"Rafael Molina-Rodriguez (Rafael Molina-Rodriguez)" on fri 20 jun 97
Clayarters :
This post is prompted by a message I received privately regarding my remarks
about Susan Peterson.
My recent post regarding Susan Peterson's quote about lead from her book
"The Craft and Art of Clay" was in no way meant to be disrepectful of such a
highly regarded teacher/author/potter. I cited her distinguished teaching
career and prolific writing in my message. I was merely agreeing with Ron
Roy's comment about this one specific area. I certainly didn't mean to
disparage her whole career.
My ideas about the use of lead is divided into two areas, the classroom and
my own personal studio work. In my teaching career over the last eight
years I have never had any form of lead (oxide or bisilicate) in the
classroom. The health hazards are well known. I have never and will never
unwittingly expose someone to a hazardous material. The legal liability is
also a reason for eschewing it's use in the classroom ( it gives me great
pause every time I receive offers in my mail box at the college for
liability insurance for faculty).
In my own personal studio work I am interested in exploring glazes that
contain lead bisilicate in the ^ 03 range. As I've said in a previous post
the texture and colors like cobalt blue, iron amber, chrome yellow and
copper green from this lead bisilicate base are quite handsome. It' a
decision I've made with the knowledge of the possible health hazards. I do
use precautions when handling (i.e. NIOSH approved respirator, gloves, wet
cleanup) and will only use this glaze on decorative objects or on areas of
utilitarian objects that will not come in contact with food or beverage.
In my research, and in discussion with other potters, I've come across some
interesting information. It's my understanding that the symbol pb is from
the Latin plumbum ( the English word plumbing derived from this source). Is
it anecdotal or fact that the decline of the Roman Empire was due in part by
the use of lead glazed water system? The Greek molubdos: molybdenum. And as
a friend of mine asks, who is incidentally a former Leach apprentice, how
does one explain Michael Cardew's longevity (I believe he lived into his
eighties) in spite of the fact he ate off of lead glazed earthenware?
Rafael
rmr3431@dcccd.edu
Paul Lewing on sat 21 jun 97
Rafael,
I've heard that about the lead from lead water pipes causing the
decline of Roman civilization. I've also heard it attributed to
drinking wine out of lead goblets, which seems to me would be a lot
deadlier. Who knows if that really caused the downfall of their
civilization or not, but it's an interesting concept- dinnerware as
historical determiner.
Paul Lewing, Seattle
Still waiting for the lawn to dry out enough to mow- maybe by August.
Suzanne Wolfe on mon 23 jun 97
The Romans had far bigger problems with lead than simply water pipes or
eating utensils. It was used as a cooking ingredient! They sprinkled it
on food as a sweetener. Yum!
Roger Bourland on fri 8 jan 99
This poem came through on a poetry list that I receive each
day and I had to share it with my fellow potters as it speaks of the
melancholy of lost oxides.
Best,
Roger
TimesStudy in
White
Times<
friend, an artist, phoned me up and said,
What shall I do for flesh? And what for bone?
All has some white, and the best white is lead.
But lead gets in the flesh and in the bone,
And if you are a woman, in the child
You bear years hence, and I know, have read
That you may use titanium or zinc,
Not poisonous, but you may be reviled
Because you lack the seriousness bred
For art in men - or else how could you think
Of compromise in this. And I own
I've tried them both, but the best white is lead
For making up the colors bold and mild,
Conceiving still lifes, matching tone with tone
To reproduce the spectra of the dead.
And I have stood for hours at the sink
Scrubbing white from hands until they bled.
And still my hands are stained, and still I think -
O flesh and blood - but the best white is lead.
------------------------------------------------------------------------
0000,0000,FFFFA. E. Stallings
Poetry
Volume CLXXIII, Number 3
January 1999
Copyright ) 1999 by the Modern Poetry Association.
All rights reserved.
Reproduced by Poetry Daily with permission.
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Times
Randall Moody on fri 5 feb 99
Hello all. I am looking for the appropriate frit to replace white lead
in some of the old recipes I have I also would like to know which frit
replaces lead bisilicate and red lead. I have looked for this info in my
limited library of books and have not found the direct info. Thanks!
Yann Ferric on mon 1 apr 02
Hi :D
Just to say there's info on lead here:
http://www.potters.org/category024.htm
Take care!
Love and light,
CaffeineYann
_________________________________________________________________
Chat with friends online, try MSN Messenger: http://messenger.msn.com
Rikki Gill on sun 13 oct 02
A friend of mine who is a nurse-practitioner told me that her mother was a
high school art teacher. Her classes used low fire glazes, some of which
contained lead. The kilns fired, unvented, in her class room. She now has
Alzheimer-like symptoms, no longer recognizes her family, etc, but her
daughter thinks it is the lead that has done this. She is having her mother
tested for lead poisoning. Pretty scary. I never have used lead, but I
have used plenty of other hazardous materials. You all be careful out
there. Rikki in Berkeley on a cool morning.
Edouard Bastarache on sun 13 oct 02
For "state of the art" information on the toxicology of lead go to:
http://perso.wanadoo.fr/smart2000/plomb_lead.htm
or
http://digitalfire.com/education/toxicity/materialsafety.html
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
Bonnie Staffel on sat 7 jun 03
Dear Clayarters,
OOPS, please disregard the sirens. The TV was on in the other room. Guess
my hearing is going.
Regards, Bonnie Staffel
Bonnie Staffel on sat 7 jun 03
Hi Clayarters,
When I was visiting in China in the late 70's we visited a sculpture
"factory" set up to show the tourists how it was done, there were many girls
sitting at tables painting on a bright orange substance on the famous
reproduction sculptures of the warrior on the horse. These were the shiny
ones with the many colors dripping about eight inches tall. They used
brushes and their tea cups were beside them. Each sculpture was handled by
hand, no ware boards, orange dust was all over the floor and on the girls'
clothes. It was my opinion that it was red lead which was commonly used to
glaze low fire work. Each piece of sculpture was hand carried to shelving
across the room, and then each one was hand carried to the kiln. At the
time I was aghast at this practice, but from comments by our guide, life was
cheap and the workers were "used up." Same was true of the embroiderers who
did such detailed work on silk. They worked until they lost their eyesight.
At the time there was also a lot of construction going on in the towns but
very little machinery to assist. Women worked along side the men in their
lace blouses (a change from the blue uniforms of the Mao regime) busy
digging the ditches deep enough to place the new sewer systems. Only a
crane was there to place the cement tubes in the ground.
I am hopeful that these practices have changed over the years. I am sure
there have been Clayart visitors to China who were able to see things
differently in the more recent years. Rural potteries were not available to
tourists at that time, so they had mock up situations.
To me the most exciting experience was to see the excavated clay soldiers in
the huge arena. The restoration was perfectly done, with no patching
visible.
Regards, Bonnie Staffel of Charlevoix, where there are a lot of sirens
blowing on the main street. Wonder what has happened. Been going on for a
good ten minutes.
http://pws.chartermi.net/~bstaffel/
Bill Merrill on wed 7 oct 09
Lead was used in glazes for many years before lead was known to be =3D
dangerous in water pipes in Roman times and in glazes. Lead make =3D
beautiful low fire glazes and high fire glazes also. ICarlton Ball had =3D
what he called "Tizzie" glazes, they worked from low fire to high fire =3D
using one glaze at many tepereatures. There can be lead safe glazes. =3D
There is a formula called Mellors ratio that you can tell if a glaze is =3D
safe even with lead in it. The formula tells you the parts per million =3D
of lead and silica , which can make the glaze safe. I am not pushinh =3D
the use of lead, as it is a heavy meatal tal can be dangerous in a dry =3D
form, a wet form, the kiln vapors and in a fired glaze. I just wanted =3D
to let potters know about Mellors ratio and certainly don't expect or =3D
encourage potters to use lead.....Just a little information for you =3D
glaze chemistry calculator potters.
Steve Slatin on thu 8 oct 09
Bill and others --
Mellor's ratio is useful as a starting point for
formulating a relatively low-leaching lead-based
glaze, but it's not really a solution to the problem.
The ratio (expressed as the sum of moles of lead plus=3D20
moles of alumina divided by the moles of acidic oxides)
tended to show low leaching at .5 -- a useful rule
of thumb -- but it doesn't tell you how much leaching
you will have, and some glaze formulations, like
those with boron in them, will leach substantially
even if there is a Mellor's ratio of .5 exactly.
I don't know how widespread boron glazes were when
Mellor did his work (the turn of the last century)
but glaze chemistry is a tricky business -- and
since lead is fugative, using a lead glaze in a
kiln can transmit lead to non-lead glazes, and
all of that work getting to a Mellor's ratio of
0.5 ends up being wasted ...
Besides, why pass up the opportunity to tell
your clients that your ware is lead free, even
though the stuff sold at Sam's Club might not
be?
Steve Slatin --=3D20
--- On Wed, 10/7/09, Bill Merrill wrote:
There is a formula called Mellors ratio that
> you can tell if a glaze is safe even with lead in it.=3DA0
> The formula tells you the parts per million of lead and
> silica , which can make the glaze safe.=3DA0 I am not
> pushinh the use of lead, as it is a heavy meatal tal can be
> dangerous in a dry form, a wet form, the kiln vapors=3DA0
> and in a fired glaze.=3DA0 I just wanted to let potters
> know about Mellors ratio and certainly don't expect or
> encourage potters to use lead.....Just a little information
> for you glaze chemistry calculator potters.
> =3D0A=3D0A=3D0A
Edouard Bastarache on thu 8 oct 09
Hello all,
for all sorts of info on lead read this ::
http://pagesperso-orange.fr/smart2000/Pb%20legislations.htm
and
http://www.hc-sc.gc.ca/cps-spc/pubs/cons/lead-plomb/index-eng.php
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://edouardbastarache.blogspot.com/
http://substitutions.blogspot.com/
http://www.flickr.com/photos/30058682@N00/
http://albertpaintings.blogspot.com/
http://cerampeintures.blogspot.com/
----- Original Message -----
From: "Bill Merrill"
To:
Sent: Wednesday, October 07, 2009 10:47 PM
Subject: Lead
Lead was used in glazes for many years before lead was known to be dangerou=
s
in water pipes in Roman times and in glazes. Lead make beautiful low fire
glazes and high fire glazes also. ICarlton Ball had what he called "Tizzie=
"
glazes, they worked from low fire to high fire using one glaze at many
tepereatures. There can be lead safe glazes. There is a formula called
Mellors ratio that you can tell if a glaze is safe even with lead in it.
The formula tells you the parts per million of lead and silica , which can
make the glaze safe. I am not pushinh the use of lead, as it is a heavy
meatal tal can be dangerous in a dry form, a wet form, the kiln vapors and
in a fired glaze. I just wanted to let potters know about Mellors ratio an=
d
certainly don't expect or encourage potters to use lead.....Just a little
information for you glaze chemistry calculator potters.
Edouard Bastarache on thu 8 oct 09
Hello,
if you are to use lead,
use "high alumina" lead bisilicate.
It is the most stable lead compounds
that can be used in pottery
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://edouardbastarache.blogspot.com/
http://substitutions.blogspot.com/
http://www.flickr.com/photos/30058682@N00/
http://albertpaintings.blogspot.com/
http://cerampeintures.blogspot.com/
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