piedpotterhamelin@COMCAST.NET on thu 8 oct 09
Hi everyone;=3D20
The Romans spread the use of lead-glaze throughout Europe and it was/is a c=
=3D
omponent of many low and middle range glazes. Lead poisoning for the indust=
=3D
rial worker in the mid-18 th century led factories like Wedgwood to search =
=3D
out the use of tincal (borax from Tibet) and alkaline or alkaline/lead frit=
=3D
s in glazes. While the rural anglo-european technique practiced in colonial=
=3D
America was dusting a lead powder onto dampened wares, the industrial prac=
=3D
tice of dipping pottery into a slop glaze was done as we emerged as a new b=
=3D
orn country and as Staffordshire potters brought their knowledge when they =
=3D
=3DC2=3DA0came here looking =3DC2=3DA0for a new life . My research has led =
to sever=3D
al=3DC2=3DA0variations of =3DC2=3DA0lead slop glazes and newspaper accounts=
of lead=3D
-free glaze recipes as potters confronted increased demand for their wares =
=3D
after the Embargo Act was ratified and the marketplace rang with "Buy Ameri=
=3D
can, not imports".=3D20
As many of you know, I am a redware potter, historically known as an earthe=
=3D
n-potter. I am usually confronted with the assumption that these red clay p=
=3D
ots were the only lead-bearing glazes but that is not true. All wares, incl=
=3D
uding the black-wares, yellow-wares, white chinas and others fired in the l=
=3D
ow to mid ranges in the kilns would possess lead to some degree in the glaz=
=3D
e. I have always been humored with the=3DC2=3DA0historical adovacy of using=
=3DC2=3D
=3DA0 Salt Glazed Stoneware=3DC2=3DA0for pickling (as it is described in ma=
ny 18t=3D
h and 19th newspapers) that this is a "safe and wholesome" glaze but they f=
=3D
ail to note that it is an exterior applied surface glaze; the interior work=
=3D
ing surface of the pot would have what is called an "albany slip" but my=3D=
C2=3D
=3DA0research has=3DC2=3DA0shown that sometimes other local clays were subs=
titute=3D
d and feldspar (and I suspect lead) would be used as fluxes. There are some=
=3D
low fire earthen ware pots that have an almost albany slip like glaze that=
=3D
I suspect is a lead/clay glazing =3DC2=3DA0.=3D20
Potters roasting lead have suffered from parkinson like disorders, stomach =
=3D
cramps, lethargy and madness. I found in one early newspaper an account of =
=3D
a father taking and hiding his daughter away to protect her=3DC2=3DA0from h=
er=3D
=3DC2=3DA0husband,=3DC2=3DA0a potter who would beat his wife each time afte=
r roasti=3D
ng his glazing lead in an open frying pan.=3D20
The press also reported at this time of families taking ill or of younger c=
=3D
hildren dying from food absorption of lead. Preventing lead leaching was wr=
=3D
ongly advised as simply a matter=3DC2=3DA0boiling the pots in water or coat=
ing =3D
the pots with fat.=3D20
Lead is the flux of choice for fit, color response, melting range, gloss an=
=3D
d refraction. It=3DC2=3DA0makes a beautiful glaze and the industry made gre=
at s=3D
trides=3DC2=3DA0through the mid 18th and 19th centuries to reduce exposure =
.=3DC2=3D
=3DA0The =3DC2=3DA0use of lead =3DC2=3DA0continues today but under very con=
trolled co=3D
nditions=3DC2=3DA0 and repeated fired ware testing that are not economicall=
y fe=3D
asible for most studio potters. The 1980's brought federal and state attent=
=3D
ion to lead-release across the consumer spectrum. During the Reagan years, =
=3D
the FDA concerned with lead exposure, cautioned against eating vegetables g=
=3D
rown within ten miles of any major roadway (lead deposited from gasoline fu=
=3D
mes emitted by vehicles) and the lead-free plumbing solder was put into bui=
=3D
lding codes. The FDA realized that the amount of lead tolerated by a grown =
=3D
adult was toxic to a child and the level of allowable lead release was cut =
=3D
in half. Again, this=3DC2=3DA0was in=3DC2=3DA0the 1980's, just 30 years ago=
. Massac=3D
husetts=3DC2=3DA0has a public interest group that advises that=3DC2=3DA0any=
glaze n=3D
ot be used=3DC2=3DA0until=3DC2=3DA0senior high.=3DC2=3DA0Barium by the way,=
was another=3D
glaze ingredie nt that was commonly used in amount up to 20 percent in a g=
=3D
laze, but is=3DC2=3DA0 now recognized to be safe in amount below 8 percent.=
Bar=3D
ium is rat poison, used as blood thinner (warfarin), an anticoagulant.=3D20
I am in still in disbelief that some British potters still use lead-frit an=
=3D
d post so on their websites. We know of the Mexican and Chinese pottery thr=
=3D
eat but fail to recognize our European risks.=3D20
I am currently involved in a compositional research project of redware pott=
=3D
ery shards that revealed a lead component for the bisqueware. Lead ore=3DC2=
=3D
=3DA0was mined =3DC2=3DA0in this area of an 19th century redware shop and h=
ypothe=3D
ses of lead fuming within the kiln and natural residual lead in the clay ar=
=3D
e being discussed.=3D20
I hope you enjoyed this and I would like to invite you to any of my talks a=
=3D
nd demonstrations;=3D20
www.piedpotter.com=3D20
Sincerely,=3D20
Rick Hamelin=3D20
The Pied Potter Hamelin=3D20
www.americanredware.com=3D20
Eric Hansen on fri 9 oct 09
I fail to understand the association between the safe use of modern lead
frit and the processes described in this post. Fritted lead does not equal
raw lead. No footnotes, no citations, merely assertions.p e a c e
h a n s e n
americanpotter@blogspot.com
hansencookbook@blogspot.com
thesuddenschool@blogspot.com
On Thu, Oct 8, 2009 at 8:52 AM, wrote:
> Hi everyone;
>
>
>
> The Romans spread the use of lead-glaze throughout Europe and it was/is a
> component of many low and middle range glazes. Lead poisoning for the
> industrial worker in the mid-18 th century led factories like Wedgwood to
> search out the use of tincal (borax from Tibet) and alkaline or
> alkaline/lead frits in glazes. While the rural anglo-european technique
> practiced in colonial America was dusting a lead powder onto dampened war=
es,
> the industrial practice of dipping pottery into a slop glaze was done as =
we
> emerged as a new born country and as Staffordshire potters brought their
> knowledge when they came here looking for a new life . My research has =
led
> to several variations of lead slop glazes and newspaper accounts of
> lead-free glaze recipes as potters confronted increased demand for their
> wares after the Embargo Act was ratified and the marketplace rang with "B=
uy
> American, not imports".
>
> As many of you know, I am a redware potter, historically known as an
> earthen-potter. I am usually confronted with the assumption that these re=
d
> clay pots were the only lead-bearing glazes but that is not true. All war=
es,
> including the black-wares, yellow-wares, white chinas and others fired in
> the low to mid ranges in the kilns would possess lead to some degree in t=
he
> glaze. I have always been humored with the historical adovacy of using S=
alt
> Glazed Stoneware for pickling (as it is described in many 18th and 19th
> newspapers) that this is a "safe and wholesome" glaze but they fail to no=
te
> that it is an exterior applied surface glaze; the interior working surfac=
e
> of the pot would have what is called an "albany slip" but my research
> has shown that sometimes other local clays were substituted and feldspar
> (and I suspect lead) would be used as fluxes. There are some low fire
> earthen ware pots that have an almost albany slip like glaze that I suspe=
ct
> is a lead/clay glazing .
>
> Potters roasting lead have suffered from parkinson like disorders, stomac=
h
> cramps, lethargy and madness. I found in one early newspaper an account o=
f a
> father taking and hiding his daughter away to protect her from
> her husband, a potter who would beat his wife each time after roasting hi=
s
> glazing lead in an open frying pan.
>
> The press also reported at this time of families taking ill or of younger
> children dying from food absorption of lead. Preventing lead leaching was
> wrongly advised as simply a matter boiling the pots in water or coating t=
he
> pots with fat.
>
> Lead is the flux of choice for fit, color response, melting range, gloss
> and refraction. It makes a beautiful glaze and the industry made great
> strides through the mid 18th and 19th centuries to reduce exposure . The
> use of lead continues today but under very controlled conditions and
> repeated fired ware testing that are not economically feasible for most
> studio potters. The 1980's brought federal and state attention to
> lead-release across the consumer spectrum. During the Reagan years, the F=
DA
> concerned with lead exposure, cautioned against eating vegetables grown
> within ten miles of any major roadway (lead deposited from gasoline fumes
> emitted by vehicles) and the lead-free plumbing solder was put into build=
ing
> codes. The FDA realized that the amount of lead tolerated by a grown adul=
t
> was toxic to a child and the level of allowable lead release was cut in
> half. Again, this was in the 1980's, just 30 years ago. Massachusetts has=
a
> public interest group that advises that any glaze not be used until senio=
r
> high. Barium by the way, was another glaze ingredie nt that was commonly
> used in amount up to 20 percent in a glaze, but is now recognized to be
> safe in amount below 8 percent. Barium is rat poison, used as blood thinn=
er
> (warfarin), an anticoagulant.
>
> I am in still in disbelief that some British potters still use lead-frit
> and post so on their websites. We know of the Mexican and Chinese pottery
> threat but fail to recognize our European risks.
>
> I am currently involved in a compositional research project of redware
> pottery shards that revealed a lead component for the bisqueware. Lead
> ore was mined in this area of an 19th century redware shop and hypothese=
s
> of lead fuming within the kiln and natural residual lead in the clay are
> being discussed.
>
> I hope you enjoyed this and I would like to invite you to any of my talks
> and demonstrations;
>
> www.piedpotter.com
>
> Sincerely,
>
> Rick Hamelin
>
> The Pied Potter Hamelin
>
> www.americanredware.com
>
Maggie Furtak on sat 10 oct 09
I'm currently reading "Brunelleschi's Dome," by Ross King. (Highly recomme=
nd it, by the way, as well as his book on the painting of the Sistine Chape=
l). In it the author notes that the dangers of lead had been suspected as =
far back as Roman times. Everyone had noticed that plumbers, who were in d=
aily contact with the stuff, always seemed to be pale, sickly-looking types=
.
Funny that we can know something is dangerous and still keep using it for s=
o long if it presents an otherwise easy solution to a problem. Makes me wo=
nder what is in common use currently that later generations will be horrifi=
ed about.
Off to the Farmers's Market!
Maggie
Pate Ceramics
pateceramics.etsy.com
pateceramics.blogspot.com
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