline,
> peer reviewed journals from the turn of the last century to within
> months of the current date in 2010. Trained and degreed in chemistry,
> with a surprising gift and facility for clay science post Lyme
> disease, if nothing else I=3D92m thorough, dedicated, persistent, and
> tenacious. And, yes, for every post I=3D92ve ever written I have much mor=
e
> information than was ever posted to Clayart complete with numerous
> references. This is my special niche and I am confident =3D96 not arrogan=
t
> =3D96 about my abilities. I like knowing how things work and I like studi=
o
> art and our world of potters to be somewhat in sync with the modern
> world, not laboring and suffering under this cloud of
> art-potter-science disconnect. The world is not stupid and in need of
> as much =3D93education=3D94 as some of you would have us all thinking. If=
we
> are not making sense even to ourselves much less our ever-increasingly
> sophisticated buyers and collectors, how then can we presume to talk
> about standards of any sort? If not believable in one area how are we
> to be believed in other areas no matter how fancy those newly minted
> certificates looks (re: =3D93standards=3D94 thread)?
>
> Anyway, that you can=3D92t answer my questions and have no idea what they
> mean (thank goodness I didn=3D92t post the other 18 pages of objections)
> shows me that we have no common ground for further conversation. The
> questions on the operation and specifications for your dilatometer,
> while they point to some of the many problems encountered by those
> just trying to follow the linear expansion of materials with a
> dilatometer, are really rather moot. Rather we should be able to
> discuss the properties of a fired clay body. But you have been
> =3D93seeing=3D94 quartz and cristobalite in abundance for so many years t=
hat
> it seems hard for you to take an objective look at what is known about
> fired clay bodies in 2010. Since the mid-to late 1980=3D92s, first-rate
> testing equipment exists so that at every step of the way in a firing
> sequence the products formed by us in our kilns can be known with
> accuracy. Those that are not keeping up with clay science and
> technology are missing some truly remarkable and wonderful things
> about this clay-art/functional pottery that we are involved in as a
> group.
>
> One of the fundamental occurrences during the firing of a clay body is
> the sintering and fusion of our raw materials. We heat to about 1000 C
> or so, mindful of temperature lag, and our clay body components start
> to fuse. New products form from our initial ingredients. Expansion
> rates change from the original. Many materials go through inversion,
> not just quartz or cristobalite. The nice thing is that quartz and
> cristobalite (forming on the way up as readily as on the way down,
> often as an intermediate to tridymite) and any other materials subject
> to inversion form a composite, fused, finished fired body. Once taken
> into this glorious fusion the linear expansion rate for individual
> components declines and inversion becomes physically impossible.
> Besides, cristobalite is just a form of silica and can and is used to
> form kiln reaction products; it can also exist in its high temperature
> form at room temperature. So what is measured in dilatometery is the
> firing curve for a composite clay body =3D96 that is what your chart
> shows, and is what my last post emphasized. Is there free quartz or
> cristobalite? You=3D92ll never know by dilatometery. Interferences
> inherent during the entire testing process can be numerous,
> complicated, and subject to misinterpretation. All this worry over
> your =3D93seeing=3D94 and being able to definitively qualify and quantify
> cristobalite is a bit much. I will assume that your zeal has been due
> to a genuine, if misguided, desire to be helpful =3D96 an innocent mistak=
e
> at the onset regarding what a dilatometer can and cannot do and a
> failure to understand the practical limits of the instrument. Anyone
> interested in this topic should look first at what a dilatometer is
> and what it can do. A good modern understanding of fired clay bodies
> is necessary, too. It is not hard and so very, very many of you are
> capable if not swayed by the limitations inherent in unreasonable
> pseudo-clay science or the posturing of others who claim to be experts
> while making you feel that you can=3D92t understand the field in which yo=
u
> work. Those that I=3D92ve talked with who have not become apathetic find
> they can and do understand clay science and have a right good time
> doing so.
>
> No, Ron, please don=3D92t send me anything although the Shaner article is
> tempting (thanks anyway -- my Jack Troy Shaner book should be along
> this week). Within your context I can=3D92t be an advocate for the use of
> dilatometery or be persuaded of its legitimacy. I could buy the
> article myself but would rather have other more interesting (and
> correct) reading materials. The same goes for =3D93Mastering Cone 6
> Glazes=3D94 (you once wrote that you liked the way I think and were going
> to send me the book).
>
> I put off writing while thoughtfully considering my experiences on
> Clayart. I=3D92m going to go on about my business of clay but skip trying
> to share further with this list. You all ask that we newcomers be good
> and competent and knowledgeable clay workers yet condemn the result.
> Frankly, this is attitude is confusingly contradictory. Clay and clay
> science are not.
>
> Marian
> Neon-Cat
>
ivor and olive lewis on wed 21 jul 10
Leaving Dilatometry aside, I would ask Marian,
"Was there any experimental evidence in those journals, peer reviewed
articles, and accounts you read that would refute information about the
nature of the polymorphs of Silicon Dioxide and their behaviour during a
potter's firing. Was there anything that would contradict authors of
standard texts whose knowledge we use as instructions for students or for
self improvement ? Do we to discard teachings of Michael Cardew, Cullen
Parmallee, Frank and Janet Hamer, Daniel Rhodes, Emmanuel Cooper and Derek
Royle, Felix and Sonya Singer, David Kingery and his co-authors or Michel
Barsoum ? If there is and if we should, then, as a graduate Chemist with a
Bachelors Degree you owe it to the ceramic arts community in general to
assist in re-educating us to correct our misunderstandings. I'm sure your
opinions would be well received by the editors of currently published
Ceramic Journals".
Best regards,
Ivor Lewis,
REDHILL,
South Australia
Eric Hansen on wed 21 jul 10
Ivor: Well, that is your "who's-who" list. Royle and Barsoum I haven't hear=
d
of, as an aside, if you have bibliographic info on the post to group or to
me direct, as it pleases you.
h a n s e n
On Wed, Jul 21, 2010 at 2:52 AM, ivor and olive lewis u
> wrote:
> Leaving Dilatometry aside, I would ask Marian,
> "Was there any experimental evidence in those journals, peer reviewed
> articles, and accounts you read that would refute information about the
> nature of the polymorphs of Silicon Dioxide and their behaviour during a
> potter's firing. Was there anything that would contradict authors of
> standard texts whose knowledge we use as instructions for students or for
> self improvement ? Do we to discard teachings of Michael Cardew, Cullen
> Parmallee, Frank and Janet Hamer, Daniel Rhodes, Emmanuel Cooper and Dere=
k
> Royle, Felix and Sonya Singer, David Kingery and his co-authors or Michel
> Barsoum ? If there is and if we should, then, as a graduate Chemist with =
a
> Bachelors Degree you owe it to the ceramic arts community in general to
> assist in re-educating us to correct our misunderstandings. I'm sure your
> opinions would be well received by the editors of currently published
> Ceramic Journals".
>
> Best regards,
> Ivor Lewis,
> REDHILL,
> South Australia
>
--
Eric Alan Hansen
Stonehouse Studio Pottery
Alexandria, Virginia
americanpotter.blogspot.com
thesuddenschool.blogspot.com
hansencookbook.blogspot.com
"To me, human life in all its forms, individual and aggregate, is a
perpetual wonder: the flora of the earth and sea is full of beauty and of
mystery which seeks science to understand; the fauna of land and ocean is
not less wonderful; the world which holds them both, and the great universe
that folds it in on everyside, are still more wonderful, complex, and
attractive to the contemplating mind." - Theodore Parker, minister,
transcendentalist, abolitionist (1810-1860)
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