Reed Bakken on sat 9 aug 03
I was checking out some sites that Helen gave us yesterday
and ran into one that made me wonder. Is lead bisillicate stable
in a glaze? The glaze in question is:
C/03 Oxidation
75 lead bisillicate
5 borax frit
10 potash spar
10 ball clay
5 flint
3 bentonite
Won't this glaze leach lead? I fire C/04 at school and would love
to have a good clear earthenware glaze, but I'm concerned for
the students and my health. I've tested some glazes with lead
bisillicate
and they showed lead when tested with a lead test kit. Any ideas?
Thanks
Reed Bakken,
"Clay's The Way"
Slip & Slurry Pottery
Oregon, Il. 61061
815-732-3367
sspottery@oglecom.com
Ababi on sun 10 aug 03
In some sites
In some books, even new ones, they give you recipes.
The fact that it is a written word does not make it safe.
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Reed Bakken
Sent: Saturday, August 09, 2003 6:30 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Lead Bisillicate is stable?
I was checking out some sites that Helen gave us yesterday
and ran into one that made me wonder. Is lead bisillicate stable
in a glaze? The glaze in question is:
C/03 Oxidation
75 lead bisillicate
5 borax frit
10 potash spar
10 ball clay
5 flint
3 bentonite
Won't this glaze leach lead? I fire C/04 at school and would love
to have a good clear earthenware glaze, but I'm concerned for
the students and my health. I've tested some glazes with lead
bisillicate
and they showed lead when tested with a lead test kit. Any ideas?
Thanks
Reed Bakken,
"Clay's The Way"
Slip & Slurry Pottery
Oregon, Il. 61061
815-732-3367
sspottery@oglecom.com
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Janet Kaiser on sun 10 aug 03
Lead bisillicate is the most unstable of all the fritted leads.
You have the proof already.
Enough said?
Sincerely
Janet Kaiser
*** IN REPLY TO THE FOLLOWING MAIL:
>I was checking out some sites that Helen gave us yesterday
>and ran into one that made me wonder. Is lead bisillicate stable
>in a glaze? The glaze in question is:
>
> C/03 Oxidation
>
> 75 lead bisillicate
> 5 borax frit
> 10 potash spar
> 10 ball clay
> 5 flint
> 3 bentonite
>
> Won't this glaze leach lead? I fire C/04 at school and would
love
>to have a good clear earthenware glaze, but I'm concerned for
>the students and my health. I've tested some glazes with lead
>bisillicate
>and they showed lead when tested with a lead test kit. Any
ideas?
*** THE MAIL FROM Reed Bakken ENDS HERE ***
*** top of page reply was sent by Janet Kaiser ***
The Chapel of Art - Capel Celfyddyd
8 Marine Crescent - Criccieth LL52 0EA
Wales - UK - http://www.the-coa.org.uk
Tel: (++44) 01766-523570
Home of The International Potters=92 Path
John Baymore on sun 10 aug 03
Is lead bisillicate stable
in a glaze? The glaze in question is:
C/03 Oxidation
75 lead bisillicate
5 borax frit
10 potash spar
10 ball clay
5 flint
3 bentonite
Won't this glaze leach lead? I fire C/04 at school and would love
to have a good clear earthenware glaze, but I'm concerned for
the students and my health. I've tested some glazes with lead
bisillicate and they showed lead when tested with a lead test kit. Any
ideas?
Hi.
Without actual testing.... couldn't tell for sure....but experience says
that the likely answer is....YES. Formulating and FIRING non-leaching le=
ad
glazes is one of the most technical things you can try. Even slight
variations in firing...... and all bets are off. So all sorts of testing=
programs would be in order and also very standardized procedures would ne=
ed
to be set up for all aspects of production. Exactly what is NOT likely t=
o
happen in a teaching situation .
Of FAR more concern than the leaching factor.... which is HUGE.... is the=
exposure of you and the kids to lead...... from handling the dry glaze
materials, from the dry glaze powder, from the dust that will get in the
room, from the fumes from the kiln, and so on.
Kids are a particularly sensitive population when it comes to lead
compounds. I am sure that you have seen all the brouhaha over lead paint=
in the media.
In the USA there are some pretty stringent laws pertaining to the use of
lead compounds. Introducing them anywhere there are employees (even if
they don't work in the ceramics field) brings some serious environmental
control and paperwork issues from OSHA. Lead is a real "hot button issue=
"
now....and rightly so, I think. If you openly and completely checked thi=
s
issue with your school administration and let them know what you are
proposing......... my guess is that they'd have two kittens and a cow.
BEFORE you pursue this further........ I'd strongly suggest you contact
Monona Rossol at ACTSNY@cs.com and ask her to send you her publications
about lead use in schools.
best,
.....................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086-5812 USA
JBaymore@compuserve.com
http://www.JohnBaymore.com
603-654-2752 (studio)
800-900-1110 (studio)
"Earth, Water, and Fire Noborigama Woodfiring Workshop: August 15-24,
2003"
karen gringhuis on sun 10 aug 03
Reed -
> I fire C/04 at school and would love to have a good
clear earthenware glaze.... Any ideas?<
Yeah - with lead, FUGEDABOUDIT!!
> but I'm concerned for the students and my health.<
You should be! Read "Get the Lead Out" on pg. 81 of
Cushing's HANDBOOK or same in Summer '93 issue of
Ceramics Monthly. Particularly in a student and/or
functional situation, NO LEAD NO HOW NO WAY PERIOD.
I don't low fire but there have got to be recipes out
there for C/04 glossy clears without lead. Your job is
to find them & list members surely will help. Search
the ClayArt archives, Chappell's book, other glaze
recipe books. HANDBOOK also has one recipe for a
Glossy Clear on pg. 104 as ff:
GLOSSY CLEAR 3
Frit 3195 73
Neph. Sye. 8
Gerstley borate* 5
Lithium carb. 4
Zinc ox. 2
EPK 6
Bentonite 2
total 100%
*sub Gillespie borate
>I was checking out some sites that Helen gave us
yesterday and ran into one that made me wonder.<
There's definitely stuff out there that you should
wonder about - with minimal cautions and in sources
that should know better.
>they showed lead when tested with a lead test kit.<
If you absolutely must use lead in your own work which
is in any way functional (& which is NOT fired at
school), FORGET the test kit and have it
PROFESSIONALLY tested.
=====
Karen Gringhuis
KG Pottery
Box 607 Alfred NY 14802
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John Hesselberth on sun 10 aug 03
Hi Reed,
The answer to your question is 'almost certainly' it will leach lead.
Your lead test kit confirmed that it does--it just didn't tell you how
much. In today's world no one should be using lead in any form in
glazes UNLESS they 1) really know what they are doing, 2) have access
to a good testing laboratory(s) (for monitoring the leaching from their
pots and/or the lead level in their body--even if they are a sculptural
potter they should do the latter), and 3) have the equipment in their
studio to be able to handle lead compounds safely. Probably not more
than 1 in 1000 studio potters meet those criteria--maybe not that many.
I certainly don't and would never consider using lead-based glazes.
Regards,
John
On Saturday, August 9, 2003, at 12:30 PM, Reed Bakken wrote:
>
> C/03 Oxidation
>
> 75 lead bisillicate
> 5 borax frit
> 10 potash spar
> 10 ball clay
> 5 flint
> 3 bentonite
>
> Won't this glaze leach lead? I fire C/04 at school and would love
> to have a good clear earthenware glaze, but I'm concerned for
> the students and my health. I've tested some glazes with lead
> bisillicate
> and they showed lead when tested with a lead test kit. Any ideas?
> Thanks
>
http://www.frogpondpottery.com
http://www.masteringglazes.com
Janet Kaiser on wed 13 aug 03
Correction! As Gwyn Ace in New Zealand has pointed out...
MONOsilicate is the most unstable lead frit... Sorry for the
misinformation... Must be this heat melting my brain...
Sincerely
Janet Kaiser
*** top of page reply was sent by Janet Kaiser ***
The Chapel of Art - Capel Celfyddyd
8 Marine Crescent - Criccieth LL52 0EA
Wales - UK - http://www.the-coa.org.uk
Tel: (++44) 01766-523570
Home of The International Potters=92 Path
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