Lili Krakowski on tue 1 jul 08
Kim writes (I edited):
" Here is my question. I have worked in four public art centers as well as
my own studio. In two out of the four public ones there were glaze/body fit
problems ... crazing. I was told and read that this usually leads to
leaching out of glaze ingredients into food stored or cooked in said pots.
Not only were students not told about this but the glaze ingredients were
not available so one could figure out what exactly might be leaching into
ones casserole of coffee.
...I warned all my students .... However, to the best of my knowledge, the
one center has never done anything about this ...The other place is fixing
the issue even as I type.
Am I just a paranoid alarmist? Shouldn't the one center limit the use of
clay bodies and glazes to ones that fit each other for students making ware
for food use?
In other centers where commercially produced glazes are use can we take the
label as it is printed that the glazes are safe when fired according to
directions? I am guessing that the answer will be "Test! Test! Test!" but
want to hear from all sides. I hope some of the commercial glaze makers are
reading this because I would like to hear from them too. Thanks.
Kim: You are a good person, a caring teacher, and an exemplary craftsperson.
And we love you. Your worries are real, accurate, and appropriate. So
there.
Crazing and leaching are not connected. I could make a non-crazing glaze
that leaches like heck. Crazing is caused by a misfit between the body and
the glaze. Leaching is caused by an instability WITHIN the glaze. A dress
might or might not fit you (crazing). Does not indicate it will/will not
run in the wash (leaching).
Crazing and leaching may "meet" if a glaze crazes because it is underfired.,
and the underfiring makes the glaze unstable so that it leaches. But they
are not connected.
In "Mastering the Art of Cone 6 Glazes" Ron/John discuss leaching and tests
for leaching extensively. So look that up.
Leaching is considered dangerous when dangerous materials are leached. This
is not some sort of tongue twister like "Peter Piper picked etc." Clearly:
if a material is dangerous it should not be allowed to get into food.
Leaching may get it into the food.
Crazing is considered dangerous or risky for food connected wares because
nasty bacteria may lurk in those teensy cracks....etc.
Now. I think no "Center" should be using glazes that craze on the bodies
they offer. Just like that. If they co-ordinate they bodies they use and
the glazes they use, crazing should not be an issue.
The commercial glazes that say "safe if fired according to directions" may
or may not be on target. If the "Center" is not good about proper
firing --i.e. that temp is reached-- if the tech or janitor or whoever turns
the kiln off early, and so on....iffy, iffy. Most glazes have a firing
range of 3 cones or so.
Now a word of comfort. There ARE glazes that do not contain toxic
materials. I know Monona Rossol's list is in the Archives, because I put it
there.
I do think that commercially made glazes sold to schools should meet all
safety requirements. Check out NASCO.
Good luck.
Lili Krakowski
Be of good courage
Vince Pitelka on wed 2 jul 08
Lili Krakowski wrote:
"Crazing is considered dangerous or risky for food connected wares because
nasty bacteria may lurk in those teensy cracks....etc."
Dear Lili -
You wrote "may" above, and I cannot categorically say that it could never
happen, but there is also no evidence that it ever has. People have been
preparing food in and eating food out of crazed vessels for almost two
millennium, and to my knowledge no one has ever identified a case where
bacteria growing in the craze cracks caused people to get sick. As I said
in my post to Kim, it seems that it just doesn't happen.
I know that your opinions on such matters always stress extra safety, and
that is generally a very good thing, but in this case, if we stop eating
food from crazed vessels, we will stop eating food from a good percentage of
the glazed ceramic vessels out there. Remember that all salt-glazed wares
are crazed, and people have been drinking and eating food out of those
vessels throughout the modern studio pottery era with no noticeable
undesirable effect on the users.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Larry Kruzan on wed 2 jul 08
I am going to step into this VERY softly since I highly respect all who are
posting on this subject. That caution said, a couple years ago I had access
to some good mid and high power microscopes that I used to examine a large
number of glaze samples.
All of the test tiles were glazes that are very common and considered "safe"
for food contact. Most of the samples showed no visible crazing and passed
most of the common leaching tests that we have readily available to us
potters.
Under the mid power scope three fourths of the test tiles had visible
grazing. Under the high power microscope every one of the test tiles were
"grazed". I would say that the crazing opened large enough cracks that
certain bacteria or virus could possibly infest.
Sorry I cannot list the glazes and the specifics of the microscopes but it
was a couple years ago and I just can't find the notes anymore.
Although I am concerned with producing the tightest food safe glazes I can
make, I came to realize that there only so much we can do. Soap and hot
water washing of dishware seems to take care of these problems.
Checked my kitchen cabinets just before I typed this - found some 12 year
old commercial dishes made by a well known factory - they are crazed - been
eating from them for 12 years and have never noticed the crazing. In fact, I
intend to eat breakfast from them again in the morning.
Larry Kruzan
Lost Creek Pottery
www.lostcreekpottery.com
Taylor Hendrix on wed 2 jul 08
Hey Vince,
Hope you are staying busy busy busy this summer.
Every time this subject of bacteria and crazed glaze comes up I want
to shout "Sounds good, but has anybody done the math?" I tried once
for an hour or so to find measurements for the average bacterium and
the average seperation across a craze line but couldn't. I've not
found anyone who has measured craze lines. How far open ARE those durn
craze lines anyway? To be cleaver, if we can see them they must be at
least wide enough to cause light to bend but how far apart is that?
How many bacteria dance on the edges of craze lines anyway?
Inquiring minds want to know.
Taylor, in Rockport TX who still listens to his mama and to Mama Lili
On Wed, Jul 2, 2008 at 11:44 AM, Vince Pitelka wrote:
... to my knowledge no one has ever identified a case where
> bacteria growing in the craze cracks caused people to get sick. As I said
> in my post to Kim, it seems that it just doesn't happen.
...
Heather Pedersen on wed 2 jul 08
Not to mention the complete lack of regulation regarding selling
crazed items to the public.
This tells me that the people who study these things and get paid to
be super safe, don't think it is a problem.
Regards,
Heather Pedersen
On 7/2/08, Vince Pitelka wrote:
> Lili Krakowski wrote:
> "Crazing is considered dangerous or risky for food connected wares because
> nasty bacteria may lurk in those teensy cracks....etc."
>
> Dear Lili -
> You wrote "may" above, and I cannot categorically say that it could never
> happen, but there is also no evidence that it ever has. People have been
> preparing food in and eating food out of crazed vessels for almost two
> millennium, and to my knowledge no one has ever identified a case where
> bacteria growing in the craze cracks caused people to get sick. As I said
> in my post to Kim, it seems that it just doesn't happen.
>
> I know that your opinions on such matters always stress extra safety, and
> that is generally a very good thing, but in this case, if we stop eating
> food from crazed vessels, we will stop eating food from a good percentage of
> the glazed ceramic vessels out there. Remember that all salt-glazed wares
> are crazed, and people have been drinking and eating food out of those
> vessels throughout the modern studio pottery era with no noticeable
> undesirable effect on the users.
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>
Vince Pitelka on thu 3 jul 08
Larry Kruzan wrote:
"Under the mid power scope three fourths of the test tiles had visible
crazing. Under the high power microscope every one of the test tiles were
"crazed". I would say that the crazing opened large enough cracks that
certain bacteria or virus could possibly infest.
Larry -
I know that you, like most others, are just trying to be as safe and
sensible as possible, and that is always a good thing. You point out that
the dishes in your cupboard are crazed and that you intend to keep using
them. The same is true with most of us. I eat off of beautiful Paul Herman
plates and dishes at home, and there are crazed areas on some of them. Your
last sentence above is certainly correct, but as I have mentioned in
previous messages, there is no evidence that anyone has ever been sickened
from bacteria or virus from eating off of crazed dishes. If it were a
common occurrence, it would have been proven to be a problem. Obviously it
has been investigated, because EVERYTHING of that type has been thoroughly
investigated, and there have never been any stories or warnings about the
dangers of bacteria growth in craze cracks.
As I said in a previous message, it is our professional responsibility to
use safe, stable glazes on food-contact surfaces, but it does appear that
crazing is not a problem, unless it is increasing the leaching of toxic
materials on an already unstable glaze. If a glaze is stable and does not
leach any materials, crazing is not going to make any difference.
It would be nice if we could all just accept the fact that there is no
danger from bacteria in craze cracks. This comes up again and again, and I
suppose that is inevitable since there is so much misinformation out there
and people so often overreact when it comes to even the remotest chance of
any sort of concern about toxicity. This one is not a problem.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Heather Pedersen on thu 3 jul 08
I would like to throw out a caveat on this issue: porosity and
crazing is not a problem, as long as your dishes are allowed to dry
out between uses.
Therefore, if you are trying to sell to a restaurant, or other retail
food establishment, which uses their dishes constantly throughout the
day, not giving the dishes time to fully dry out, then you start
seeing these issues bear fruit (or fungi).
Restaurants have certain requirements for absorption (generally that
there be none at all) for the eating surface of their table ware.
There are also tests that restaurant quality tableware must pass
regarding resistance to crazing over time.
This is why you will probably never see studio made ceramics in a restaurant.
Regards,
Heather Pedersen
"The commas will take over the world!"
Doric T. Jemison-Ball ll on thu 3 jul 08
Dear Vince;
Back in the days when I used to work in Health Care, we had a saying, "If
the germs knew as much about infection control as we do, they'd kill a lot
more of us!"
The point being that we sometimes think we know more than we actually do. A
case in point- a while back in California, the health department banned
wooden work counters in food preparation areas as a potential source of
bacterial infection. The argument was wood was porous and couldn't be
sterilized, both true statements. Wood was, however, being widely used as
countertops in restaurants, butcher shops, etc., and folks hadn't been
dropping like flies from bacterial infections. The preferred substitute was
the impervious hard plastic cutting surfaces that can be sterilized, which
in short order replaced all the wood. Surprise, surprise, there was a marked
increase in bacterial infections following this change. It turns out that
the basic structure of wood bursts the cell walls of the bacteria [killing
them] whereas the plastic doesn't. Needless to say, California has NOT gone
back to wood. But knowing this, you don't need to worry about replacing
those butcher block counters in your kitchen.
We do not live in a sterile environment, which is why we have an immune
system to protect us from the stuff out there that may be trying to get us.
Whether we're talking about crazed or uncrazed dishes or our own hands, the
same rule applies-frequent thorough washing is the best protection against
those pesky microbes.
Doric T.Jemison-Ball II
Gualala, CA
707-884-5067 Voice
818-606-6678 CELL
buffalo@bbs-la.com
"You can always cure the sausage that's too long"
Susan Gatherers
----- Original Message -----
From: "Vince Pitelka"
To:
Sent: Thursday, July 03, 2008 10:43 AM
Subject: Re: Crazing glaze vs. safett
Larry Kruzan wrote:
"Under the mid power scope three fourths of the test tiles had visible
crazing. Under the high power microscope every one of the test tiles were
"crazed". I would say that the crazing opened large enough cracks that
certain bacteria or virus could possibly infest.
It would be nice if we could all just accept the fact that there is no
danger from bacteria in craze cracks. This comes up again and again, and I
suppose that is inevitable since there is so much misinformation out there
and people so often overreact when it comes to even the remotest chance of
any sort of concern about toxicity. This one is not a problem.
- Vince
Vince Pitelka
Joan Klotz on thu 3 jul 08
Edouard is probably the person who can give precise answers here but
you should realize that we are munching down bacteria all the
time. Most bacteria are harmless, some even beneficial, and even
when you get to the pathogenic ones you need to swallow a whole lot -
something like a million or so before you get ill. Unless you are
autoclaving (or kilning?) your dishes, removing them with sterile
tongs and using them immediately they've got bacteria all over them
crazed or not.
Happy eating,
Joan Klotz,
Venice, CA.
At 03:39 PM 7/2/2008, you wrote:
>Every time this subject of bacteria and crazed glaze comes up I want
>to shout "Sounds good, but has anybody done the math?" I tried once
>for an hour or so to find measurements for the average bacterium and
>the average seperation across a craze line but couldn't...
>
>How many bacteria dance on the edges of craze lines anyway?
>
>Inquiring minds want to know.
>
>Taylor, in Rockport TX who still listens to his mama and to Mama Lili
Kate on thu 3 jul 08
I'd like to introduce myself before jumping into a thread - my name is
Kathy McCoy and I have been reading this list for about 18 months now -
and I think I finally know how to post!
I learned in school that crazing was a bad, unsafe thing. I really
didn't connect the dots until this thread. I have some lovely, naked
(unglazed) pots. So, if nasty things can get into the crazes on glazed
pots, they would get to the fired clay - where presumable they lurk and
loiter until ready to attack. So, I guess they just sit on top of my
unglazed pots, with no crazing hidey holes to lurk in. I must, when I
wash my unglazed ones I must be doing a pretty decent job - I don't
think I've killed anyone (none of my friends or relatives are missing or
sick). So maybe it's all just a matter of personal pride in making a pot
with a perfectly smooth, uncrazed glaze, like one without pinholes or
craters, unless one actually is looking for that effect.
Sadly, I have two mugs that came out of the kiln and are crazed (clear
liner glaze on inside and outside rim). Pity, although I know they are
safe, the crazing just spoils them for me.
Hope to get to know you all better
Kathy McCoy
Vince Pitelka wrote:
> Larry Kruzan wrote:
> "Under the mid power scope three fourths of the test tiles had visible
> crazing. Under the high power microscope every one of the test tiles were
> "crazed". I would say that the crazing opened large enough cracks that
> certain bacteria or virus could possibly infest.
>
> Larry -
> I know that you, like most others, are just trying to be as safe and
> sensible as possible, and that is always a good thing. You point out that
> the dishes in your cupboard are crazed and that you intend to keep using
> them. The same is true with most of us. I eat off of beautiful Paul Herman
> plates and dishes at home, and there are crazed areas on some of them. Your
> last sentence above is certainly correct, but as I have mentioned in
> previous messages, there is no evidence that anyone has ever been sickened
> from bacteria or virus from eating off of crazed dishes. If it were a
> common occurrence, it would have been proven to be a problem. Obviously it
> has been investigated, because EVERYTHING of that type has been thoroughly
> investigated, and there have never been any stories or warnings about the
> dangers of bacteria growth in craze cracks.
>
> As I said in a previous message, it is our professional responsibility to
> use safe, stable glazes on food-contact surfaces, but it does appear that
> crazing is not a problem, unless it is increasing the leaching of toxic
> materials on an already unstable glaze. If a glaze is stable and does not
> leach any materials, crazing is not going to make any difference.
>
> It would be nice if we could all just accept the fact that there is no
> danger from bacteria in craze cracks. This comes up again and again, and I
> suppose that is inevitable since there is so much misinformation out there
> and people so often overreact when it comes to even the remotest chance of
> any sort of concern about toxicity. This one is not a problem.
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>
>
>
>
Edouard Bastarache on fri 4 jul 08
Joan,
as I usually say "What ever tuns you on" after discussing
in a sterile manner health issues on Clayart.
Vince wrote an excellent post on the matter of crazing
glazes, and I do not have much to add.
Lee Love once told me that Japanese eat from crazed pots
and they happen to live very old, which is another proof of
the justness of Vince' opinion.
I am still curious what a powerful microscope would give
viewing the surface of those supposedly safe industrial
wares.
You know microbes are very small and, if the surface of
the industrial wares have microscopic holes and cracks,
they would also harbour microbes,,,,
Gis la revido
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
Canada
http://www.flickr.com/photos/30058682@N00/
http://pagesperso-orange.fr/smart2000/livres.htm
http://www.flickr.com/photos/potier/20321056/
http://myblogsmesblogs.blogspot.com/
----- Original Message -----
From: "Joan Klotz"
To:
Sent: Thursday, July 03, 2008 3:22 PM
Subject: Re: Crazing glaze vs. safett
> Edouard is probably the person who can give precise answers here but
> you should realize that we are munching down bacteria all the
> time. Most bacteria are harmless, some even beneficial, and even
> when you get to the pathogenic ones you need to swallow a whole lot -
> something like a million or so before you get ill. Unless you are
> autoclaving (or kilning?) your dishes, removing them with sterile
> tongs and using them immediately they've got bacteria all over them
> crazed or not.
>
> Happy eating,
>
> Joan Klotz,
> Venice, CA.
>
> At 03:39 PM 7/2/2008, you wrote:
>
>>Every time this subject of bacteria and crazed glaze comes up I want
>>to shout "Sounds good, but has anybody done the math?" I tried once
>>for an hour or so to find measurements for the average bacterium and
>>the average seperation across a craze line but couldn't...
>>
>>How many bacteria dance on the edges of craze lines anyway?
>>
>>Inquiring minds want to know.
>>
>>Taylor, in Rockport TX who still listens to his mama and to Mama Lili
>
--------------------------------------------------------------------------------
No virus found in this incoming message.
Checked by AVG.
Version: 8.0.134 / Virus Database: 270.4.5/1533 - Release Date: 2008-07-03
19:19
Dannon Rhudy on sat 5 jul 08
> It would be nice if we could all just accept the fact that there is no
> danger from bacteria in craze cracks. This comes up again and again, and
I
> suppose that is inevitable since there is so much misinformation out there
> and people so often overreact when it comes to even the remotest chance of
> any sort of concern about toxicity. .........
It would be even nicer if we could accept that life
is fraught with all kinds of dangers, and being alive
is NOT SAFE. The world is NOT SAFE.
But we can be sensible, use good judgement, and
not think the sky is falling if there is any imperfection
anywhere. Especially since it is likely that there is no
PERFECTION anywhere.
But on the whole life seems more interesting and exciting
than the alternative. Personally, I hope to continue on
in this unsafe, unsanitary world for some time to come.
Worrying about crazed plates/cups/bowls is not high
on my list of concerns. I make the best glazes I can,
and wash my dishes with reasonable care. For the rest -
I've got a lot to do.
Hope everyone had a great 4th of July. A day of particular
thoughtfulness, for those of us in the U.S.A.
Regards
Dannon Rhudy (I set off some probably unsafe fireworks,
ate a vanilla/strawberry/blueberry ice cream cone, laughed
long and late, and considered that I am fortunate indeed.
Because I am. But I'm not safe.)
Veena Raghavan on sun 6 jul 08
Dannon and all a late Happy 4th of July. As Dannon said, we are indeed
fortunate, but on that day had much to think about. Loved the unsafe fireworks,
vanilla/blueberry ice cream cone, and laughing long and late bit, but most of all,
loved your ending, considering yourself fortunate indeed because you are. But
you are not safe! Just loved it.
May I join you in not being safe?!. Thanks for that.
Veena
In a message dated 7/5/2008 8:17:36 PM Eastern Daylight Time,
dannon@CCRTC.COM writes:
>
> Dannon Rhudy (I set off some probably unsafe fireworks,
> ate a vanilla/strawberry/blueberry ice cream cone, laughed
> long and late, and considered that I am fortunate indeed.
> Because I am. But I'm not safe.)
VeenaRaghavan@cs.com
Ingeborg Foco on sun 6 jul 08
Life is very dangerous! So far no one has managed to get out alive!!
Ingeborg
thepottersworkshop.com
On Fri, Jul 4, 2008 at 3:27 PM, Edouard Bastarache <
edouardb@sorel-tracy.qc.ca> wrote:
> Joan,
>
> as I usually say "What ever tuns you on" after discussing
> in a sterile manner health issues on Clayart.
>
> Vince wrote an excellent post on the matter of crazing
> glazes, and I do not have much to add.
>
> Lee Love once told me that Japanese eat from crazed pots
> and they happen to live very old, which is another proof of
> the justness of Vince' opinion.
>
> I am still curious what a powerful microscope would give
> viewing the surface of those supposedly safe industrial
> wares.
>
> You know microbes are very small and, if the surface of
> the industrial wares have microscopic holes and cracks,
> they would also harbour microbes,,,,
>
>
> Gis la revido
>
> Edouard Bastarache
> Spertesperantisto
>
> Sorel-Tracy
> Quebec
> Canada
>
> http://www.flickr.com/photos/30058682@N00/
> http://pagesperso-orange.fr/smart2000/livres.htm
> http://www.flickr.com/photos/potier/20321056/
> http://myblogsmesblogs.blogspot.com/
> ----- Original Message -----
> From: "Joan Klotz"
> To:
> Sent: Thursday, July 03, 2008 3:22 PM
> Subject: Re: Crazing glaze vs. safett
>
>
> Edouard is probably the person who can give precise answers here but
>> you should realize that we are munching down bacteria all the
>> time. Most bacteria are harmless, some even beneficial, and even
>> when you get to the pathogenic ones you need to swallow a whole lot -
>> something like a million or so before you get ill. Unless you are
>> autoclaving (or kilning?) your dishes, removing them with sterile
>> tongs and using them immediately they've got bacteria all over them
>> crazed or not.
>>
>> Happy eating,
>>
>> Joan Klotz,
>> Venice, CA.
>>
>> At 03:39 PM 7/2/2008, you wrote:
>>
>> Every time this subject of bacteria and crazed glaze comes up I want
>>> to shout "Sounds good, but has anybody done the math?" I tried once
>>> for an hour or so to find measurements for the average bacterium and
>>> the average seperation across a craze line but couldn't...
>>>
>>> How many bacteria dance on the edges of craze lines anyway?
>>>
>>> Inquiring minds want to know.
>>>
>>> Taylor, in Rockport TX who still listens to his mama and to Mama Lili
>>>
>>
>>
>
>
> --------------------------------------------------------------------------------
>
>
>
> No virus found in this incoming message.
> Checked by AVG.
> Version: 8.0.134 / Virus Database: 270.4.5/1533 - Release Date: 2008-07-03
> 19:19
>
--
Sincerely,
Ingeborg
www.thepottersworkshop.com
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