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Definitions of Food Safe



 
 
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  #1  
Old September 11th 08, 07:16 PM posted to rec.crafts.pottery
Elaine Stutt
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Posts: 20
Default Definitions of Food Safe

I know we're not too active here but i'd be interested in your
definition of food safe and how you determine if a glaze or particular
piece of pottery is food safe. Anyone reading this in the next month
or so feel free to chime in.

Thanks,

Elaine
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  #2  
Old September 11th 08, 08:07 PM posted to rec.crafts.pottery
Phil Rowley[_2_]
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Posts: 1
Default Definitions of Food Safe

Elaine Stutt wrote:
I know we're not too active here but i'd be interested in your
definition of food safe and how you determine if a glaze or particular
piece of pottery is food safe. Anyone reading this in the next month
or so feel free to chime in.

Thanks,

Elaine


There are certainly legal standards set in both the European Union and
the USA which require tableware to pass extraction tests for both lead
and cadmium. I'm only familar with the EU position, and it's possible
that USA may also cover other elements.

The tests are based on the use of 4% acetic acid as the extraction
medium - the exact method to be used will be laid down in an EN or ASTM
standard, which will lay down the sample preparation, quantity of acid
to be used in terms of the type and volume / surface area of the plate /
bowl etc, as well as the extraction time and temperature.

Levels of heavy metals which have been extracted from the article into
the acetic acid are then determined using a suitably-sensitive analysis
method - general atomic absorption spectrophotometry or I|CP and the
result expressed generally in mg/litre or converted to mg/dm2 of surface
area. These can them be compared with the relevant legal limit.

As you can see, it's quite complicated and certainly not something which
can be carried out without a proper laboratory.

I have seen information on "spot test" kits which are sold in America
which rely on a colourimetric reaction of heavy metals with a
compplicated organic reagent normally known as dithizone. I very much
doubt the reliability of these test kits, as dithizone gives colours
with many heavy metals and other common ions block the colour formation.

Of course, if you intend to take this matter further, you should become
fully familiar with all the relevant legal requirements - for instance,
I believe that California has specific extra (different ?) requirements
as a result of Proposition 65.

Regards,

Phil
  #3  
Old September 12th 08, 01:21 AM posted to rec.crafts.pottery
dkat
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Posts: 14
Default Definitions of Food Safe

This to me is a question that is not easily to answered. John Hesselberth
and Ron Roy have touched on it in their book and conclude that rather than
talk about the issue in terms of "food safe" instead ""safe to use with food
provided the clay/glaze fit issues ... are also addressed" (not to put words
in their mouth but that the glaze does not shiver or craze (so it does not
would allow bacteria or mold to grow). Copper easily leaches out of glazes.
Their Spearmint has leaching of copper at 1.63mg/l. They treat this as a
glaze safe to use for functional ware but they do not call it food safe. I
highly recommend Mastering Cone 6 by Hesselberth and Roy if you do not have
it.

I use copper bowls to beat my egg whites. I most certainly get more copper
out of that than I would out of almost any copper glaze I have ever used
however if the glaze is leaching a great deal of copper you have to ask
yourself do you really want the taste of food tainted with metal whether it
is dangerous our not. And then there is the issue of the glaze itself
losing it's beauty. You want a stable glaze for safety, for function and
for beauty.

If you want to be ridged about it and error on the side of safely then you
would not use a glaze on the inside of any piece which could hold food that
has lead, cadmium, barium, cobalt, copper (heavy metals) in it and that fits
the clay perfectly. In other words a liner glaze of white, clear or
brown....

John and Ron suggest using EPA standards for water (note that cobalt, copper
and lithium are not listed by the EPA).

http://www.epa.gov/OGWDW/dwh/c-ioc/cadmium.html
http://www.epa.gov/OGWDW/dwh/c-ioc/chromium.html
http://www.epa.gov/OGWDW/dwh/c-ioc/copper.html
http://www.epa.gov/OGWDW/dwh/c-ioc/barium.html
http://www.epa.gov/OGWDW/dwh/c-ioc/selenium.html
http://www.epa.gov/OGWDW/dwh/c-ioc/lead.html

"Elaine Stutt" wrote in message
...
I know we're not too active here but i'd be interested in your
definition of food safe and how you determine if a glaze or particular
piece of pottery is food safe. Anyone reading this in the next month
or so feel free to chime in.

Thanks,

Elaine



  #4  
Old September 12th 08, 06:24 PM posted to rec.crafts.pottery
Lee In Mashiko, Japan
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Posts: 12
Default Definitions of Food Safe

On Sep 11, 7:21*pm, "dkat" wrote:


John and Ron suggest using EPA standards for water (note that cobalt, copper
and lithium are not listed by the EPA).


Copper is an essential nutrient that is become less available in our
modern food because it is being leached out of our soil by pesticides
and fertilizers. Amounts released by well made glazes are less than
dietary requirements.

The original concerns about copper was related to lead glazes
where poorly formulated copper glazes helps lead be more soluble.

In India, the switch from copper and brass water containers for
plastic is causing problems with water safety. Plastic contained
water depends upon sunlight to keep it from going foul.

--
Lee in Minneapolis.
  #5  
Old September 17th 08, 07:49 AM posted to rec.crafts.pottery
Elaine Stutt
external usenet poster
 
Posts: 20
Default Definitions of Food Safe

Thanks for the contributions thus far.

Do studio potters in California test their work? Would it be
only pieces with say Cobalt in the glaze, one piece per batch?

I find a there's a lot of truth and rumour about glaze safety.
I don't know if many studio potters test at all and how
many of those test with other than simple kits. I know some who
take a glaze from the glaze book mentioned above, a glaze with cobalt,
noted with a low leaching rate and then consider the glaze safe even
when a differant feldspar is used. I've known some who used
lemon juice to visually check for leaching.

I do find that potters are in some ways expected to have higher
standards than plastics. Now there is a big variance in
concern and knowledge about glazes. I know some ( one ) who are very
concerned about crazing and test pieces with repeated heating and
freezing. There is concern over crazing even if no toxic
materials are imvolved, as bacteria could grow in the cracks.
That's a lot of concern considering that many/most people store
food in plastic that is easily scratched and there's little
concern about build up of bacteria there. I've also noticed some
plastic companies warning about heating food in plastic storage
containers. But it's widely done and I havn't seen a recall of
plastic containers. Let's face it, if overheated the plastics
melt down. They are created by huge companies and the studio
potters are very small. Of course, a single potter is a lot
easier to sue than a big petrochemical corporation.

Do any of you know of rules of thumb for glazes e.g.: no more
than 5%, 3% copper; no more than 1% cobalt; toxic material
okay if under clear glaze. Do you know of any glaze myths?

Do you have categories of food safe such as: table safe, safe
for dry foods only, microwave safe, safe for storage of acid
items like salads?

( Safety for oven or microwave concerns the clay body as much or
more than the glaze.)

Are the big manufacturers of "good china" still using lead glazes?
( in factory conditions with safety confirmed by testing )

Still curious and welcoming imput,

Elaine
  #6  
Old September 22nd 08, 08:08 PM posted to rec.crafts.pottery
Dee Kat
external usenet poster
 
Posts: 6
Default Definitions of Food Safe


This is nice to know and I have read it before - I believe one of the issues
with copper in a glaze is that it is one of the ingredients that leaches
very readily so if you are not getting significant amounts of copper
leaching from your pots that have a high amount of copper in the glaze (4%)
then you can feel secure that the base glaze is stable. However, what is
'significant' The question being posed here is what are the limits of
leaching for a standard of 'food safe'. As I said I don't think there is
any consensus on what is 'food safe'.

I believe the only standards in this regard that you find listed in this
country (U.S.A.) are for Lead and Cadmium (if I did not mention that... bad
on my part).

If you leave a lemon slice on a pot overnight and the color changes, this is
not a good glaze to use period. It is not a matter of 'food safe' - it is a
matter of quality. Who wants a pot that you think of as lasting over life
times that is going to be ruined the first time it is used with an acid base
food. Who wants to drink their orange juice, lemonaid or margarita and have
it ruined by a metallic taste.

"Lee In Mashiko, Japan" wrote in message
...
On Sep 11, 7:21 pm, "dkat" wrote:


John and Ron suggest using EPA standards for water (note that cobalt,
copper
and lithium are not listed by the EPA).


Copper is an essential nutrient that is become less available in our
modern food because it is being leached out of our soil by pesticides
and fertilizers. Amounts released by well made glazes are less than
dietary requirements.

The original concerns about copper was related to lead glazes
where poorly formulated copper glazes helps lead be more soluble.

In India, the switch from copper and brass water containers for
plastic is causing problems with water safety. Plastic contained
water depends upon sunlight to keep it from going foul.

--
Lee in Minneapolis.



  #7  
Old September 22nd 08, 08:08 PM posted to rec.crafts.pottery
Dee Kat
external usenet poster
 
Posts: 6
Default Definitions of Food Safe


This is nice to know and I have read it before - I believe one of the issues
with copper in a glaze is that it is one of the ingredients that leaches
very readily so if you are not getting significant amounts of copper
leaching from your pots that have a high amount of copper in the glaze (4%)
then you can feel secure that the base glaze is stable. However, what is
'significant' The question being posed here is what are the limits of
leaching for a standard of 'food safe'. As I said I don't think there is
any consensus on what is 'food safe'.

I believe the only standards in this regard that you find listed in this
country (U.S.A.) are for Lead and Cadmium (if I did not mention that... bad
on my part).

If you leave a lemon slice on a pot overnight and the color changes, this is
not a good glaze to use period. It is not a matter of 'food safe' - it is a
matter of quality. Who wants a pot that you think of as lasting over life
times that is going to be ruined the first time it is used with an acid base
food. Who wants to drink their orange juice, lemonaid or margarita and have
it ruined by a metallic taste.

"Lee In Mashiko, Japan" wrote in message
...
On Sep 11, 7:21 pm, "dkat" wrote:


John and Ron suggest using EPA standards for water (note that cobalt,
copper
and lithium are not listed by the EPA).


Copper is an essential nutrient that is become less available in our
modern food because it is being leached out of our soil by pesticides
and fertilizers. Amounts released by well made glazes are less than
dietary requirements.

The original concerns about copper was related to lead glazes
where poorly formulated copper glazes helps lead be more soluble.

In India, the switch from copper and brass water containers for
plastic is causing problems with water safety. Plastic contained
water depends upon sunlight to keep it from going foul.

--
Lee in Minneapolis.



  #8  
Old September 22nd 08, 08:08 PM posted to rec.crafts.pottery
Dee Kat
external usenet poster
 
Posts: 6
Default Definitions of Food Safe


This is nice to know and I have read it before - I believe one of the issues
with copper in a glaze is that it is one of the ingredients that leaches
very readily so if you are not getting significant amounts of copper
leaching from your pots that have a high amount of copper in the glaze (4%)
then you can feel secure that the base glaze is stable. However, what is
'significant' The question being posed here is what are the limits of
leaching for a standard of 'food safe'. As I said I don't think there is
any consensus on what is 'food safe'.

I believe the only standards in this regard that you find listed in this
country (U.S.A.) are for Lead and Cadmium (if I did not mention that... bad
on my part).

If you leave a lemon slice on a pot overnight and the color changes, this is
not a good glaze to use period. It is not a matter of 'food safe' - it is a
matter of quality. Who wants a pot that you think of as lasting over life
times that is going to be ruined the first time it is used with an acid base
food. Who wants to drink their orange juice, lemonaid or margarita and have
it ruined by a metallic taste.

"Lee In Mashiko, Japan" wrote in message
...
On Sep 11, 7:21 pm, "dkat" wrote:


John and Ron suggest using EPA standards for water (note that cobalt,
copper
and lithium are not listed by the EPA).


Copper is an essential nutrient that is become less available in our
modern food because it is being leached out of our soil by pesticides
and fertilizers. Amounts released by well made glazes are less than
dietary requirements.

The original concerns about copper was related to lead glazes
where poorly formulated copper glazes helps lead be more soluble.

In India, the switch from copper and brass water containers for
plastic is causing problems with water safety. Plastic contained
water depends upon sunlight to keep it from going foul.

--
Lee in Minneapolis.



  #9  
Old September 23rd 08, 10:15 AM posted to rec.crafts.pottery
Elaine Stutt
external usenet poster
 
Posts: 20
Default Definitions of Food Safe

"Dee Kat" ) writes:
This is nice to know and I have read it before - I believe one of the issues
with copper in a glaze is that it is one of the ingredients that leaches
very readily so if you are not getting significant amounts of copper
leaching from your pots that have a high amount of copper in the glaze (4%)
then you can feel secure that the base glaze is stable. However, what is
'significant' The question being posed here is what are the limits of
leaching for a standard of 'food safe'. As I said I don't think there is
any consensus on what is 'food safe'.


Yes, I've gotten that impression.

I believe the only standards in this regard that you find listed in this
country (U.S.A.) are for Lead and Cadmium (if I did not mention that... bad
on my part).

If you leave a lemon slice on a pot overnight and the color changes, this is
not a good glaze to use period. It is not a matter of 'food safe' - it is a
matter of quality. Who wants a pot that you think of as lasting over life
times that is going to be ruined the first time it is used with an acid base
food. Who wants to drink their orange juice, lemonaid or margarita and have
it ruined by a metallic taste.


Yes. And glass and ceramic have an advantage, in smell alone if not
taste, over some plastic and metal mugs that I have. While low tech
that lemon slice text sure is handy.


"Lee In Mashiko, Japan" wrote in message
...
On Sep 11, 7:21 pm, "dkat" wrote:


John and Ron suggest using EPA standards for water (note that cobalt,
copper
and lithium are not listed by the EPA).


Copper is an essential nutrient that is become less available in our
modern food because it is being leached out of our soil by pesticides
and fertilizers. Amounts released by well made glazes are less than
dietary requirements.

The original concerns about copper was related to lead glazes
where poorly formulated copper glazes helps lead be more soluble.

In India, the switch from copper and brass water containers for
plastic is causing problems with water safety. Plastic contained
water depends upon sunlight to keep it from going foul.
--
Lee in Minneapolis.


At one time I used to leave a plastic glass by my bedside. I no longer
leave a glass out but I gather I used plastic for its unbreakability.
The water had a bad taste by - the morning? next evening? At first
I blamed the water supply but then I realized it was the plastic
"glass" itself that was flavouring the water. I've seen a lot of talk
recently about which plastics, identified by recycling number, are
safe to use for storage ( once emptied of their original contents).

I know a potter who went to Ghana with an aid agency. He found, that in
that area, unglazed eathernware was great for water storage. Water
loss due to porosity wasn't that great and the evaporation on the
pots' surface kept the water distincly cooler than air temperature.

Elaine
  #10  
Old September 24th 08, 01:22 AM posted to rec.crafts.pottery
dkat
external usenet poster
 
Posts: 14
Default Definitions of Food Safe


At one time I used to leave a plastic glass by my bedside. I no longer
leave a glass out but I gather I used plastic for its unbreakability.
The water had a bad taste by - the morning? next evening? At first
I blamed the water supply but then I realized it was the plastic
"glass" itself that was flavouring the water. I've seen a lot of talk
recently about which plastics, identified by recycling number, are
safe to use for storage ( once emptied of their original contents).

I know a potter who went to Ghana with an aid agency. He found, that in
that area, unglazed eathernware was great for water storage. Water
loss due to porosity wasn't that great and the evaporation on the
pots' surface kept the water distincly cooler than air temperature.

Elaine


We are having what I some times consider 'overkill' going on in our studio
over the issue of 'food safe' and material safety. Pinnell's Weathering
Bronze green, which to me is a wonderful glaze, was eliminated as a glaze we
could use because it became known as 'not food safe'. This is a glaze that
a great many potters firing at cone 6 (and higher) use. The environmental
safety crew took away our Nytal Talc because after ten years of lawsuits in
the state about this talc's safety with no conclusion someone in the
University's administration decided that this talc was the same as asbestos
(it isn't). I can tell you that this caused all sorts of havoc since the
replacement talc did not have the same chemical analysis as the Nytal and 5
of our 10 glazes changed not in a good way. Reformulating seems to have
worked for the most part but anytime the glaze misbehaves you wonder - does
it still need some tweaking?

I can't complain too loudly really because good things came from this. I
went from having to make up a glaze in a room where I had to dodge students
and worry about them being exposed to dust to having a room just for making
glazes that has a really good venting system. I can understand in a studio
situation where there are too many cooks and students to monitor, wanting to
limit glazes to only ones that are good for functional pottery but if you
take this to extremes you only have glazes that go from white (possibly
clear if you can find one that doesn't craze) to brown. If you try to have
glazes only meant for sculptures, you can tell everyone that "this glaze is
not food safe - only for sculptures!" and you can be guaranteed that someone
is going to ignore the warning, glaze a bunch of dinnerware with it, decide
they don't want it and then sell it at the next studio pottery sale. Having
glazes that are 'food safe' would be nice. The problem is that no one knows
what this is. The decisions about the glazes seem arbitrary and without any
rhyme or reason which of course makes people dissatisfied.

Oh! and P.S. I refuse to drink water out of the refrigerator water supply
anymore because it taste yucky and I think it is from the new plastic filter
it goes through. I would rather go without even good wine than drink it
from a plastic or paper container. I would rather have far, far less with
quality than otherwise. Less is more - and the older I get the more meaning
this has.

There I have had my rant. I must say though that I do miss the bliss of
ignorance some times.

Donna


 




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