Tim Dippold on tue 6 jul 99
Martin calm down i never said that all vegetarians have pernicious anemia
which is rare and you can buy b12 supplements and I would not worry about
cobalamine deficiency unless you have been malnourished for most of your
life (grew up in a third world country during an extended famine) and if you
have had meat of any sort in your life then your body has a store of cobalt
compounds that can last you a life time and its not as if you body 'burns'
b12 like a carbohydrate. and as i said in the update you can't absorb
cobalamine compounds from metallic cobalt or its various salts and
carbonates. Our body was not built with a system to obtain the more widely
availible forms of cobalt. The human body does not come with factory
availible options. Cobalt that goes into your body from a glaze should just
go back out again like 'yellow in beer' to be crude. Cobalamin is simply the
term for any biologically processed cobalt compound. Vitamin B12 is in that
group. Comparing the cobalamine that is used by plants to those used by
animals is like comparing gasoline to diesel or propane to natural gas
ethanol(drinkin' liquor) to metanol. Both come from the same basic substance
(hydrocarbons) but they cannot be used interchangeably. Our bodies and the
bodies of animals are like gasoline engines and we just siphon the gas out
of ther tank. B12 then comes through the animals us like the additives
premium high octane that that someone who siphons gas is to stingy to buy
but needs or their car wont make it home and is not bothered by stealing
from other people yet is courteous enogh to leave a couple gallons in the
tank (refering to the way we raise animals to ensure the perpetuation of
that species yet supply the market's need for meat; i go overboard with
analogies when trying to explain my thoughts).
To keep the discussion of cobalt toxicity open I would think that the
form of cobalt would indicate whether or not it is harmful. PURE METALLIC?
NITRATE? SULFATE? CHLORIDE? OXIDE? CARBONATE? SILICATE? ALUMINATE? BORATE?
PHOSPHATE? HYDROXIDE? FERROCYANIDE? Which food acid will combine with it on
the plate? What does it do with stomach acids? Of course aspirating it is a
very bad idea and can not be to good for you. Even things as benign as water
should not be inhaled. I wonder how many different forms of carbon will have
a corresponding MSDS sheet (including hydrocarbons and organic compounds).
Even chemicals like iron oxide can be fatally toxic (ingested) to very young
children. Although in defense of the Iron glazes that i love, if the glaze
is stable it won't leach and if it is below saturation. (roughly over 11%) I
use the copper saturated "Oribe" often but would never use it as a liner on
a bowl or plate that I use in my kitchen. If your glaze is sturdy enough to
survive the abuse that all funtional ceramic kitchenwares must put up with
(dishwashers, food acids, salts, water, detergents, steak knives, being
clanged around in the sink, any metal utensil, dinged against faucets, to
name just a few of the horrors that dishes go through) then you really dont
have anything to worry about and in fact most glazes out there are durable
enough to take the continuous bombardment of chemical and mechanical
attacks. And if it does leach a chemical use it on a vase as cut flowers
don't last long enough to be affected any way or any of the other ceramic
forms that we use every day but don't think about like the dish we put our
loose change, lost buttons, paper clips, old keys that don't fit in any
current locks and other little things that lie around but are sooooooo
insgnificant to even bother with. just because it isn't sturdy and
technically perfect doesn't mean it isnt beautiful. Use proper precautions
when handling the dry materials especially that nasty silica.
>From the miserable desert cesspool of debauchery and iniquity that is
Albuquerque Tim Dippold setewall@hotmail.com
Time to sign off and watch Natural Born Killers before I return it
>From: Martin Howard
>Reply-To: Ceramic Arts Discussion List
>To: CLAYART@LSV.UKY.EDU
>Subject: Re: IMPORTANT !The truth about Cobalt Toxicity! UPDATE
>Date: Sat, 26 Jun 1999 19:54:50 EDT
>
>----------------------------Original message----------------------------
>Tim Dippold writes that
>The only sources of cobalamine that can be processed by the body is red
>meat. However it is synthesised in laboratories with bacteria and yeast
>much in the way that insulin and drugs like penicillin are synthesised.
>Plants obtain cobalt from the soil and process it into cobalamin
>compounds. The average amount of cobalt found in most US soil from
>samples taken in a 1969 survey showed levels at about 30 to 50 parts per
>billion. not quite enough to indefinitely sustain large populations of
>ruminants (grazing mammals) but fortunately mother nature is a much
>better recycler and chemist than we could ever hope to be. Ruminants
>obtain their cobalt that plants have processed from the soil. The
>animals process the plant derived cobalamin compounds into forms that
>are used in animal metabolism where the compounds are distributed
>amongst the animals via the food chain. That is how we obtain our
>cobalt.
>=====================================================
>So, every vegetarian and vegan should be deficient in cobalamin? Proof
>of that is required if your statement is to stand. Do you have such
>proof? If not please retract.
>
>Otherwise, vegetarians and vegans should be positively advised to handle
>and eat off cobalt glazed ware to assimilate some of this lovely blue
>which their bodies lack and need.
>
>Martin Howard, vegetarian/vegan just having mixed bread for family and
>guests in a lovely cobalt blue Victorian crock.
>
>Webbs Cottage Pottery and Press
>Woolpits Road, Great Saling
>BRAINTREE
>Essex CM7 5DZ
>01371 850 423
>araneajo@gn.apc.org
_______________________________________________________________
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John Hesselberth on wed 7 jul 99
Tim Dippold wrote:
>If your glaze is sturdy enough to
>survive the abuse that all funtional ceramic kitchenwares must put up with
>(dishwashers, food acids, salts, water, detergents, steak knives, being
>clanged around in the sink, any metal utensil, dinged against faucets, to
>name just a few of the horrors that dishes go through) then you really dont
>have anything to worry about and in fact most glazes out there are durable
>enough to take the continuous bombardment of chemical and mechanical
>attacks.
Hi Tim,
I'd like to switch away from the issue of cobalt to the broader issue of
metals leaching from glazes and give you an example where there can be
problems: I have seem two different copper containing glazes that have
lasted months in a dishwasher with no changes. They pass the vinegar
soak test for several days with no visible change. Yet the standard
leaching test shows that 25-40 mg/l of copper comes out of them. And not
just once. This is not some surface phenomena which goes away after the
pot has been used a couple times. Repeated tests show the same thing.
It is well known in the literature that less than 10 mg/l of copper can
make food taste bitter. Are we in the food flavor modification business?
Well, I'm not. Nor am I in the nutritional supplement business. Do we
need to get down to the levels acceptable in drinking water to be "food
safe"? I don't know because I don't know how the leaching test relates
to what actually happens in a food contact situation. However I do think
Monona Rossol's challenge to us to get down to water levels is certainly
a useful provocation. And I also know that water standards are about the
only place where attempts have been made to figure out what safe levels
of contamination might be--and we are contaminating food when we sell
glazed pots that are unstable.
Further, I now have enough data to be sure that the normal dishwasher and
vinegar soak tests are not sensitive enough to predict leaching (as
measured in the standard ASTM test) in the 0-25 mg/l range. They
probably do predict leaching in the 100+ mg/l range. In between 25 and
100, I don't know. In a few more months I will have enough data to know
how the standard leaching test relates to what goes into real food
(tomato sauce, coffee, orange juice and milk among others).
To me it is a matter of good craftsmanship to have stable glazes on food
contact surfaces (whether or not there is a toxicity concern). With our
present level of understanding, testing the glazes in the standard
leaching test is the only way to know whether or not your glazes are
stable if you are concerned with keeping leaching levels anywhere close
to the allowable levels for drinking water. Limit formulas and other
rules of thumb simply don't allow you to predict this, nor do the
dishwasher and vinegar tests. I'm getting more and more data all the
time that support these statements.
I don't have any intention of trying to eliminate use of cobalt, copper,
manganese or most any other metals we potters currently use (well I do
have a thing about lead and cadmium and uranium, but I probably shouldn't
get started on that). I do want to learn how to incorporate them into
our work so that our glazes are stable and attractive. And to me, stable
means somewhere within a few times drinking water standards--maybe all
the way down to drinking water standards.
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"It is time for potters to claim their proper field. Pottery in its pure
form relies neither on sculptural additions nor on pictorial decorations.
but on the counterpoint of form, design, colour, texture and the quality
of the material, all directed to a function." Michael Cardew in "Pioneer
Pottery"
Craig Martell on wed 7 jul 99
-----Original Message-----
From: Tim Dippold
----------------------------Original message----------------------------
>then you really dont have anything to worry about and in fact most >glazes
out there are durable enough to take the continuous >bombardment of chemical
and mechanical
>attacks.
..................................................
Hello Tim:
In reference to the above statement, I would have to say that you can't
really know this to be true. What do you mean by most? 50% of all glazes
or is it more? Less? What temperature are you talking about? I appreciate
your time in sharing your views but broad generalizations such as in your
above statement bother me. I've worked with glazes at several temps for the
past 25yrs. I know how to calculate molecular formulas etc, ad nauseum and
I would never presume to make such a general statement. My feeling is that
glazes are durable within certain limits and should be tested for leaching
in order to get a quantitative detemination. There have been many glazes
used on functional pots that are not suitable and we need to keep examining
our glazes and the materials we use to increase our knowledge of what to use
and how much.
For the record, I use cobalt ox and carb in glazes and I'm not the least bit
paranoid about it and don't advocate paranoia. I do advocate learning and
increasing ones knowledge base.
regards, Craig Martell in Oregon
Ron Roy on sun 18 jul 99
Tim said - snip
"and in fact most glazes out there are durable
>enough to take the continuous bombardment of chemical and mechanical
>attacks. And if it does leach a chemical use it on a vase as cut flowers
>don't last long enough to be affected any way or any of the other ceramic
>forms that we use every day but don't think about like the dish we put our
>loose change, lost buttons, paper clips, old keys that don't fit in any
>current locks and other little things that lie around but are sooooooo
>insgnificant to even bother with. just because it isn't sturdy and
>technically perfect doesn't mean it isnt beautiful. Use proper precautions
>when handling the dry materials especially that nasty silica."
Hi Tim - thought your answer would be useful to the rest of us so am
sending this one to the list. I am wondering how you have determined that
most of the glazes we use are durable - or more to the point - how do you
determine which chemicals are leaching from which glazes and how much?
RR
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Earl Brunner on mon 19 jul 99
A problem with Tim's quote below, and one that I have to remeind my students
time and time again is that once a pot that you make leaves your posession, you
have no control what so ever how it will be used. No glaze that can leach
harmful chemicals should EVER be used on the inside surface of a container.
You haave no control, but you do have to potential liability for their misuse.
Ron Roy wrote:
> ----------------------------Original message----------------------------
> Tim said - snip
> "and in fact most glazes out there are durable
> >enough to take the continuous bombardment of chemical and mechanical
> >attacks. And if it does leach a chemical use it on a vase as cut flowers
> >don't last long enough to be affected any way or any of the other ceramic
> >forms that we use every day but don't think about like the dish we put our
> >loose change, lost buttons, paper clips, old keys that don't fit in any
> >current locks and other little things that lie around but are sooooooo
> >insgnificant to even bother with. just because it isn't sturdy and
> >technically perfect doesn't mean it isnt beautiful. Use proper precautions
> >when handling the dry materials especially that nasty silica."
>
> Hi Tim - thought your answer would be useful to the rest of us so am
> sending this one to the list. I am wondering how you have determined that
> most of the glazes we use are durable - or more to the point - how do you
> determine which chemicals are leaching from which glazes and how much?
>
> RR
>
> Ron Roy
> 93 Pegasus Trail
> Scarborough, Ontario
> Canada M1G 3N8
> Tel: 416-439-2621
> Fax: 416-438-7849
>
> Web page: http://digitalfire.com/education/people/ronroy.htm
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
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