Bill Merrill on thu 16 aug 07
How long has the dilatometer been used in Ceramics? If it has only been
used in the 20th century, there were a lot of good pots that were made
before then and without the aid of a dilatometer. Modern science is
wonderful, but there seems to me to be a fear factor when we talk about
cristobalite. I hope people don't quit making pots because they're
paranoid about cristobalite. I have always fluxed my clay bodies and
made sure the glazes "fit" the clay body I use. Do many of you have
cristobalite problems? Are your glazes shivering? Are your glazes
crazing when you don't want the crazing. Do your pots break if you open
your kiln (after glaze firing) around 300 degrees? Are you fast firing
and crash cooling? Cristobalite is natural occurring part of pottery.
We just have to be aware of what can happen and be prepared to make
changes. Someone said "you can't worry about what hasen't happened yet"
If you haven't experienced those heart breaks, great! Hopefully the
companies supplying clays produce a good product(like Ron Roy). Ron is
seriously interested in helping potters that have had those problems.
For those who mix our own clays we need know enough about materials to
prevent or correct any problem that arises and can turn to knowledgeable
sources.=20
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Val Cushing's Handbook offers a life time of knowledge for potters. In
looking at my notes from his class, the notes I took are revealed in his
handbook. The handbook covers clay, glazes, firing etc. at various
temperatures. The handbook now costs $25 and that includes mailing
costs.
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Val Cushing
1497 Waterwell Road
Alfred Station, NY
14803
=20
The other books that are so good and very pragmatic are the books by
Daniel Rhodes.
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Stoneware and Porcelain: The art of High Fire Ceramics Chilton
Books
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Clay and glazes for the Potter Chilton Books
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Kilns, Design, Construction and operation Chilton Books
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There are so many good books out there and I own so many others. I am
just going back to my days when I didn't know anything and remember the
excitement and disappointments of my early days. Those were wonderful
times. I think as a group of potters that we are looking for the "Holy
Grail" within the field we care for so much. Here's hoping we always
keep looking! Keep making pots, the best ones are still in you.
=20
Regards to all,
=20
Bill Merrill
=20
Billm@pcadmin.ctc.edu
=20
=20
=20
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Ron Roy on tue 21 aug 07
Hi Bill,
I am interested in helping to make sure that potters have a better chance
to make a living at our craft. I think we as a group represent something
important - to be specific - craftsmanship is a worthy goal for everyone.
Because I have been a clay maker and now work for a clay company I have a
better than average idea about what is happening out there. Pots cracking
in use and glazes shivering. That has a bad effect on pottery sales for
everyone.
I think it is important to point out to potters - and clay makers that
there can be problems and we should know about them.
Not many clay companies have dilatometers - and some that have them don't
use them. The "normal" way that problems are found is potters getting pots
returned that don't do what they are supposed to do.
We are dealing with a lot of technical problems when we make pots - and not
many of us have the use of a dilatometer. Every ceramic factory in the
world has one - or they would be out of business.
Remember - we are laminating clays and glazes and they all have different
expansion/contraction rates. In the old days potters learned by trial and
error - don't use this glaze with that clay - the pots will break. Now we
have our choice of clay bodies and glaze - an infinite choice - the best of
all possible worlds - except some are not going to work together.
We also have calculation software and some who use it share their insights.
We also have clayart - and we all learn something new every day - what a
glorious time to be a potter.
RR
Bill Merrill said -
>If you haven't experienced those heart breaks, great! Hopefully the
>companies supplying clays produce a good product(like Ron Roy). Ron is
>seriously interested in helping potters that have had those problems.
>For those who mix our own clays we need know enough about materials to
>prevent or correct any problem that arises and can turn to knowledgeable
>sources.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Earl Krueger on tue 21 aug 07
Ron, John,
In "Mastering Cone 6 Glazes", chapter 5 "Fitting
Glazes to Your Clay Body" you give recipes for
glazes of various expansion that you can use to
determine an approximate expansion for a clay
body. Can the reverse be done? That is, could
one develop recipes for various clay bodies that
could be used to check the expansion of a glaze?
Thanks...
earl...
Earl Krueger
Elmira, Oregon, usa
John Hesselberth on tue 21 aug 07
On Aug 21, 2007, at 2:47 PM, Earl Krueger wrote:
> In "Mastering Cone 6 Glazes", chapter 5 "Fitting
> Glazes to Your Clay Body" you give recipes for
> glazes of various expansion that you can use to
> determine an approximate expansion for a clay
> body. Can the reverse be done? That is, could
> one develop recipes for various clay bodies that
> could be used to check the expansion of a glaze?
Hi Earl,
I hope Ron will chime in too, but I think the answer is yes. In fact
you could probably just pick from existing commercial clay bodies and
get a range by seeing which glaze in that series fits them best. Ron
could probably do it a bit more systematically since he is a clay
body formulator of considerable skill.
Regards,
John
John Hesselberth
www.frogpondpottery.com
"Man is a tool-using animal....without tools he is nothing, with
tools he is all" .... Thomas Carlyle
Ron Roy on wed 22 aug 07
Hi Earl,
I have often thought I would like to understand why some bodies expand and
contract more than others but have never had the time to even start that
one.
The bottom line is - I don't know if it's feasable or not.
I tend to think it would not be as reliable as using glazes because of how
clays vary from lot to lot.
Also because heat work and time have such a profound effect on expansion -
free quartz, cristobalite for instance - the clays would have to be fired
and cooled in the same way each time - because we are dealing with unmelted
material.
If you would like to do some testing I would be willing to do my part -
like measure the clays and some analysis - you interested?
RR
>Ron, John,
>
>In "Mastering Cone 6 Glazes", chapter 5 "Fitting
>Glazes to Your Clay Body" you give recipes for
>glazes of various expansion that you can use to
>determine an approximate expansion for a clay
>body. Can the reverse be done? That is, could
>one develop recipes for various clay bodies that
>could be used to check the expansion of a glaze?
>
>Thanks...
>earl...
>
>Earl Krueger
>Elmira, Oregon, usa
>
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Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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