Jonathan Pennington on fri 25 jan 02
Sorry about that stupid post to the entire list asking if a single
person has sold a Giffen Grip- that was *meant* for offlist.
A friend of mine just recieved a mug of mine, and commissioned
more. She said that she bought a set of 4 mugs from an unnamed potter
(honestly, she didn't name him/her) this summer and 3 of the 4 handles
have fallen off. I may have been somewhat out of line, being a
relative baby to potting, but I told her that to me that was
*completely unacceptable.* I said that if my handles came off my pots,
I would immediately replace it, and that she should tell the potter-
if only so that the potter *knows* that there was a problem.
Am I out to lunch on this? I've thrown a couple of my mugs (green,
bisqued and glazed) on the concrete to see what they'd do, and without
fail the handle attachment holds while the handle/mug breaks. Would
anyone here expect a handle to come off- especially in less than 1
year?
-J
--
Jonathan Pennington | jwpennin@bellsouth.net
"There are no pots, there is only clay." -original
"It's hard to take life too seriously
when you realize yours is a joke." -also original
Dannon Rhudy on sat 26 jan 02
.......... bought a set of 4 mugs from an unnamed potter
...... this summer and 3 of the 4 handles
>have fallen off. .....she should tell the potter-
.........Would
>anyone here expect a handle to come off........
Expectations aside, the handle should NOT part from the
cup at the attachment. The maker should certainly know, and
immediately. Surely others have told the maker before, but
perhaps not. Handles that "come off" are a lawsuit waiting
to happen. There are a number of possibilities here, among
them that the maker simply does not know how to attach a
handle properly. Another might be that the mugs are bought
as bisque, and there is some quality control problem. Whatever
it is, it should be resolved immediately. The maker needs to
know.
regards
Dannon Rhudy
Roger Korn on sat 26 jan 02
Hi Jonathan,
The handle/mug join "should" be one of the strongest points on the pot, right up
there with the cup/foot transition area, because the shape of a faired-in
attachment is exceptionally good for distributing stress over a large area, hence
preventing "stress riser" points that initiate failure. Most of my failed joins are
the result of dramatic difference in dryness of the handle and bowl, coupled with
too fast drying to bone dry, such that the difference in shrinkage pulled them
apart. If the assembled bowl/handle is placed in a plastic bag for several days to
allow the moisture content to equaliz(s)e before drying continues, even the initial
difference in dryness shouldn't cause problems.
Hope this offers some ideas,
Roger
Jonathan Pennington wrote:
> Sorry about that stupid post to the entire list asking if a single
> person has sold a Giffen Grip- that was *meant* for offlist.
>
> A friend of mine just recieved a mug of mine, and commissioned
> more. She said that she bought a set of 4 mugs from an unnamed potter
> (honestly, she didn't name him/her) this summer and 3 of the 4 handles
> have fallen off. I may have been somewhat out of line, being a
> relative baby to potting, but I told her that to me that was
> *completely unacceptable.* I said that if my handles came off my pots,
> I would immediately replace it, and that she should tell the potter-
> if only so that the potter *knows* that there was a problem.
>
> Am I out to lunch on this? I've thrown a couple of my mugs (green,
> bisqued and glazed) on the concrete to see what they'd do, and without
> fail the handle attachment holds while the handle/mug breaks. Would
> anyone here expect a handle to come off- especially in less than 1
> year?
>
> -J
> --
> Jonathan Pennington | jwpennin@bellsouth.net
> "There are no pots, there is only clay." -original
> "It's hard to take life too seriously
> when you realize yours is a joke." -also original
>
> ______________________________________________________________________________
> 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.
--
Roger Korn
McKay Creek Ceramics
In AZ: PO Box 463
4215 Culpepper Ranch Rd
Rimrock, AZ 86335
928-567-5699 <-
In OR: PO Box 436
31330 NW Pacific Ave.
North Plains, OR 97133
503-647-5464
Lois Ruben Aronow on sat 26 jan 02
I agree that this is totally unacceptable. Unlike having a rim or a
foot ring chip, the handle falling off says to me that the mug was
poorly made. It is a flaw in the construction, rather than something
that can, and does, happen through use.
2 years ago I purchased a mug from a Famous Potter, knowing full well
the handle was my least favourite part of the mug. But I liked the
mug, and always buy mugs to add to my collection.
Lo and behold, the handle actually snapped in half (yes, in half!)
while I was doing nothing more strenuous than pouring myself a cup of
java. I still love this potter's decorative pieces, though. Maybe
mugs aren't her forte.
Ned Ludd on sat 26 jan 02
Lois Ruben Aronow wrote:
>I agree that this is totally unacceptable. Unlike having a rim or a
>foot ring chip, the handle falling off says to me that the mug was
>poorly made. It is a flaw in the construction, rather than something
>that can, and does, happen through use.
>
>2 years ago I purchased a mug from a Famous Potter, knowing full well
>the handle was my least favourite part of the mug. But I liked the
>mug, and always buy mugs to add to my collection.
>
>Lo and behold, the handle actually snapped in half (yes, in half!)
>while I was doing nothing more strenuous than pouring myself a cup of
>java. I still love this potter's decorative pieces, though. Maybe
>mugs aren't her forte.
Hi Lois and others
I've been making mugs for years with no problem (like this) but
something really odd happened lately. Wife gave a guest hot tea in a
recently fired shino mug of mine, that had only been used about five
times... before he could drink from it there was a blur, a crash, and
the startled gentleman was left gripping a couple of inches of
handle, his coffee on the floor.
The tea had come from the pot, not a microwave oven. I examined the
pieces thoroughly as I could without a magnifying glass. (I also
checked other mugs from the same firing with the same shino glaze.)
The break was very clean and sheer, perpendicular across the handle..
top edge and lower edge, about a half inch out from the attachment
points. The glaze layer was not unduly thick. The handle was about
the thickness of a thumb. There was no sign at all of crazing or
crawling or dunting... nor have we ever had poltergeist activity in
this house!
I still am not sure why it happened. I incline to assume that the
expansion coefficients of the shino and the clay are too far apart
and the cooled pot is under excessive tension. Are there other
feasible explanations? Luckily I had not put out any of this batch
with the (new to me) shino for sale, and obviously I won't. I am SO
glad this did not happen to my customer(s)!
best
Ned
Ron Roy on mon 28 jan 02
Hi Ned,
This sounds like it could be a clay/glaze fit problem - it seems the most
likely possibility to me - if you would like me to give a more educated
opinion I need to calculate the expansion - I need the recipe of the glaze
and the type of clay used, the kind of firing and how long from 1100C up
and how fast a cool.
RR
>I've been making mugs for years with no problem (like this) but
>something really odd happened lately. Wife gave a guest hot tea in a
>recently fired shino mug of mine, that had only been used about five
>times... before he could drink from it there was a blur, a crash, and
>the startled gentleman was left gripping a couple of inches of
>handle, his coffee on the floor.
>
>The tea had come from the pot, not a microwave oven. I examined the
>pieces thoroughly as I could without a magnifying glass. (I also
>checked other mugs from the same firing with the same shino glaze.)
>The break was very clean and sheer, perpendicular across the handle..
>top edge and lower edge, about a half inch out from the attachment
>points. The glaze layer was not unduly thick. The handle was about
>the thickness of a thumb. There was no sign at all of crazing or
>crawling or dunting... nor have we ever had poltergeist activity in
>this house!
>
>I still am not sure why it happened. I incline to assume that the
>expansion coefficients of the shino and the clay are too far apart
>and the cooled pot is under excessive tension. Are there other
>feasible explanations? Luckily I had not put out any of this batch
>with the (new to me) shino for sale, and obviously I won't. I am SO
>glad this did not happen to my customer(s)!
>
>best
>
>Ned
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
Working Potter on thu 7 feb 02
I do not have a solution to this but many years ago, I took a caserole made
by a friend out of a 350 degree oven filled 1'' below the rim with a hot
meal and both handles gave way [not at the join] and the only thing I could
figure a the time was that his body had a very high iron content as he
added iron oxide to deepen the color.his glaze was a satin mat with chrome
and rutile as colorants and the reduction looked a bit heavy but with
attracive looking results.I was not hurt[except our meal loss, but was
astonished at what happened and that was either the first or second use of
the caserole.Go figure.
Ron Roy on sat 9 feb 02
Hi iron bodies are the worst for cristobalite - the iron is a flux in
reduction so you can't have as much KNaO - which eats cristobalite.
The kind of silica we get these days is so fine it converts into
cristobalite very easily - a clue to controlling it.
Easy to find out if there is cristobalite in fired clay - measure a sample
in a dilatometer - the curve will show you both cristobalite and quartz.
RR
>I do not have a solution to this but many years ago, I took a caserole made
> by a friend out of a 350 degree oven filled 1'' below the rim with a hot
>meal and both handles gave way [not at the join] and the only thing I could
>figure a the time was that his body had a very high iron content as he
>added iron oxide to deepen the color.his glaze was a satin mat with chrome
>and rutile as colorants and the reduction looked a bit heavy but with
>attracive looking results.I was not hurt[except our meal loss, but was
>astonished at what happened and that was either the first or second use of
>the caserole.Go figure.
>
>______________________________________________________________________________
>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 Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
Wes Rolley on sun 10 feb 02
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At 11:37 AM 2/9/02 -0400, you wrote:
>From: Ron Roy
>Subject: Re: Mug handles breaking/ stupid post.
>To: CLAYART@LSV.CERAMICS.ORG
>
>
>Hi iron bodies are the worst for cristobalite - the iron is a flux in
>reduction so you can't have as much KNaO - which eats cristobalite.
Ron, how much of a problem would this be in an electric firing? My
experience is that it is much less. I do use a body that is high in
Newman's Red.
Wes
Wesley C. Rolley
17211 Quail Court
Morgan Hill, CA 95037
wesley@rolley.com
(408)778-3024
--=======52C8672F=======--
Ron Roy on wed 13 feb 02
Yes - you are right - it's when the iron is reduced that it becomes a big
time flux and so you can't have as much KNaO - which is part of the control
for cristobalite - the othe BIG factor is how much fine silica you have in
the body.
The slower you fire above cone 6 - and the slower you cool in that rage -
the more cristobalite.
RR
>>Hi iron bodies are the worst for cristobalite - the iron is a flux in
>>reduction so you can't have as much KNaO - which eats cristobalite.
>
>Ron, how much of a problem would this be in an electric firing? My
>experience is that it is much less. I do use a body that is high in
>Newman's Red.
>
>Wes
>
>
>Wesley C. Rolley
>17211 Quail Court
>Morgan Hill, CA 95037
>wesley@rolley.com
>(408)778-3024
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
Tony Ferguson on fri 29 mar 02
Hi guys,
It was my understanding that a high iron body in a long firing 24 hours +
like wood firing would present a potential issue for crystobalite? I seem
to have been pretty lucky so far. I doubt an electric firing would pose any
problems--of course this may depend on if you have heaping amounts of iron
in it. I don't know. Go ask Vince!
Thank you!
Tony Ferguson
Stoneware, Porcelain, Raku
www.aquariusartgallery.com
Web Site, Marketing & Photographic Services for Artists
Workshops available
218-727-6339
315 N. Lake Ave
Apt 312
Duluth, MN 55806
----- Original Message -----
From: "Wes Rolley"
To:
Sent: Sunday, February 10, 2002 8:21 AM
Subject: Re: Mug handles breaking/ stupid post.
> At 11:37 AM 2/9/02 -0400, you wrote:
> >From: Ron Roy
> >Subject: Re: Mug handles breaking/ stupid post.
> >To: CLAYART@LSV.CERAMICS.ORG
> >
> >
> >Hi iron bodies are the worst for cristobalite - the iron is a flux in
> >reduction so you can't have as much KNaO - which eats cristobalite.
>
> Ron, how much of a problem would this be in an electric firing? My
> experience is that it is much less. I do use a body that is high in
> Newman's Red.
>
> Wes
>
>
> Wesley C. Rolley
> 17211 Quail Court
> Morgan Hill, CA 95037
> wesley@rolley.com
> (408)778-3024
>
>
Ron Roy on tue 2 apr 02
Hi Wes,
I can't believe I'm responding to a post I wrote almost two months ago -
I'm having trouble deciding to answer at all - good grief!
I am assuming you are firing to cone 10 - at 6 there does not seem to be a
problem - at least with any cone 6 bodies I have measured.
I tend to think cristobalite is - normally less of a problem in oxidation -
the iron is not a strong flux in that case and normal amounts of KNaO can
be used to vitrify the clay -HOWEVER - it is not always the case and the
way to find out is to measure the clay with a dilatometer.
Much depends on the amount of microfine silica added to the body - the more
micro fine silica the more KNaO you need to counter it's propensity to
convert to cristobalite.
If you are fluxing with MgO or CaO at cone 10 I'll bet you will have some.
If you are interested in finding out for sure post your body recipe to me
and I'll take a guess - or contact me privately and I will tell you how
much it will cost to have a sample measured and how to make the sample.
RR
>> At 11:37 AM 2/9/02 -0400, you wrote:
>> >From: Ron Roy
>> >Subject: Re: Mug handles breaking/ stupid post.
>> >To: CLAYART@LSV.CERAMICS.ORG
>> >
>> >
>> >Hi iron bodies are the worst for cristobalite - the iron is a flux in
>> >reduction so you can't have as much KNaO - which eats cristobalite.
>>
>> Ron, how much of a problem would this be in an electric firing? My
>> experience is that it is much less. I do use a body that is high in
>> Newman's Red.
>>
>> Wes
Ron Roy
RR #4
15084 Little Lake Road
Brighton
Ontario
Canada - K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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