Rachel Campbell on sun 3 apr 05
OK, I'm setting a personal record by posting twice in one week (I usually
only stick up my lurker face once a year or so)...
BUT... I picked up a couple of pints of a commercial cone 6 glaze at NCECA,
which I came home and fired. Gorgeous results, and I put a nice big
pitcher on a shelf in my kitchen. Today I noticed little flakes around the
pot (like broken eggshells, I'd say, since I just got done using up the
kids' Easter eggs), and upon further investigation I found a bare patch on
the pot's shoulder where the glaze evidently flaked off. I've never seen
such a thing before, but I'm guessing this is shivering. (So odd that it
didn't show up initially, and evidently just happened while the pot was
sitting around, minding its own business... it's not like I've done
anything with it in the last 2 days since it came out of the kiln! I may
never trust a visually "good result" again!)
So I have a couple of questions... I see in the archives that Ron Roy
advised someone that a slower firing will help avoid shivering. First, if
I refire the pots, slower this time, will it improve the fit? And second,
given this sadly dramatic result, is it worth it to play with the firing
schedules or should I just write this glaze off, and assume that it is not
a good fit for my clay body? (Since it's a commercial glaze, I can't
really adjust the glaze formula.)
Thanks all!
Rachel Campbell in Odenton MD.
PS-- I know, I know, I could avoid such problems by mixing my own glazes,
and I have grand plans to do so once I have my own "clay space"... right
now I do everything, and store everything in my house, and I'm thinking
that glaze chems and 2 yr. olds don't mix very well. So we do what we can
do... :-)
Jane Murray-Smith on sun 3 apr 05
Try a clay body that doesn't shrink as much...?
----- Original Message -----
From: "Rachel Campbell"
To:
Sent: Saturday, April 02, 2005 10:23 PM
Subject: shivering problem
> OK, I'm setting a personal record by posting twice in one week (I usually
> only stick up my lurker face once a year or so)...
>
> BUT... I picked up a couple of pints of a commercial cone 6 glaze at
> NCECA,
> which I came home and fired. Gorgeous results, and I put a nice big
> pitcher on a shelf in my kitchen. Today I noticed little flakes around
> the
> pot (like broken eggshells, I'd say, since I just got done using up the
> kids' Easter eggs), and upon further investigation I found a bare patch on
> the pot's shoulder where the glaze evidently flaked off. I've never seen
> such a thing before, but I'm guessing this is shivering. (So odd that it
> didn't show up initially, and evidently just happened while the pot was
> sitting around, minding its own business... it's not like I've done
> anything with it in the last 2 days since it came out of the kiln! I may
> never trust a visually "good result" again!)
>
> So I have a couple of questions... I see in the archives that Ron Roy
> advised someone that a slower firing will help avoid shivering. First, if
> I refire the pots, slower this time, will it improve the fit? And second,
> given this sadly dramatic result, is it worth it to play with the firing
> schedules or should I just write this glaze off, and assume that it is not
> a good fit for my clay body? (Since it's a commercial glaze, I can't
> really adjust the glaze formula.)
>
> Thanks all!
>
> Rachel Campbell in Odenton MD.
>
> PS-- I know, I know, I could avoid such problems by mixing my own glazes,
> and I have grand plans to do so once I have my own "clay space"... right
> now I do everything, and store everything in my house, and I'm thinking
> that glaze chems and 2 yr. olds don't mix very well. So we do what we
> can
> do... :-)
>
> ______________________________________________________________________________
> 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.
>
Ron Roy on mon 4 apr 05
Hi Rachel,
Firing slower will probably not cure your problem - what I said is that
sometimes - firing slower near the end of a firing - will improve
glaze/clay adhesion - the glaze will bond better to the clay body.
To answer your question better I need to know how long your glaze firing took.
To say a longer firing will affect the expansion/contraction of clays and
glazes is misleading and would need some strong qualifications to be
reasonable.
RR
>So I have a couple of questions... I see in the archives that Ron Roy
>advised someone that a slower firing will help avoid shivering. First, if
>I refire the pots, slower this time, will it improve the fit? And second,
>given this sadly dramatic result, is it worth it to play with the firing
>schedules or should I just write this glaze off, and assume that it is not
>a good fit for my clay body? (Since it's a commercial glaze, I can't
>really adjust the glaze formula.)
>
>Thanks all!
>
>Rachel Campbell in Odenton MD.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on wed 6 apr 05
I hope this does not look like I am being picky but - shrink is the word we
use for what happens to clay as it dries and is fired - shrinkage.
The word we use for what happens as clay (and glaze) cools is contraction -
and on heating - expansion.
It's just the way we keep those two things separated in our minds.
How much a clay (or glaze) shrinks during drying and firing has nothing to
do with how much it contracts during cooling - after firing
RR
>Try a clay body that doesn't shrink as much...?
>Subject: shivering problem
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Jane Murray-Smith on wed 6 apr 05
Ron, so does this mean that the shivering problem I had with one glaze on
a body that had a huge amount of ball clay.... 85% I believe {Plainsman F97
cone 6) was unrelated to the shrinkage...I also use this body sucessfully
for 2 other glazes that craze on Plainsman M370, or Laguna B-Mix...
There is probably not be a short answer to this...
Just Learning...Jane
----- Original Message -----
From: "Ron Roy"
To:
Sent: Tuesday, April 05, 2005 11:25 PM
Subject: Re: shivering problem
>I hope this does not look like I am being picky but - shrink is the word we
> use for what happens to clay as it dries and is fired - shrinkage.
>
> The word we use for what happens as clay (and glaze) cools is
> contraction -
> and on heating - expansion.
>
> It's just the way we keep those two things separated in our minds.
>
> How much a clay (or glaze) shrinks during drying and firing has nothing to
> do with how much it contracts during cooling - after firing
>
>
> RR
>
>
>>Try a clay body that doesn't shrink as much...?
>
>>Subject: shivering problem
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
> Phone: 613-475-9544
> Fax: 613-475-3513
>
> ______________________________________________________________________________
> 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.
>
Ron Roy on wed 6 apr 05
Hi Jane,
Clay shrinkage has nothing to do with heat expansion and cooling
contraction of fired clay - Clay shrinkage is not reverable in fired clay -
expansion and contraction are exactly reversable.
Send me all this back with the recipes for all three glazes and I will tell
you which one is the problem - send to ronroy@ca.inter.net
RR
>Ron, so does this mean that the shivering problem I had with one glaze on
>a body that had a huge amount of ball clay.... 85% I believe {Plainsman F97
>cone 6) was unrelated to the shrinkage...I also use this body sucessfully
>for 2 other glazes that craze on Plainsman M370, or Laguna B-Mix...
>There is probably not be a short answer to this...
>Just Learning...Jane
>----- Original Message -----
>From: "Ron Roy"
>To:
>Sent: Tuesday, April 05, 2005 11:25 PM
>Subject: Re: shivering problem
>
>
>>I hope this does not look like I am being picky but - shrink is the word we
>> use for what happens to clay as it dries and is fired - shrinkage.
>>
>> The word we use for what happens as clay (and glaze) cools is
>> contraction -
>> and on heating - expansion.
>>
>> It's just the way we keep those two things separated in our minds.
>>
>> How much a clay (or glaze) shrinks during drying and firing has nothing to
>> do with how much it contracts during cooling - after firing
>>
>>
>> RR
>>
>>
>>>Try a clay body that doesn't shrink as much...?
>>
>>>Subject: shivering problem
>>
>> Ron Roy
>> RR#4
>> 15084 Little Lake Road
>> Brighton, Ontario
>> Canada
>> K0K 1H0
>> Phone: 613-475-9544
>> Fax: 613-475-3513
>>
>>
>>__________________________________________________________________________
>>____
>> 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.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Rachel Campbell on thu 7 apr 05
Hi all,
I posted a few days ago about a lovely commercial glaze that a day or two
later shivered chips of glaze off the pot. I was wondering if it was the
firing schedule. (Not super-fast, but not slow either-- just a basic
computer-controlled firng at medium speed with 1/2 hr. soak at the top... it
took 8+ hrs (I don't have my notes with me and don't remember exactly)).
I've been just reading all this and trying to follow it/take it in. Someone
suggested a different clay, and initially I was thinking that I could
perhaps order clay from the same company that manufactures the glazes...
But it sounds like the issue may be a more fundemental one of whether the
glaze is stable or not. Is that true?
There's just so MUCH to learn...I'm trying very hard to focus right now on
improving my throwing and form and aesthetic sense, figuring that I'll delve
deeper into the mysteries of glaze development and firing possibilities
"Later"...(Meaning when I get "set up" better, with a separate "studio"
space/kiln shed, where I can keep glaze chems out of curious 2yr old
fingers.) But it is all inter-related. Well, each little lesson helps...
Rachel in Odenton, MD
where spring EXPLODED yesterday with 80 degree weather and everything in
bloom. It's no doubt just a tease, and it'll be cold and yucky and wet
again soon, but for now it feels like winter is gone!
> -----Original Message-----
> Date: Wed, 6 Apr 2005 14:37:38 -0500
> From: Ron Roy
> Subject: Re: shivering problem
>
> Hi Jane,
>
> Clay shrinkage has nothing to do with heat expansion and cooling
> contraction of fired clay - Clay shrinkage is not reverable in
> fired clay -
> expansion and contraction are exactly reversable.
>
> Send me all this back with the recipes for all three glazes and I
> will tell
> you which one is the problem - send to ronroy@ca.inter.net
>
> RR
>
> >Ron, so does this mean that the shivering problem I had with
> one glaze on
> >a body that had a huge amount of ball clay.... 85% I believe
> {Plainsman F97
> >cone 6) was unrelated to the shrinkage...I also use this body sucessfully
> >for 2 other glazes that craze on Plainsman M370, or Laguna B-Mix...
> >There is probably not be a short answer to this...
> >Just Learning...Jane
> >----- Original Message -----
> >From: "Ron Roy"
> >To:
> >Sent: Tuesday, April 05, 2005 11:25 PM
> >Subject: Re: shivering problem
> >
> >
> >>I hope this does not look like I am being picky but - shrink is the word
> we
> >> use for what happens to clay as it dries and is fired - shrinkage.
> >>
> >> The word we use for what happens as clay (and glaze) cools is
> >> contraction -
> >> and on heating - expansion.
> >>
> >> It's just the way we keep those two things separated in our minds.
> >>
> >> How much a clay (or glaze) shrinks during drying and firing has nothing
> to
> >> do with how much it contracts during cooling - after firing
> >>
> >>
> >> RR
> >>
> >>
> >>>Try a clay body that doesn't shrink as much...?
> >>
> >>>Subject: shivering problem
> >>
> >> Ron Roy
> >> RR#4
> >> 15084 Little Lake Road
> >> Brighton, Ontario
> >> Canada
> >> K0K 1H0
> >> Phone: 613-475-9544
> >> Fax: 613-475-3513
> >>
> >>
John Hesselberth on thu 7 apr 05
> Hi all,
>
> I posted a few days ago about a lovely commercial glaze that a day or
> two
> later shivered chips of glaze off the pot. I was wondering if it was
> the
> firing schedule. (Not super-fast, but not slow either-- just a basic
> computer-controlled firng at medium speed with 1/2 hr. soak at the
> top... it
> took 8+ hrs (I don't have my notes with me and don't remember
> exactly)).
>
> I've been just reading all this and trying to follow it/take it in.
> Someone
> suggested a different clay,
Hi Rachel,
The problem with commercial glazes is that we can't help you figure out
whether it might be the clay or the glaze. If we knew the composition
of the glaze we could help. Since we don't about all we can say is that
you must change one or the other. Unless you really cooled rapidly,
cooling rate is probably not be a major factor. Heating rate in a glaze
firing would not effect shivering propensity.
If you want to tell us specifically what clay and glaze you are using
one of us might have some experience which would help you decide which
to change. But change you must. Shivering is just not an acceptable
defect.
Regards,
John
On Apr 7, 2005, at 11:46 AM, Rachel Campbell wrote:
John Hesselberth
http://www.frogpondpottery.com
http://www.masteringglazes.com
Brant Palley NMCLAY.com on fri 8 apr 05
Shivering is caused by the clay and glaze being incompatible. It is no
fault of yours. I make clay called WH8 (for cone 6) that contains talc.
This clay works great with 95% of Coyote and Laguna glazes. Laguna's new
crackle glazes shiver off every time. Those crackle glazes fit all our
other bodies as they should. Whose fault is it? Blame it on chemistry.
Brant Palley
www.nmclay.com
Our once a year spring sale is April 11-16!
Rachel Campbell on fri 8 apr 05
Hello again...
Well, as it happens, yesterday afternoon I worked up my nerve to email the
company that made the glaze (Coyote Clay & Color) and they got back to me
very quickly... It turns out that 4 of their glazes (including the 2 I
used -- gun metal green and red gold) shiver on "very few clay bodies"-- and
that my clay body is one of them (the same Standard 112 that John Johnson is
having difficulty with, with the MC6 glazes)... (It's nice to know at least
that the result I got was not unexpected ;-)
Sooo-- I'm taking a hammer to a pitcher and a teapot and trying out a
different clay body. And we'll see how that one goes. I just wanted to be
sure that shivering was not a universal indication of an unstable/unsafe
glaze (independant of the clay body) before I tried again... but it sounds
like the Standard 112 clay might have its own issues, and the issue is more
of one of compatibility between glaze and clay (is that correct?).
Thanks so much for your patience and help with my cluelessness-- as so many
have said, clayart is such an amazing resource... where else would "world
famous" experts take the time to help out the unknown and inexperienced?
Rachel in Odenton, MD
>
> ------------------------------
>
> Date: Thu, 7 Apr 2005 14:40:39 -0400
> From: John Hesselberth
> Subject: Re: shivering problem
>
> > Hi all,
> >
> > I posted a few days ago about a lovely commercial glaze that a day or
> > two
> > later shivered chips of glaze off the pot. I was wondering if it was
> > the
> > firing schedule. (Not super-fast, but not slow either-- just a basic
> > computer-controlled firng at medium speed with 1/2 hr. soak at the
> > top... it
> > took 8+ hrs (I don't have my notes with me and don't remember
> > exactly)).
> >
> > I've been just reading all this and trying to follow it/take it in.
> > Someone
> > suggested a different clay,
> Hi Rachel,
>
> The problem with commercial glazes is that we can't help you figure out
> whether it might be the clay or the glaze. If we knew the composition
> of the glaze we could help. Since we don't about all we can say is that
> you must change one or the other. Unless you really cooled rapidly,
> cooling rate is probably not be a major factor. Heating rate in a glaze
> firing would not effect shivering propensity.
>
> If you want to tell us specifically what clay and glaze you are using
> one of us might have some experience which would help you decide which
> to change. But change you must. Shivering is just not an acceptable
> defect.
>
> Regards,
>
> John
> On Apr 7, 2005, at 11:46 AM, Rachel Campbell wrote:
> John Hesselberth
> http://www.frogpondpottery.com
> http://www.masteringglazes.com
dkat on fri 8 apr 05
We have had problems with the 112. Our studio is one that has a wide range of skill and a great many beginning student so it is difficult to separate out when it is a problem with materials or when it is a problem with the use of the materials. The cracks we have been getting with the 112 have been odd to say the least. Not your typical S cracks. We have been getting crawling and pinholing with our glazes (including the MC6 glazes) but the cause has not been tracked down yet so I can't say if it is the glaze on 112, the firing (which may be too high and with not enough of a soak), the clay body, application or what. I was told that 112 had been mixed with a 'bad' batch of fireclay or something of the like but that is 3rd hand at best.
----- Original Message -----
From: Rachel Campbell
To: CLAYART@LSV.CERAMICS.ORG
Sent: Friday, April 08, 2005 5:24 PM
Subject: Re: shivering problem
Hello again...
Well, as it happens, yesterday afternoon I worked up my nerve to email the
company that made the glaze (Coyote Clay & Color) and they got back to me
very quickly... It turns out that 4 of their glazes (including the 2 I
used -- gun metal green and red gold) shiver on "very few clay bodies"-- and
that my clay body is one of them (the same Standard 112 that John Johnson is
having difficulty with, with the MC6 glazes)... (It's nice to know at least
that the result I got was not unexpected ;-)
Sooo-- I'm taking a hammer to a pitcher and a teapot and trying out a
different clay body. And we'll see how that one goes. I just wanted to be
sure that shivering was not a universal indication of an unstable/unsafe
glaze (independant of the clay body) before I tried again... but it sounds
like the Standard 112 clay might have its own issues, and the issue is more
of one of compatibility between glaze and clay (is that correct?).
Thanks so much for your patience and help with my cluelessness-- as so many
have said, clayart is such an amazing resource... where else would "world
famous" experts take the time to help out the unknown and inexperienced?
Rachel in Odenton, MD
>
> ------------------------------
>
> Date: Thu, 7 Apr 2005 14:40:39 -0400
> From: John Hesselberth
> Subject: Re: shivering problem
>
> > Hi all,
> >
> > I posted a few days ago about a lovely commercial glaze that a day or
> > two
> > later shivered chips of glaze off the pot. I was wondering if it was
> > the
> > firing schedule. (Not super-fast, but not slow either-- just a basic
> > computer-controlled firng at medium speed with 1/2 hr. soak at the
> > top... it
> > took 8+ hrs (I don't have my notes with me and don't remember
> > exactly)).
> >
> > I've been just reading all this and trying to follow it/take it in.
> > Someone
> > suggested a different clay,
> Hi Rachel,
>
> The problem with commercial glazes is that we can't help you figure out
> whether it might be the clay or the glaze. If we knew the composition
> of the glaze we could help. Since we don't about all we can say is that
> you must change one or the other. Unless you really cooled rapidly,
> cooling rate is probably not be a major factor. Heating rate in a glaze
> firing would not effect shivering propensity.
>
> If you want to tell us specifically what clay and glaze you are using
> one of us might have some experience which would help you decide which
> to change. But change you must. Shivering is just not an acceptable
> defect.
>
> Regards,
>
> John
> On Apr 7, 2005, at 11:46 AM, Rachel Campbell wrote:
> John Hesselberth
> http://www.frogpondpottery.com
> http://www.masteringglazes.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.
Ron Roy on sat 9 apr 05
Hi Brant,
Something strange here - if a glaze is crazed (crackle) that is the
opposite problem from shivering.
The only time I have ever seen both shivering and crazing together is when
lithium carb is in the glaze.
Just wanted to confirm that you are getting shivering and crazing at the
same time.
RR
>Shivering is caused by the clay and glaze being incompatible. It is no
>fault of yours. I make clay called WH8 (for cone 6) that contains talc.
>This clay works great with 95% of Coyote and Laguna glazes. Laguna's new
>crackle glazes shiver off every time. Those crackle glazes fit all our
>other bodies as they should. Whose fault is it? Blame it on chemistry.
>
>Brant Palley
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Brant Palley NMCLAY.com on sun 10 apr 05
I think the glaze is crazing so much it can't hang on to the clay. I dont
know if lithium is involved as i don't have the glaze formulas. Some of
coyote's glazes that are not fitting do contain lithium. Using talc in
midrange and high fire bodies is always risky.
Brant
www.nmclay.com
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