Eleanora Eden on fri 25 aug 06
Hi Lili, Ron, and all,
I have been asking these questions about clay additives and concluded that
the only use for petalite in a clay body would be for thermal shock resistance.
It is not clear to me that a small addition of petalite (5%) would be either good, bad,
or just indifferent in making up clay bodies for all around strength and performance.
Eleanora
>Dear Lili,
>
>Bodies made with petalite or spodumene (fluxed with lithium oxide) will
>have very low expansion contraction rates - very good for making stuff like
>ovenware.
>
>They need a lot of skill to fire consistently - excellent firing control
>and are very difficult to eliminate crazing on.
>
>I would say beyond the scope of most studio potters to work with.
>
>There is an excellent discussion of them in Ceramic Science for the Potter
>by Lawrence and West - republished by Axner (Gentle Breeeze Publishing)
>
>Vermiculite is expanded mica and might be added to a clay body if you
>wanted to lighten it - quite different from Petalite with is like a spar
>but has lithium instead of KNaO.
>
>RR
>
>
>>Then. Again a long time ago there were articles and mentions--I think Wm
>>Hunt did one--of clay bodies with added petalite and/or added vermiculite.
>>Again these have disappeared from the radar screen. Is there a reason?
>>Again is there a danger here that was not thought about, known at the time?
>
>Ron Roy
>RR#4
>15084 Little Lake Road
>Brighton, Ontario
>Canada
>K0K 1H0
>
>______________________________________________________________________________
>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.
--
Bellows Falls Vermont
www.eleanoraeden.com
David Beumee on fri 25 aug 06
Hi Eleanora,
Val Cushing discovered in his thesis work that a flameware body was possible with a high percentage (60 - 70%) addition of Petalite, making the body so low in thermal expansion that it would take heating on a direct flame and be able to be taken off the stove and immersed in water without cracking. There are four Petalite bodies listed on page 13 of Cushing's Handbook, third edition.
Here's Body #2,
2.8% absorption @ cone 13:
55 Petalite
45 China Clay
David Beumee
-------------- Original message ----------------------
From: Eleanora Eden
> Hi Lili, Ron, and all,
>
> I have been asking these questions about clay additives and concluded that
> the only use for petalite in a clay body would be for thermal shock resistance.
>
> It is not clear to me that a small addition of petalite (5%) would be either
> good, bad,
> or just indifferent in making up clay bodies for all around strength and
> performance.
>
> Eleanora
>
>
>
> >Dear Lili,
> >
> >Bodies made with petalite or spodumene (fluxed with lithium oxide) will
> >have very low expansion contraction rates - very good for making stuff like
> >ovenware.
> >
> >They need a lot of skill to fire consistently - excellent firing control
> >and are very difficult to eliminate crazing on.
> >
> >I would say beyond the scope of most studio potters to work with.
> >
> >There is an excellent discussion of them in Ceramic Science for the Potter
> >by Lawrence and West - republished by Axner (Gentle Breeeze Publishing)
> >
> >Vermiculite is expanded mica and might be added to a clay body if you
> >wanted to lighten it - quite different from Petalite with is like a spar
> >but has lithium instead of KNaO.
> >
> >RR
> >
> >
> >>Then. Again a long time ago there were articles and mentions--I think Wm
> >>Hunt did one--of clay bodies with added petalite and/or added vermiculite.
> >>Again these have disappeared from the radar screen. Is there a reason?
> >>Again is there a danger here that was not thought about, known at the time?
> >
> >Ron Roy
> >RR#4
> >15084 Little Lake Road
> >Brighton, Ontario
> >Canada
> >K0K 1H0
> >
> >______________________________________________________________________________
> >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.
>
>
> --
> Bellows Falls Vermont
> www.eleanoraeden.com
>
> ______________________________________________________________________________
> 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.
Amanda Blum - Howling Zoe Productions on fri 25 aug 06
I actually studied with Val at RISD. Oddly, he didn't teach us about
flameware, Frank Bosco did. Petalite is indeed wonderful for a flameware (I
was just perusing my recipes for flameware today).
Flameware though, in my experience, has such limited application because
once you make a clay that is flame resistant, it has zero plasticity and is
almost unworkable.
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of David Beumee
Sent: Friday, August 25, 2006 2:16 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: petalite in clay bodies
Hi Eleanora,
Val Cushing discovered in his thesis work that a flameware body was
possible with a high percentage (60 - 70%) addition of Petalite, making the
body so low in thermal expansion that it would take heating on a direct
flame and be able to be taken off the stove and immersed in water without
cracking. There are four Petalite bodies listed on page 13 of Cushing's
Handbook, third edition.
Here's Body #2,
2.8% absorption @ cone 13:
55 Petalite
45 China Clay
David Beumee
-------------- Original message ----------------------
From: Eleanora Eden
> Hi Lili, Ron, and all,
>
> I have been asking these questions about clay additives and concluded that
> the only use for petalite in a clay body would be for thermal shock
resistance.
>
> It is not clear to me that a small addition of petalite (5%) would be
either
> good, bad,
> or just indifferent in making up clay bodies for all around strength and
> performance.
>
> Eleanora
>
>
>
> >Dear Lili,
> >
> >Bodies made with petalite or spodumene (fluxed with lithium oxide) will
> >have very low expansion contraction rates - very good for making stuff
like
> >ovenware.
> >
> >They need a lot of skill to fire consistently - excellent firing control
> >and are very difficult to eliminate crazing on.
> >
> >I would say beyond the scope of most studio potters to work with.
> >
> >There is an excellent discussion of them in Ceramic Science for the
Potter
> >by Lawrence and West - republished by Axner (Gentle Breeeze Publishing)
> >
> >Vermiculite is expanded mica and might be added to a clay body if you
> >wanted to lighten it - quite different from Petalite with is like a spar
> >but has lithium instead of KNaO.
> >
> >RR
> >
> >
> >>Then. Again a long time ago there were articles and mentions--I think
Wm
> >>Hunt did one--of clay bodies with added petalite and/or added
vermiculite.
> >>Again these have disappeared from the radar screen. Is there a reason?
> >>Again is there a danger here that was not thought about, known at the
time?
> >
> >Ron Roy
> >RR#4
> >15084 Little Lake Road
> >Brighton, Ontario
> >Canada
> >K0K 1H0
> >
>
>___________________________________________________________________________
___
> >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.
>
>
> --
> Bellows Falls Vermont
> www.eleanoraeden.com
>
>
____________________________________________________________________________
__
> 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.
____________________________________________________________________________
__
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
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Lee Love on sun 27 aug 06
Something important to remember is that not all members live in the
States. For example, I can buy petalite cheaply, but cannot buy
Spodumene. Spodumene is available from one source here, but it is only
sold to industry (I have inqured with little success.)
--
Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
Ron Roy on sun 27 aug 06
Hi Eleanor,
First I should explain - why I would not use petalite - if I was adding
Lithium to a glaze or clay - it does not have much Li2O - like about 4.3 -
and it comes from South Africa I think - so it is expensive Lithium -
spodumene would make more sense for us here in NA - as it would have more -
over 7% Li2O and it is mined here. Even the Aussi spod would be a better
deal - again - over 7% Li2O.
If you are asking - what would happen if lithium (in the form of Petalite
or Spodumene) were subbed into a body - at the expense of some of the spar?
The expansion/contraction rate of lithium is much lower than the
expansion/contraction rate of KNaO - so the expansion rate of that clay
body would decrease.
This is an advantage if the ware is to be subjected to uneven heating -
lowering expansion will then lessen the chances of cracking due to heat
shock. An advantage when making oven ware.
Bodies with lower expansions need to have glazes of lower expansion if
crazing is to be avoided - again - lithium can be used in glazes as well.
If you are asking - will any clay body be made stringer with the addition
of Petalite - that is different - I assume you mean - keeping the
absorbency in the desired amount - and not just adding more flux and over
melting.
Will the body be stronger given the above caveat - I would not think so -
but it would be more expensive for sure.
RR
>Hi Lili, Ron, and all,
>
>I have been asking these questions about clay additives and concluded that
>the only use for petalite in a clay body would be for thermal shock resistance.
>
>It is not clear to me that a small addition of petalite (5%) would be
>either good, bad,
>or just indifferent in making up clay bodies for all around strength and
>performance.
>
>Eleanora
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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