ray bridewell on wed 24 jun 98
I use a cone 5 glaze that has a lead frit as a main ingredient. I have
tested the fired surface of the glaze with a lead tester kit and have
found no lead. I love this glaze but I am concerned about it being a
danger both in the raw state and on a finished piece. Does anyone out
there have any technical knowledge they could share?
When I say I want leaded coffee I want caffeine.
Ray
Craig Martell on thu 25 jun 98
>----------------------------Original message----------------------------
>I use a cone 5 glaze that has a lead frit as a main ingredient. I have
>tested the fired surface of the glaze with a lead tester kit and have
>found no lead. I love this glaze but I am concerned about it being a
>danger both in the raw state and on a finished piece. Does anyone out
>there have any technical knowledge they could share?
Hi:
Lead frits render the stuff safer to use in the raw state but in a fired
glaze, the lead doesn't know if it came from a frit or was added raw.
The total chemistry of a glaze tells the whole story. If there is enough
silica and alumina in the glaze and it is a bright, fused, not underfired
glaze, then it may be safe to use for food. The guy who taught me about
glaze chemistry had a general rule for lead which is: In the Seger formula
of the glaze there has to be 3 molecules of silica for every molecule of
lead for the glaze to be considered for functional use. This is a MINIMUM
requirement and the key word here is, considered. I would have the glaze
tested for lead leaching by an accredited lab before I turned any pots loose
for use. Actually, I have a tough time understanding why anyone would even
consider using ANY kind of lead in a glaze for food service pots. There are
many other materials you can use to make very good glazes at cone 5. I, for
sure, wouldn't want the liability.
regards, Craig Martell-Oregon
Edouard Bastarache on thu 25 jun 98
Hello Ray,
i found only one scientific abstract in N.I.O.S.H.T.I.C.(National
Institute
for Safety and Health's database),
a US database, saying that one leaded frit was leaching lead, among many
more articles dealing with
lead among workers and users.It is not certainly much for stating that
leaded
frits are dangerous.
If you did the proper testing to make sure there is no lead leaching from
your glaze,just forget about it.
The authors did not mention the name and the maker of the frit.
Frangoise Melville, in Ceramics Monthly a few months ago, wrote about a
spanish village where folk
potters stopped using white lead because govt. officials supplied them with
a leaded frit.Countries of
the Common Market are often ahead of us in occupational and environmental
medicine,so if they
agreed that a leaded frit was ok for their citizens i feel that your glaze
is safe, more specially if your testing was well done and the results
negative.
Enclosed is a copy of the abstract.
Later,
Edouard Bastarache M.D.(Occupational and environmental medicine)
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouard/
----------
> De : ray bridewell
> A : Multiple recipients of list CLAYART
> Objet : Lead Frits Safe?
> Date : 24 juin, 1998 16:05
>
> ----------------------------Original message----------------------------
> I use a cone 5 glaze that has a lead frit as a main ingredient. I have
> tested the fired surface of the glaze with a lead tester kit and have
> found no lead. I love this glaze but I am concerned about it being a
> danger both in the raw state and on a finished piece. Does anyone out
> there have any technical knowledge they could share?
>
> When I say I want leaded coffee I want caffeine.
> Ray
Rick Sherman on fri 26 jun 98
Here is some information on lead in glazes issue which may be helpful
to those who intend to make and/or sell functional pottery in
California. The laws in this state are much more stingent than the
national laws thanks to Proposition 65 passed in 1986. The limits and
conditions are as follows from the:
California Tableware Education and Enforcement Program
Standards:
Tableware Type: FDA/CA DHS CA Prop 65
Anything exceeding these Anything exceeding
levels can't be sold in these levels must
the USA carry a worning if
Sold in CA+
Flatware/Plates 3.0 ppm 0.226 ppm
Small Hollowware/Bowls 2.0 ppm 0.1 ppm
Large Hollowware/Serving Dishes 1.0 ppm 0.1 ppm
Cups or mugs 0.5 ppm 0.1 ppm
Large pitchers, jugs 0.5 ppm 0.1 ppm
For information, you can call the hotline and leave a message for more
information.
Information Line: 1-800-644-LEAD [5323]
The program is eventually going to have a website at Website:
http://www.childlead.com/tableware/twhome.html
It is not up and running yet.
+The warning required is a yellow triangle fired into the glaze or a
statement that it is not for food use fired into the glaze.
If you are unsure of your glazes, better get a test kit from your local
clay supplier or have them tested by a lab.
Rick Sherman
California Crafts Network
San Jose, CA USofA
sherman@ricochet.net
Monona Rossol on fri 26 jun 98
Dear Clayarters--
Sorry I've been so busy, but the lead frit thread is very timely.
Please read the Clay Times safety column called "The Frit Myth." It includes
quotes from deposition testimony of Dr. Stopford from one of the two
lawsuits against the major lead glaze manufacturers last year (Duncan, Mayco,
Amaco, and others), information from the Center for Disease Control's MMWR
on a case of lead poisoning from a non-toxic "lead free" glaze (it contained
an insoluble frit), and a study that showed no difference between uptake in
animals by ingestion and by inhalation between lead monosilicate, lead
bisilicate, and red lead.
Don't be behind the times. It is now very clear that fritting of lead does
not make it safe. The improvement in health in the British Pottery industry
in the late 1800 when fritting was introduced was probably due primarily to
the fact that wet cleaning, hand washing and ventilation were introduced
simultaneously.
Monona Rossol, industrial hygienist
Arts, Crafts and Theater Safety
181 Thompson St., # 23
New York NY 10012-2586 212/777-0062
http://www.caseweb.com/acts/
| |
|
