Paul Lewing on mon 17 dec 07
On Dec 17, 2007, at 11:23 AM, Keba M Hitzeman wrote:
I found some information on crazing in the archives, but does a food-
safe
glaze that crazes make that piece not food safe?
One of the problems in answering your question is that there is no
set definition of "food-safe". As someone pointed out, it usually
refers to the ingredients of the glaze itself leaching into food. I
assume that what you are asking here is about whether the craze lines
will harbor bacteria. We've discussed this before, and the consensus
has been that it's better to avoid crazing if you can, but some
people think germs can live in there and then come out and hurt you,
and others do not. It was even reported once, I believe, that the
problem was so severe that enough food oils could accumulate to
flavor subsequent servings of food.
My opinion is that if we have germs in our dinnerware's glazes that
can survive the dishwasher and the microwave, we're in bigger trouble
than having crazed glazes. Some have said that you might be legally
liable if someone ate food off your crazed dinnerware and got sick.
Nonsense. The first question anyone would ask in that situation
would be "You ate WHAT FOOD off that plate?" It always amazes me
when people worry about the germs that might be lurking in those
cracks, but they will eat a hamburger or a salad off that plate
without a second thought. How many people have you heard of lately
who have died from eating tainted food? And have you ever heard of
anyone being made ill by germs harbored in glazes? Of course not.
Just my two cents worth.
Paul Lewing
www.paullewingtile.com
Keba M Hitzeman on mon 17 dec 07
I found some information on crazing in the archives, but does a food-safe
glaze that crazes make that piece not food safe?
I was rinsing out some pieces and as I dried them, they started "popping",
for lack of a better word - it sounded almost like sleet hitting a window.
I held them up to the light, and saw craze lines where the water had been.
After they dried, I checked the pieces again, and the craze lines were gone.
The bottle says "food safe" (it's Amaco's Crystaltex "caramel"), but now I'm
second guessing...
Thanks!
Keba in Dayton OH
Steve Slatin on mon 17 dec 07
Keba -- crazing may be invisible without being 'gone.'
When I have doubts, I take a test piece and pour a bit
of ink into it. I let it sit for 15 seconds or so, and pour
it back into the jar.
The ink will clean readily off of the surface with a rag
or paper towel, but the ink will sink into the gaps
if there are any. I can't think of a plausible scenario
under which crazing would self-cure at room temperature.
(I have had glazes that crazed if fired once and not if
fired twice. Perhaps if I'd fired to a higher temp the
first time? But there are only so many variables one
person can experiment with.)
Best -- Steve Slatin
Keba M Hitzeman wrote:
I found some information on crazing in the archives, but does a food-safe
glaze that crazes make that piece not food safe?
I was rinsing out some pieces and as I dried them, they started "popping",
for lack of a better word - it sounded almost like sleet hitting a window.
I held them up to the light, and saw craze lines where the water had been.
After they dried, I checked the pieces again, and the craze lines were gone.
The bottle says "food safe" (it's Amaco's Crystaltex "caramel"), but now I'm
second guessing...
Thanks!
Keba in Dayton OH
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Lynn Goodman Porcelain Pottery on mon 17 dec 07
On Dec 17, 2007, at 2:23 PM, Keba M Hitzeman wrote:
> I found some information on crazing in the archives, but does a
> food-safe
> glaze that crazes make that piece not food safe?
Hi Keba,
It depends on your clay: how much absorption does it have? You didn't
say what type of clay you're using and what temp you're firing at. I
wouldn't consider crazed glaze on earthenware to be food-safe EVER--
food oils and juices can be absorbed into the clay via crazed glaze
and ferment or grow bacteria. This could make you very sick! If you
are using stoneware and it is FULLY mature (hence, has little
absorption) it's probably ok as long as you are very careful about
cleaning. Look at the info for your clay to find out what its
absorption is at the temp you are firing at.
Lynn
Lynn Goodman
Fine Porcelain Pottery
Cell 347-526-9805
www.lynngoodmanporcelain.com
John Hesselberth on mon 17 dec 07
Hi Keba,
You'll probably get a wide variety of opinions on this. Mine: I doubt
that it has much effect on whether or not you are going to endanger
someone. There are other glaze defects that bother me much more (like
shivering).
But I also have to say it indicates, to me, poor craftsmanship if it
is on a food bearing surface. On the outside of a mug it can be a
nice decorative effect; on the inside, to me, it is poor
craftsmanship. The exception to that, in my mind, are salt glazed
pieces where crazing is almost impossible to avoid.
One fact: it does lower the strength of a piece by as much as a
third--see Pioneer Pottery by Cardew for data.
Regards,
John
On Dec 17, 2007, at 2:23 PM, Keba M Hitzeman wrote:
> I found some information on crazing in the archives, but does a
> food-safe
> glaze that crazes make that piece not food safe?
John Hesselberth
www.frogpondpottery.com
"Man is a tool-using animal....without tools he is nothing, with
tools he is all" .... Thomas Carlyle
Vince Pitelka on mon 17 dec 07
I couldn't even guess the number of times that this has come up on
Clayart. Crazed glazes pose no toxicity risks, other than the risk of
increasing release of harmful glaze materials from an unstable glaze that
is already toxic, in which case it shouldn't be used on food-contact
surfaces anyway. Crazing reduces durability, because it has been proven
that craze cracks can extend through the glaze and the clay-glaze
interface.
Again, crazed glazes pose no toxic risks, even on lowfire wares. There i=
s
no evidence that evil bacteria grow in the craze lines and then
contaminant subsequent food. Most glazed lowfire ware is crazed, and
millions of people worldwide eat off such wares every day. There is no
record of anyone ever having contracted food poisoning from crazed
pottery.
It is wise to avoid and eliminate crazing whenever possible in order to
produce a better product. Uncrazed glazes can achieve proper glaze
compression, producing wares that are far more durable.
- Vince
--=20
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
vpitelka@dtccom.net
http://iweb.tntech.edu/wpitelka/
Steve Slatin on tue 18 dec 07
Keba --
Since you're a newcomer, there are things about ClayArt that
should be explained.
1. Many people who post regularly here have soapboxes. Once
they're on their soapbox, there's no stopping them, and they
might not tell you anything that's relevant, or accurate.
2. No one should be convinced to do anything based on the
advice of a single poster.
3. The more frequently a person posts, the more probable
that they have 'soapbox issues.'
There are, in fact, people who post regularly on clayart who
recommend that you use clay bodies that don't vitrify and
glazes that don't seal and other glazes that leach potentially
dangerous materials, that you fire a kiln on a wood floor
and thumb your nose at the government and refuse to pay taxes.
Personally, I wouldn't recommend any of these things.
Sincerely -- Steve Slatin*
*Known soapbox issues -- testing glazes for stability, using
glaze calc software, and expressing results in molar concentration
vs. in the unity formula
Keba M Hitzeman wrote:
Since I'm working with pre-made glazes right now, could you explain or point
me to where I can find more information about adding copper? That sounds
very interesting!
Keba
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Keba M. Hitzeman
Spanish - www.keba.hitzeman.com
Ceramics - yellowroomarts.blogspot.com
Coffee - coffee@engima22.com
---------------------------------
Looking for last minute shopping deals? Find them fast with Yahoo! Search.
Edouard Bastarache Inc. on tue 18 dec 07
Vince,
thanks
Alimentary wares = wares for foodstuffs.
Gis la revido,
(A la revoyure)
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.orange.fr/smart2000/livres.htm
http://www.pshcanada.com/Toxicology.htm
http://www.ceramique.com/librairie/
http://www.flickr.com/photos/30058682@N00/
http://myblogsmesblogs.blogspot.com/
Keba M Hitzeman on tue 18 dec 07
I hate to think of what little buggies could survive the dishwasher and
microwave. I would prefer not to have the crazing, especially on the inside
of the pieces, but will try the "ink test" that was mentioned and see what
happens with that.
So to make sure I'm getting all of this straight - "food-safe" generally
refers to what's leaching out of the glaze, and the type of glaze/firing
temperature/type of clay can determine whether or not that "food-safe" glaze
crazes?
So much to learn...
Keba
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Paul Lewing
Sent: Monday, 17 December, 2007 23:04
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Does glaze crazing always equal not food safe?
On Dec 17, 2007, at 11:23 AM, Keba M Hitzeman wrote:
I found some information on crazing in the archives, but does a food-
safe
glaze that crazes make that piece not food safe?
One of the problems in answering your question is that there is no
set definition of "food-safe". As someone pointed out, it usually
refers to the ingredients of the glaze itself leaching into food. I
assume that what you are asking here is about whether the craze lines
will harbor bacteria. We've discussed this before, and the consensus
has been that it's better to avoid crazing if you can, but some
people think germs can live in there and then come out and hurt you,
and others do not. It was even reported once, I believe, that the
problem was so severe that enough food oils could accumulate to
flavor subsequent servings of food.
My opinion is that if we have germs in our dinnerware's glazes that
can survive the dishwasher and the microwave, we're in bigger trouble
than having crazed glazes. Some have said that you might be legally
liable if someone ate food off your crazed dinnerware and got sick.
Nonsense. The first question anyone would ask in that situation
would be "You ate WHAT FOOD off that plate?" It always amazes me
when people worry about the germs that might be lurking in those
cracks, but they will eat a hamburger or a salad off that plate
without a second thought. How many people have you heard of lately
who have died from eating tainted food? And have you ever heard of
anyone being made ill by germs harbored in glazes? Of course not.
Just my two cents worth.
Paul Lewing
www.paullewingtile.com
____________________________________________________________________________
__
Clayart members may send postings to: clayart@lsv.ceramics.org
You may look at the archives for the list, post messages, or change your
subscription settings here: http://www.acers.org/cic/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots2@visi.com
Keba M Hitzeman on tue 18 dec 07
Wow...thanks for all the opinions and information! I thought crazing had
been discussed before, but I obviously wasn't looking in the right spots in
the archives.
Lynn - these pieces were 104 red clay with grog, bisqued to cone 04, fired
to cone 05. I belive the absorption is around 10% or so at cone 05.
Keba
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Lynn Goodman
Porcelain Pottery
Sent: Monday, 17 December, 2007 19:11
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Does glaze crazing always equal not food safe?
On Dec 17, 2007, at 2:23 PM, Keba M Hitzeman wrote:
> I found some information on crazing in the archives, but does a
> food-safe
> glaze that crazes make that piece not food safe?
Hi Keba,
It depends on your clay: how much absorption does it have? You didn't
say what type of clay you're using and what temp you're firing at. I
wouldn't consider crazed glaze on earthenware to be food-safe EVER--
food oils and juices can be absorbed into the clay via crazed glaze
and ferment or grow bacteria. This could make you very sick! If you
are using stoneware and it is FULLY mature (hence, has little
absorption) it's probably ok as long as you are very careful about
cleaning. Look at the info for your clay to find out what its
absorption is at the temp you are firing at.
Lynn
Lynn Goodman
Fine Porcelain Pottery
Cell 347-526-9805
www.lynngoodmanporcelain.com
____________________________________________________________________________
__
Clayart members may send postings to: clayart@lsv.ceramics.org
You may look at the archives for the list, post messages, or change your
subscription settings here: http://www.acers.org/cic/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots2@visi.com
Lee Love on tue 18 dec 07
On 12/18/07, Keba M Hitzeman wrote:
> I hate to think of what little buggies could survive the dishwasher and
> microwave.
One way to deal with germ paranoia, is to put copper in your
crazing glazes. Copper is antiseptic and would get all those
boogieman germs that Howard Huges and his crowd would be afraid of.
I have a shino birdbath that turns the water inside algae
green in the summer. Next time I make one, I will put an oribe or
seiji nuka glaze on the inside to see if the copper will keep the
bloom down.
--
Lee in Mashiko, Japan
http://groups.google.com/group/ClayCraft
"Men are born ignorant, not stupid. They are made stupid by
education." -- Bertrand Russell
Lynn Goodman Porcelain Pottery on tue 18 dec 07
On Dec 18, 2007, at 6:51 AM, Keba M Hitzeman wrote:
> Wow...thanks for all the opinions and information! I thought
> crazing had
> been discussed before, but I obviously wasn't looking in the right
> spots in
> the archives.
>
> Lynn - these pieces were 104 red clay with grog, bisqued to cone
> 04, fired
> to cone 05. I belive the absorption is around 10% or so at cone 05.
>
> Keba
Hi Keba,
Thanks for the info. You should keep trying different commercial
glazes until you find one that fits-- your work will be more
beautiful and durable if you do.
I know I'm in the minority here, but I still wouldn't serve food in a
crazed earthenware piece. 10% is a lot of absorption; if all you were
serving was tea in a tea ceremony it would be safe (boiling water, no
sugar, milk, etc.), but that's not likely to be the case. If you sell
or give the pieces to non-potters, I'd explain that they have to be
thoroughly cleaned. Better safe than sorry!
Lynn
Lynn Goodman
Fine Porcelain Pottery
Cell 347-526-9805
www.lynngoodmanporcelain.com
Maurice Weitman on tue 18 dec 07
At 22:32 +0900 on 12/18/07, Lee Love wrote:
> One way to deal with germ paranoia, is to put copper in your
>crazing glazes. Copper is antiseptic and would get all those
>boogieman germs that Howard Huges and his crowd would be afraid of.
So you're suggesting that we should formulate our glazes so that they
leach copper to make the glazes be more food safe?
>"Men are born ignorant, not stupid. They are made stupid by
>education." -- Bertrand Russell
No comment.
Regards,
Maurice
Keba M Hitzeman on tue 18 dec 07
Since I'm working with pre-made glazes right now, could you explain or point
me to where I can find more information about adding copper? That sounds
very interesting!
Keba
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Keba M. Hitzeman
Spanish - www.keba.hitzeman.com
Ceramics - yellowroomarts.blogspot.com
Coffee - coffee@engima22.com
People sleep peaceably in their beds at night only because rough men stand
ready to do violence on their behalf.
George Orwell
<))><
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Lee Love
Sent: Tuesday, 18 December, 2007 08:32
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Does glaze crazing always equal not food safe?
On 12/18/07, Keba M Hitzeman wrote:
> I hate to think of what little buggies could survive the dishwasher and
> microwave.
One way to deal with germ paranoia, is to put copper in your
crazing glazes. Copper is antiseptic and would get all those
boogieman germs that Howard Huges and his crowd would be afraid of.
I have a shino birdbath that turns the water inside algae
green in the summer. Next time I make one, I will put an oribe or
seiji nuka glaze on the inside to see if the copper will keep the
bloom down.
--
Lee in Mashiko, Japan
http://groups.google.com/group/ClayCraft
"Men are born ignorant, not stupid. They are made stupid by
education." -- Bertrand Russell
____________________________________________________________________________
__
Clayart members may send postings to: clayart@lsv.ceramics.org
You may look at the archives for the list, post messages, or change your
subscription settings here: http://www.acers.org/cic/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots2@visi.com
Vince Pitelka on tue 18 dec 07
Lynn Goodman wrote:
> I know I'm in the minority here, but I still wouldn't serve food in a
> crazed earthenware piece. 10% is a lot of absorption; if all you were
> serving was tea in a tea ceremony it would be safe (boiling water, no
> sugar, milk, etc.), but that's not likely to be the case. If you sell
> or give the pieces to non-potters, I'd explain that they have to be
> thoroughly cleaned. Better safe than sorry!
Lynn -
I do appreciate trying to be as safe as possible, but in this case, such =
a
warning can be equated with "If you don't want to get in an accident, the=
n
don't ever drive or ride in a car." This discussion has occurred on
Clayart many times in the past, and so far, there is absolutely no
evidence that anyone has ever been sickened by eating food out of an
earthenware dish with a crazed glaze. It just hasn't happened. People
all over the world have been preparing, baking, serving, and eating food
in crazed earthenware pieces for over a thousand years, and if crazing
were a toxicity hazard, it would be well covered in the literature.
Just to repeat what has been stated, crazing seriously weakens a piece of
pottery, so with utilitarian ware it is just a matter of common sense to
eliminate crazing. But as John Hesselberth pointed out, it is impossible
to eliminate crazing in salt-fired wares, because of the high-sodium (and
thus high-expansion) glaze that is inherent in the process.
It is also very difficult to prevent crazing in many lowfire glazes, and
such glazes are very widely used on utilitarian ware.
- Vince
--=20
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
vpitelka@dtccom.net
http://iweb.tntech.edu/wpitelka/
Edouard Bastarache Inc. on tue 18 dec 07
Vince,
I am wondering, using a very powerfull
microscope,
how many so-called surface "flaws" would be seen,
on any type of alimentary wares; metallic, plastic
and
ceramic....
Gis la revido,
(A la revoyure)
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.orange.fr/smart2000/livres.htm
http://www.pshcanada.com/Toxicology.htm
http://www.ceramique.com/librairie/
http://www.flickr.com/photos/30058682@N00/
http://myblogsmesblogs.blogspot.com/
----- Original Message -----
From: "Vince Pitelka"
To:
Sent: Tuesday, December 18, 2007 2:04 PM
Subject: Re: Does glaze crazing always equal not
food safe?
Lynn Goodman wrote:
> I know I'm in the minority here, but I still
> wouldn't serve food in a
> crazed earthenware piece. 10% is a lot of
> absorption; if all you were
> serving was tea in a tea ceremony it would be
> safe (boiling water, no
> sugar, milk, etc.), but that's not likely to be
> the case. If you sell
> or give the pieces to non-potters, I'd explain
> that they have to be
> thoroughly cleaned. Better safe than sorry!
Lynn -
I do appreciate trying to be as safe as possible,
but in this case, such a
warning can be equated with "If you don't want to
get in an accident, then
don't ever drive or ride in a car." This
discussion has occurred on
Clayart many times in the past, and so far, there
is absolutely no
evidence that anyone has ever been sickened by
eating food out of an
earthenware dish with a crazed glaze. It just
hasn't happened. People
all over the world have been preparing, baking,
serving, and eating food
in crazed earthenware pieces for over a thousand
years, and if crazing
were a toxicity hazard, it would be well covered
in the literature.
Just to repeat what has been stated, crazing
seriously weakens a piece of
pottery, so with utilitarian ware it is just a
matter of common sense to
eliminate crazing. But as John Hesselberth
pointed out, it is impossible
to eliminate crazing in salt-fired wares, because
of the high-sodium (and
thus high-expansion) glaze that is inherent in the
process.
It is also very difficult to prevent crazing in
many lowfire glazes, and
such glazes are very widely used on utilitarian
ware.
- Vince
--
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
vpitelka@dtccom.net
http://iweb.tntech.edu/wpitelka/
______________________________________________________________________________
Clayart members may send postings to:
clayart@lsv.ceramics.org
You may look at the archives for the list, post
messages, or change your
subscription settings here:
http://www.acers.org/cic/clayart/
Moderator of the list is Mel Jacobson who may be
reached at melpots2@visi.com
--
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Checked by AVG Free Edition.
Version: 7.5.503 / Virus Database: 269.17.4/1188 -
Release Date: 2007-12-17 14:13
Lee Love on tue 18 dec 07
Hi Keba,
By "food safe", the manufacturer is saying it meets guidelines
for food safety, in that it doesn't have hazardous materials in the
ingredients.
They can't guarantee against crazing because that is
dependent upon the clay body you put the glaze on. If you like the
glaze, you might try and find out what claybody it was tested on.
--
Lee in Mashiko, Japan
http://groups.google.com/group/ClayCraft
"Men are born ignorant, not stupid. They are made stupid by
education." -- Bertrand Russell
Mike on tue 18 dec 07
I'd like to say 'absolutely not' but I'm sure there are some exceptions,
so I'll just say nearly always not. People say that the crazing harbors
critters. Other people say the crazing is interesting, and it is in fact
often a desirable decorative effect in a glaze (I'm one of them). Right
now I happen to live in a culture of crazed glaze pots and have never
heard of a health issue regarding crazed glazes as the culprit. 'Course,
myself and everyone I know washes their dishes with soap and hot water,
and dries thoroughly. Of course I suppose there's always going to be
some troglodyte out there who leaves food in a dish in the sink for
weeks just to see how stinky and fuzzy it'll get, then uses it and gets
sick. Who knows? Heck, what about all the unglazed Bizen pottery out
there? Even vitrified the body is so open that it soaks up water like
crazy. That's like crazing to the 10th power, but it doesn't stop any
one from using those wonderful pots. They just make sure to keep them clean.
Tea ceremony folk in particular value the crazing in a bowl. The tea
discoloration accentuating the crazing lines in a bowl resulting from
repeated use is more highly regarded than a new 'clean' bowl. Got more
'flavor' to it, so to speak.
All that aside, a good glaze fit does make for a stronger pot, but
that's got nothing to do with food safe.
Mike 'Give me crazing or give me death' Martino
Mike
in Taku, Japan
karatsupots.blogspot.com
www.karatsupots.com
Keba M Hitzeman ????????:
> I found some information on crazing in the archives, but does a food-safe
> glaze that crazes make that piece not food safe?
>
> I was rinsing out some pieces and as I dried them, they started "popping",
> for lack of a better word - it sounded almost like sleet hitting a window.
> I held them up to the light, and saw craze lines where the water had been.
> After they dried, I checked the pieces again, and the craze lines were gone.
>
> The bottle says "food safe" (it's Amaco's Crystaltex "caramel"), but now I'm
> second guessing...
>
> Thanks!
>
> Keba in Dayton OH
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
>
>
Vince Pitelka on tue 18 dec 07
Edouard wrote:
> I am wondering, using a very powerfull
> microscope,
> how many so-called surface "flaws" would be seen,
> on any type of alimentary wares; metallic, plastic
> and
> ceramic....
Edouard -
I am not sure what you mean by alimentary wares, but I think that we woul=
d
find a lot of deep (in microscopic magnification) cracks and cuts in many
of the wares and utensils we use in the kitchen every day. The big
UC-Davis study of wood versus plastic cutting boards was a good example
and a big wake-up call. Practically everyone (but not my wife and I!) ha=
d
thrown away their beautiful wood cutting boards in favor of the supposedl=
y
more sanitary plastic ones, when the study revealed that the cuts in
plastic cutting boards harbor far more bacteria than wood cutting boards,
and that the wood has natural anti-bacterial qualities. It turns out tha=
t
the wood cutting boards are far more hygenic. And of course, when you ar=
e
talking about the cuts left by a knife on a plastic cutting board, you ar=
e
talking about the grand canyon in comparison to the size of a crazing
crack in a glaze surface.
- Vince
--=20
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
vpitelka@dtccom.net
http://iweb.tntech.edu/wpitelka/
Taylor Hendrix on tue 18 dec 07
Eddy, my friend!
I have yet to find any quantified examination of craze line width and
itsrelationship to the dimensions of the more common problematic
bacteria that might make it onto our plates. Until then, I'm rather
skeptical of the notion that the seperations of glaze surfaces harbor
bacteria in any significantly larger number than say the outer most
glaze surface or the day old wash cloth.
On 12/18/07, Edouard Bastarache Inc. wrote:
> Vince,
>
> I am wondering, using a very powerfull
> microscope,
> how many so-called surface "flaws" would be seen,
> on any type of alimentary wares; metallic, plastic
> and
> ceramic....
>
>
>
> Gis la revido,
> (A la revoyure)
>
> Edouard Bastarache
> Spertesperantisto
>
> Sorel-Tracy
> Quebec
> http://www.sorel-tracy.qc.ca/~edouardb/Welcome.html
> http://perso.orange.fr/smart2000/livres.htm
> http://www.pshcanada.com/Toxicology.htm
> http://www.ceramique.com/librairie/
> http://www.flickr.com/photos/30058682@N00/
> http://myblogsmesblogs.blogspot.com/
>
>
>
> ----- Original Message -----
> From: "Vince Pitelka"
> To:
> Sent: Tuesday, December 18, 2007 2:04 PM
> Subject: Re: Does glaze crazing always equal not
> food safe?
>
>
> Lynn Goodman wrote:
> > I know I'm in the minority here, but I still
> > wouldn't serve food in a
> > crazed earthenware piece. 10% is a lot of
> > absorption; if all you were
> > serving was tea in a tea ceremony it would be
> > safe (boiling water, no
> > sugar, milk, etc.), but that's not likely to be
> > the case. If you sell
> > or give the pieces to non-potters, I'd explain
> > that they have to be
> > thoroughly cleaned. Better safe than sorry!
>
> Lynn -
> I do appreciate trying to be as safe as possible,
> but in this case, such a
> warning can be equated with "If you don't want to
> get in an accident, then
> don't ever drive or ride in a car." This
> discussion has occurred on
> Clayart many times in the past, and so far, there
> is absolutely no
> evidence that anyone has ever been sickened by
> eating food out of an
> earthenware dish with a crazed glaze. It just
> hasn't happened. People
> all over the world have been preparing, baking,
> serving, and eating food
> in crazed earthenware pieces for over a thousand
> years, and if crazing
> were a toxicity hazard, it would be well covered
> in the literature.
>
> Just to repeat what has been stated, crazing
> seriously weakens a piece of
> pottery, so with utilitarian ware it is just a
> matter of common sense to
> eliminate crazing. But as John Hesselberth
> pointed out, it is impossible
> to eliminate crazing in salt-fired wares, because
> of the high-sodium (and
> thus high-expansion) glaze that is inherent in the
> process.
>
> It is also very difficult to prevent crazing in
> many lowfire glazes, and
> such glazes are very widely used on utilitarian
> ware.
> - Vince
>
> --
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Technological University
> vpitelka@dtccom.net
> http://iweb.tntech.edu/wpitelka/
>
> ______________________________________________________________________________
> Clayart members may send postings to:
> clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post
> messages, or change your
> subscription settings here:
> http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be
> reached at melpots2@visi.com
>
>
>
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.503 / Virus Database: 269.17.4/1188 -
> Release Date: 2007-12-17 14:13
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
>
--
Taylor, in Rockport TX
http://wirerabbit.blogspot.com
http://wirerabbitpots.blogspot.com
http://www.flickr.com/photos/wirerabbit/
Lee Love on tue 18 dec 07
On 12/18/07, Mike wrote:
> All that aside, a good glaze fit does make for a stronger pot, but
> that's got nothing to do with food safe.
>
> Mike 'Give me crazing or give me death' Martino
Hi Mike,
I think it is very much like fear mongering about copper.
Everybody forgets that the original problem with copper was in lead
glazes, because it helped lead be released more easily.
Crazing is less desirable in earthenware, where the clay
body is not vitreous. Stoneware does not depend as much on the
glaze to be non-porous because the clay itself is non-porous.
But, as we know, raku is earthenware too. And it is often
crazed. But it functions perfectly well to serve whisked tea in.
You just need to know how to care for these pieces. We have a
responsibility to teach folks how to use our pottery.
--
Lee in Mashiko, Japan
http://groups.google.com/group/ClayCraft
"Men are born ignorant, not stupid. They are made stupid by
education." -- Bertrand Russell
David Berg on tue 18 dec 07
On Dec 18, 2007, at 6:51 AM, Keba M Hitzeman wrote:
> I hate to think of what little buggies could survive the dishwasher
> and
> microwave.
Part of what makes people get sick with so called food poisoning is
related to the "dose" of bacteria that they eat. It takes a fairly large
inoculum of bacteria to overcome the body's defenses and make
one sick.
The cracks in a crazed glaze most likely won't harbor enough bacteria
to do the job. But try eating hamburger meat that was not processed
properly and is teaming with bacteria and then was not cooked enough
and then there is plenty of bacteria to make one sick - regardless of
whether the glaze is crazed or not.
dtb
David Berg
dberg2@comcast.net
http://bergstoneware.com/
Steve Slatin on wed 19 dec 07
Keba -- dilution does sometimes help, as a thinner
coat will have a higher percentage of material migrating
from the clay to the glaze layer than a thicker layer will.
It doesn't change the glaze, though. If you want the
glaze to reliably fit, you have to either change the
glaze or your clay. (This is not a joke -- if you're not
heavily committed to a particular clay, check to
see if the supplier can recommend something that
WILL work with the glaze you have.) One might
as well solve their problems easily ...
Many glazes that craze do so because they are a
little on the low side in silica. If you are committed
to your clay, you might try a line blend adding just
a little silica -- say one to five percent, by weight,
compared to the dry weight of the glaze you're
trying to fix. You may see the crazing reduced or
even disappear. OTOH, you may see the glaze
stop melting properly.
There are glazes that craze for other reasons than
insufficient silica. This may be something that cannot
be readily fixed.
Best wishes -- Steve Slatin
Keba M Hitzeman wrote:
Would it be feasible to dilute the glaze to see if that keeps it from
crazing? I don't know if dilution changes any of the glaze properties, or
if it just makes it thinner.
Keba
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Keba M. Hitzeman
---------------------------------
Looking for last minute shopping deals? Find them fast with Yahoo! Search.
Lee Love on wed 19 dec 07
> Edouard wrote:
> > I am wondering, using a very powerfull
> > microscope,
> > how many so-called surface "flaws" would be seen,
> > on any type of alimentary wares; metallic, plastic
> > and
> > ceramic....
Edouard,
I have found, if you let pottery weather outside, almost all
non-mat glazes and many mat glazes will show tiny crazing.
I am guessing that most pots that don't show crazing are mat
glazes and most mat glazes we see are less stable than gloss glazes.
--
Lee in Mashiko, Japan
http://groups.google.com/group/ClayCraft
"Men are born ignorant, not stupid. They are made stupid by
education." -- Bertrand Russell
Lee Love on wed 19 dec 07
On 12/19/07, Taylor Hendrix wrote:
> bacteria in any significantly larger number than say the outer most
> glaze surface or the day old wash cloth.
It defies common sense, but tight, non-porous surfaces are not
necessarily more anti-bacterial than porous ones. For example,
wooden cutting boards are better than plastic.
The other interesting thing is that copper and alloys such
as bronze and brass are more anti-bacterial than stainless steel.
Emisis basins used to be made of copper and bronze but are now
replaced by stainless steel. Copper or brass door plates are
anti-bacterial and there has been suggestions that hospitals replace
their stainless steel ones with them.
--
Lee in Mashiko, Japan
http://groups.google.com/group/ClayCraft
"Men are born ignorant, not stupid. They are made stupid by
education." -- Bertrand Russell
pdp1@EARTHLINK.NET on wed 19 dec 07
Hi David, all...
Yes...
The concern really, would seem to me to be two fold -
One, of appropriate informaiton for use, and, appropriate use, of whatever
sort of utensile or 'Pot' or Bowl or whatever one may have or obtain,
whether Hand Made or not...
And, relinquishing the need for hysteria and rote allegiance to vague or
confused informaitons past, especially when these have been charged with
emotional pejoritive or negative spin.
Crazed Glazes would be fine for Coffee or Tea Cups, when one's aesthetic
inclinations enjoy that look.
Mine do, and I have never seen any reason for them not to.
Otherwise, Crazed Glaes would be best for non liquid things, such as 'dry'
Foods, such as Nuts in the Shell, Whole Fruits, or other things which will
neither leach nor impart nor absorb.
This seems pretty simple to me, as far as an easy understanding and
application of criteria...and, I would think should be within the
intellectual reach of almost everyone.
Far as I know, the whole issue of Bacteria being 'in' Crazes is moot
compared to
the Bacteria in most people's mouths, on their hands, on every Ketchup or
Mustard or Sugar or Salt Shaker or Pepper Shaker
'bottle' on every counter of every 'dennys' or other restuarant...anything
within fifty feet or more, or downwind, of most people's children, any
pre-school or
grammarschool or playschool
environment
"period"...doorknobs...washcloths...kitchencounters...handshakes, and
'medical' facility, subway
hand-rails, cat-litter-boxes, sidewalk spittle or 'lungers', 'oysters' and
so on, and on and remourselessly on.
For the Bacteria in Crazes to be meaningful, two things need to occur -
First, the item needs to have been used to store something immediately past
which can offer a
significant Bacteria kind, or other inimically disposed Organism kind, in
the first place, for the Crazes to
oblige or harbor them...and, for the Crazes to in fact be wide enough to
allow them.
Say, storing raw Chicken or raw Pork, with lots of raw 'juices'... raw
typical 'hamburger' from the store with lots of intestinal factory process
contents mixed in...fresh Rat or Mouse Poops from
Rodents known to carry various 'things', or some sort of Lab Grade
Samples of ohhhhhh, I dunno, maybe Western Equine Influena or Dengui Fever
or something...
Then, after tepid storage of whatever one has elected, for a couple days,
ideally with a neutral or even nutrative liquid medium which can support the
vigor and
motility of the Organisms, somehow, for them to manage the treck ( or to
even bother at all, to enter ) in-TO the
'cracks'...
One then dumps out whatever the stuff was one was storing pro-tem, and,
maybe sluices out the container for about half a second under a thin trickle
of tap
Water, and, puts in say a nice already cooled off Cream Gravy, or, maybe
some left over from the picnic 'Tuna Salad' from a coupld days ago, made
with lots of Mayonaise...or some fresh picked Pole Beans or String Beans (
you know, just to invite Mr. Botulism while we are at it ) or raw Pea Nuts
( Aspirgillosis vectors ) or something , and then stores IT at room
temperature... or better yet, at around Body Temperature, for a day or two,
or three. Then eat THAT without heating it enough...in fact, take a few
sloppy salivating bites from a Spoon, and leave the Spoon in it too...
Then, maybe, m---a---y---b---e, if one is realy un-lucky, and if enough
Organisms had got into the mood for replicating enough ( Barry White or
Montavani or other music could be tried, you never know what will encourage
or inspire them, ) one would tend to
get some meaningful discomfort ( or outright demise, ) from eating that
tepid Cream 'Gravy'...or 'Tuna Salad', or Tuna Salad with fresh String Beans
jammed in like spikes, or whatever, and
one can blame it on the 'Crazes'...or rather, on some 'Bacteria' the Crazes
had supposedly harbored.
Oye...
...sigh...
Lol....
&
Best wishes!
Of course,
Phil
l v
----- Original Message -----
From: "David Berg"
> On Dec 18, 2007, at 6:51 AM, Keba M Hitzeman wrote:
>
>> I hate to think of what little buggies could survive the dishwasher
>> and
>> microwave.
>
> Part of what makes people get sick with so called food poisoning is
> related to the "dose" of bacteria that they eat. It takes a fairly large
> inoculum of bacteria to overcome the body's defenses and make
> one sick.
>
> The cracks in a crazed glaze most likely won't harbor enough bacteria
> to do the job. But try eating hamburger meat that was not processed
> properly and is teaming with bacteria and then was not cooked enough
> and then there is plenty of bacteria to make one sick - regardless of
> whether the glaze is crazed or not.
> dtb
> David Berg
Keba M Hitzeman on wed 19 dec 07
Steve,
Yep, I've been here long enough to realize that we all have our soapboxes!
I do appreciate the depth of experience and the variety of methods that
everyone uses, though. I'm learning from all of you, even those I don't
agree with.
Although I am now wondering if adding the copper was a joke I missed. :)
Keba
(I haven't found my soapboxes yet, at least regarding clay...)
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Keba M. Hitzeman
Dayton OH
Spanish - www.keba.hitzeman.com
Ceramics - yellowroomarts.blogspot.com
Coffee - coffee@engima22.com
People sleep peaceably in their beds at night only because rough men stand
ready to do violence on their behalf.
George Orwell
<))><
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Steve Slatin
Sent: Tuesday, 18 December, 2007 21:24
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Does glaze crazing always equal not food safe?
Keba --
Since you're a newcomer, there are things about ClayArt that
should be explained.
1. Many people who post regularly here have soapboxes. Once
they're on their soapbox, there's no stopping them, and they
might not tell you anything that's relevant, or accurate.
2. No one should be convinced to do anything based on the
advice of a single poster.
3. The more frequently a person posts, the more probable
that they have 'soapbox issues.'
There are, in fact, people who post regularly on clayart who
recommend that you use clay bodies that don't vitrify and
glazes that don't seal and other glazes that leach potentially
dangerous materials, that you fire a kiln on a wood floor
and thumb your nose at the government and refuse to pay taxes.
Personally, I wouldn't recommend any of these things.
Sincerely -- Steve Slatin*
*Known soapbox issues -- testing glazes for stability, using
glaze calc software, and expressing results in molar concentration
vs. in the unity formula
Keba M Hitzeman wrote:
Since I'm working with pre-made glazes right now, could you explain or
point
me to where I can find more information about adding copper? That sounds
very interesting!
Keba
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Keba M. Hitzeman
Spanish - www.keba.hitzeman.com
Ceramics - yellowroomarts.blogspot.com
Coffee - coffee@engima22.com
---------------------------------
Looking for last minute shopping deals? Find them fast with Yahoo! Search.
____________________________________________________________________________
__
Clayart members may send postings to: clayart@lsv.ceramics.org
You may look at the archives for the list, post messages, or change your
subscription settings here: http://www.acers.org/cic/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots2@visi.com
Tom at Hutchtel.net on wed 19 dec 07
Steve,
Great post. And as a 'soapboxer' myself, I agree. We all work from our
experience, and our interpretations of evidence vary greatly. Opinion is
the key word. Vince even told me once that the Minnesota Flattop was a
lousy kiln.
I think Mel ought to add your 1,2,3 items to the monthly "read this"
posting.
Tom Wirt
Hutchinson, MN
twirt@hutchtel.net
www.claycoyote.com
> Since you're a newcomer, there are things about ClayArt that
> should be explained.
>
> 1. Many people who post regularly here have soapboxes. Once
> they're on their soapbox, there's no stopping them, and they
> might not tell you anything that's relevant, or accurate.
>
> 2. No one should be convinced to do anything based on the
> advice of a single poster.
>
> 3. The more frequently a person posts, the more probable
> that they have 'soapbox issues.'
>
Vince Pitelka on wed 19 dec 07
Keba wrote:
> Yep, I've been here long enough to realize that we all have our soapbox=
es!
> I do appreciate the depth of experience and the variety of methods that
> everyone uses, though. I'm learning from all of you, even those I don'=
t
> agree with.
Keba -
I like your attitude. I may be well be one of the people Steve was
referring to in his little bit of "advice." It's fine if he wants to cal=
l
it a soapbox. I've had a passionate love affair with clay for almost 40
years now, and with that much experience it is natural that I have
developed some fairly strong opinions. One of my primary objectives as a
teacher is that I do not want anyone to be limited by unnecessary rules
and restrictions. It's a bit of a Libertarian attitude I suppose. In an
atmosphere of restrictive guidelines and rules, artistic creativity is
either stifled or it goes underground. The latter can be a good thing in
the broad view of art history, but in this case, I just want there to
leave open as many options as possible for the development of one's work,
and to put it on a more realistic day-to-day level, one's income.
Irrational toxic scare rears its ugly head regularly on Clayart. When
there is a perceived risk, it is always better to go with the safer route=
,
but there needs to be some sort of sound evidence and information to back
up the choice. People who tend to go with the safer route every time
there is the faintest perception of danger never leave their homes. Then
again, don't 80% of all accidents occur in the home, so maybe they should
leave?
I do try to speak up when some sort of unreasonable toxic scare issue
comes along, and I try to hit it early. And I am persistent. So, I gues=
s
that's when I get out my soapbox and put on my "chief inspector" badge an=
d
don my cape. I do have a cape now. Gayle Bair gave me one.
- Vince
--=20
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
vpitelka@dtccom.net
http://iweb.tntech.edu/wpitelka/
Vince Pitelka on wed 19 dec 07
Tom Wirt wrote:
> Vince even told me once that the Minnesota Flattop was a lousy kiln.
Whoa. Hold on there Tom. It is true that I don't like the flat top
design. , I love the arch aesthetically and functionally. And there are
plenty of people who have posted online about failures and frustrations
with flat tops. But I never said it was a lousy kiln. So there.
- Vince
--=20
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
vpitelka@dtccom.net
http://iweb.tntech.edu/wpitelka/
Ron Roy on wed 19 dec 07
Hi Lynn,
Good for you for saying that - the more you try the better you will get at it.
I think many potters put up with crazing simply because they can't get rid
of it.
RR
>Hi Keba,
>
>Thanks for the info. You should keep trying different commercial
>glazes until you find one that fits-- your work will be more
>beautiful and durable if you do.
>
>I know I'm in the minority here, but I still wouldn't serve food in a
>crazed earthenware piece. 10% is a lot of absorption; if all you were
>serving was tea in a tea ceremony it would be safe (boiling water, no
>sugar, milk, etc.), but that's not likely to be the case. If you sell
>or give the pieces to non-potters, I'd explain that they have to be
>thoroughly cleaned. Better safe than sorry!
>
>Lynn
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Keba M Hitzeman on wed 19 dec 07
Would it be feasible to dilute the glaze to see if that keeps it from
crazing? I don't know if dilution changes any of the glaze properties, or
if it just makes it thinner.
Keba
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Keba M. Hitzeman
Dayton OH
Spanish - www.keba.hitzeman.com
Ceramics - yellowroomarts.blogspot.com
Coffee - coffee@engima22.com
People sleep peaceably in their beds at night only because rough men stand
ready to do violence on their behalf.
George Orwell
<))><
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ron Roy
Sent: Wednesday, 19 December, 2007 19:44
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Does glaze crazing always equal not food safe?
Hi Lynn,
Good for you for saying that - the more you try the better you will get at
it.
I think many potters put up with crazing simply because they can't get rid
of it.
RR
>Hi Keba,
>
>Thanks for the info. You should keep trying different commercial
>glazes until you find one that fits-- your work will be more
>beautiful and durable if you do.
>
>I know I'm in the minority here, but I still wouldn't serve food in a
>crazed earthenware piece. 10% is a lot of absorption; if all you were
>serving was tea in a tea ceremony it would be safe (boiling water, no
>sugar, milk, etc.), but that's not likely to be the case. If you sell
>or give the pieces to non-potters, I'd explain that they have to be
>thoroughly cleaned. Better safe than sorry!
>
>Lynn
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
____________________________________________________________________________
__
Clayart members may send postings to: clayart@lsv.ceramics.org
You may look at the archives for the list, post messages, or change your
subscription settings here: http://www.acers.org/cic/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots2@visi.com
Ivor and Olive Lewis on thu 20 dec 07
I had my earliest experience of Crazed Glaze round about 1942.
I borrowed the large open crock in which my Mother founded and kneaded =
her bread dough, a terra cotta dish with a yellow glaze on the interior =
walls. In it I fermented Elderberry juice, making what must have been a =
primitive Sambuca. After four days of fermentation I decanted and =
bottled the liquor, put in the corks and buried the bottles.=20
When I washed out the large basin the glaze came away in patches.
Thinking about this now I suspect the glaze was deeply crazed and that =
the clay contained a good proportion of lime. The acid from the fruit =
must have penetrated the crack then dissolved the lime.Gas from the =
fermentation must have created sufficient pressure to lift the glaze =
from its weak hold on the clay.
The wine in the bottles that survived was superb, at least to a ten year =
old and his pal. I think now that we were good candidates for Lead =
Poisoning had we consumed the lot.
Treat all things with moderation, including moderation.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Brian Crocker on thu 20 dec 07
To David Berg,
David does your name "Berg" originate from Upsala, Sweden ?
My reason for asking is that my Great Grandfather on my mothers side was
from there and I would like to find more about the name.
Kind regards,
Brian, slangivan@dodo.com.au
============================
----- Original Message -----
From: "David Berg"
To:
Sent: Wednesday, December 19, 2007 12:41 PM
Subject: Re: Does glaze crazing always equal not food safe?
> On Dec 18, 2007, at 6:51 AM, Keba M Hitzeman wrote:
>
>> I hate to think of what little buggies could survive the dishwasher
>> and
>> microwave.
>
> Part of what makes people get sick with so called food poisoning is
> related to the "dose" of bacteria that they eat. It takes a fairly large
> inoculum of bacteria to overcome the body's defenses and make
> one sick.
>
> The cracks in a crazed glaze most likely won't harbor enough bacteria
> to do the job. But try eating hamburger meat that was not processed
> properly and is teaming with bacteria and then was not cooked enough
> and then there is plenty of bacteria to make one sick - regardless of
> whether the glaze is crazed or not.
> dtb
> David Berg
> dberg2@comcast.net
> http://bergstoneware.com/
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
Bonnie Staffel on fri 21 dec 07
When I apply a clear glaze on my Cone 9 fired ox. Pots I thin it down to
skim milk consistency and then get no crazing. It fires to a beautiful =
satin
finish. However, in tests with the glaze thicker, it always crazed.
Bonnie Staffel
http://webpages.charter.net/bstaffel/
http://vasefinder.com/bstaffelgallery1.html
DVD Throwing with Coils and Slabs
DVD Introduction to Wheel Work
Charter Member Potters Council
John Sankey on sat 22 dec 07
"When I apply a clear glaze on my Cone 9 fired ox. Pots I thin it
down to skim milk consistency and then get no crazing. It fires
to a beautiful satin finish. However, in tests with the glaze
thicker, it always crazed."
The tensile strength of glazes is inversely proportional to
thickness according to those who have measured such things. Half
the thickness, other things being equal and the clay and bond
being strong enough, means a glaze can handle twice the expansion
mismatch.
--
Include 'Byrd' in the subject line of your reply
to get through my spam filter.
Jeanie Silver on sat 22 dec 07
Dear John Sankey
Thank you for that very clear explanation. I understand something that I've
observed for years without having a clue.....
Can you tell me if glaze thickness has any effect on the delayed crazing of
glazes over unvitrified clay bodies over time?
Thanks
Jeanie in Pennslyvania
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