wayneinkeywest on fri 2 jan 04
In the book "The Potter's Palette", a lead glaze is=20
shown as one of the choices, with all the caveats=20
in place about having one's work tested for metal=20
leaching, etc.
Then, it gives the recipe for the glaze (containing=20
lead bisilicate) and underneath says "...If you do=20
not wish to use lead-based glaze, substitute=20
borax frit for the lead bisilicate"
Hamer and Hamer (under borax frit) say "If borax=20
frit is being prepared for use in a lead (low sol)=20
glaze it is never fritted with the lead oxide. Lead=20
silicate must be prepared separately from the=20
borax frit in order to render the lead oxide insoluble. =20
See low sol and double fritting."
Would someone with some glaze experience care=20
to comment? Is it really that easy, just throw a=20
different substance in for the lead and be done=20
with it? Somehow, I don't think so, but I don't=20
have enough experience with glazes yet to make=20
that determination.
I intend to stay well away from lead glazes, to be sure
but some of the colors in those glazes are marvelous.
Can one simply substitute borax frit for lead?
I know it sounds as if I am attempting to fire my
cake (to ^10) and eat it too, but now I'm getting confused.
None of my other books mentions such a simple
either / or solution to the lead problem.
Wayne Seidl
Paul Lewing on fri 2 jan 04
on 1/2/04 12:34 PM, wayneinkeywest at wayneinkeywest@BELLSOUTH.NET wrote:
> Can one simply substitute borax frit for lead?
> I know it sounds as if I am attempting to fire my
> cake (to ^10) and eat it too, but now I'm getting confused.
Probably not, Wayne. I've never tried it, but you have a very good point
there when you say that some of those lead glaze colors were marvelous.
When it comes to color, or to range of maturing temperatures, or in ability
to fit a wide range of clay bodies perfectly, there is absolutely nothing
like lead. In the lowfire range, it is the perfect glaze
ingredient.......except for this one SLIGHT problem. One of the biggest
problems in getting third-world potters to stop using lead is that their
lead-free (mostly boron) glazes just do not have the brilliance and "juice"
that their lead ones had, and their customers won't buy them.
On the other hand, at cone 10, you were never going to get that anyway.
Lead would be long gone at that temperature. ALL of it would have
volatilized.
Paul Lewing, Seattle
Stephani Stephenson on fri 2 jan 04
Wayne wrote:
In the book "The Potter's Palette", a lead glaze is
shown as one of the choices, with all the caveats
in place about having one's work tested for metal
leaching, etc.
Then, it gives the recipe for the glaze (containing
lead bisilicate) and underneath says "...If you do
not wish to use lead-based glaze, substitute
borax frit for the lead bisilicate"
Is it really that easy, just throw a
different substance in for the lead and be done
with it?
Wayne Seidl
Wayne,I never before noticed that statement in the Potter's Palette...
but this also brings up the question, do they mean borax frit or boron
frit??
Borax is a soluble material also containing sodium . In my experience
it definitely has
an alkaline glaze color response, differing in many many instances
from lead based color response
I am not familiar with a 'borax frit', per se, though frits such as
frit 3134
are fritted sources of boron and may be fritted sourses of borax as
well.
So this is puzzling to me too.
Boron based frits still steer more toward alkaline color response
than lead color response
even without the sodium found in borax, though ,no, I have never done a
straight substitution.
But I wonder what frit they refer to, and I wonder what else is
fritted into the 'borax ' frit mentioned in the book?
Often times boron is combined with lead and other elements into 'lead
borosillicate' frits
which are/were used in commercial tableware industry. But that is still
considered a lead frit too.
Boron is also combined with non lead fluxes such as sodium , calcium,
potassium in non lead frits.
But then these are the types of frits used in Potter's Palette,'non
lead' recipes. So their reference is not clear to me either.
I am no expert, but in my own tests there are certain colors,
especially with iron, and in warm part of the color palette, that I
have a great deal of
trouble achieving, or have not been able to achieve without the use of
lead or lead frits.
Yet, I too have decided not to use lead in the studio, for reasons
which have to do with hygiene, health and also the interior of my kiln.
Because the color response is one of the main differences I too wonder
about this statement , especially in the "Potter's Palette". Looking
forward to hearing what others have to say.
Stephani Stephenson
steph@alchemiestudio.com
iandol on sat 3 jan 04
Dear Wayne,
Rather a complex problem you pose.
It is necessary to understand that the direct substitution of a Borax =
frit for one of the Lead Silicates is done to achieve one single =
purpose. It ensures that you can have a low temperature melt. Borax =
compounds to not replicate the optical properties of a lead based glaze. =
Do Hamer or the author of "The Potter's Palette" explain this.
I presume the caveat relating to the manufacture of a frit which =
incorporates both Lead and Boron is the potential to create a compound =
such as Lead borate. This might be acid soluble. Lead Borate monohydrate =
is which seems to indicate there may be a reaction with water.
How good it would be if the statements made by authors were backed up =
with some definitive science.
Best regards,
Ivor Lewis. Redhill, South Australia
Ababi on sat 3 jan 04
Hello Wayne!
Because I joined the pottery life when lead was an "outlaw" it was not
so hard to manage without it. I could not tell you; like old timers how
great were the colors- therefore I could not miss them. Actually in the
first test I made in my studio, to glazes of a potter that used them and
passed away may years ago there was a marvels red glaze...
I had in mind.
It is hard to explain but try...
Still have it somehow, not a great believer to try and substitute such a
glaze, better to say such a glaze behavior like I do in may cases.
If you remember - we need 1 mol (1mole is even better if you own it...)
We need one mol of flux.
In the one software I have but do not use The Glaze Simulator I can know
the expansion surface tension as well as the viscosity, three numbers to
lain on them.
Back to the one mol:
This one mol can be created from different flux.
The one thing that is not clear to me is: Is the molecular weight of a
glaze in a given cone - for our story 06 glaze- with the same behavior,
will be the same? If not there is a problem.
Presume, our flux only glaze has one molecule I mol of flux as it should
be (I ignore the alumina and silica) - I will make it as a circle; it's
diameter will be 223.9 - the same as the molecular Wight of the lead.
Can I create a one mol recipe of flux in this diameter using other
oxides?
Hard to believe.
Can I live without lead?
Longer hopefully!
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://ababi.active.co.il
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of
wayneinkeywest
Sent: Friday, January 02, 2004 10:34 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Lead Glaze substitution question
In the book "The Potter's Palette", a lead glaze is
shown as one of the choices, with all the caveats
in place about having one's work tested for metal
leaching, etc.
Then, it gives the recipe for the glaze (containing
lead bisilicate) and underneath says "...If you do
not wish to use lead-based glaze, substitute
borax frit for the lead bisilicate"
Hamer and Hamer (under borax frit) say "If borax
frit is being prepared for use in a lead (low sol)
glaze it is never fritted with the lead oxide. Lead
silicate must be prepared separately from the
borax frit in order to render the lead oxide insoluble.
See low sol and double fritting."
Would someone with some glaze experience care
to comment? Is it really that easy, just throw a
different substance in for the lead and be done
with it? Somehow, I don't think so, but I don't
have enough experience with glazes yet to make
that determination.
I intend to stay well away from lead glazes, to be sure
but some of the colors in those glazes are marvelous.
Can one simply substitute borax frit for lead?
I know it sounds as if I am attempting to fire my
cake (to ^10) and eat it too, but now I'm getting confused.
None of my other books mentions such a simple
either / or solution to the lead problem.
Wayne Seidl
________________________________________________________________________
______
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Tony Hansen on sat 3 jan 04
We were selling this book at the Axner booth at
NCECA last year and two people asked about this.
The term \"borax frit\" is first of all far too general,
should it be one containing 1% boron or 50% boron?
There are hundreds of borax frits in North America.
It is far better to put the glaze into a chemistry
program and substitute 1 part PbO for 1 B2O3. Then
the source of boron does not matter. However boron
is not going to melt nearly as well as lead.
It is better to identify the mechanism of the glaze
(the colorants, opacifiers, variegators) and
transplant it into a boron base glaze that will be
sympathetic to the mechanism.
>-------8<--------
>Wayne wrote:
>In the book \"The Potter\'s Palette\", a lead glaze is
>shown as one of the choices,
>... it gives the recipe for the glaze (containing
>lead bisilicate) and underneath says \"...If you do
>not wish to use lead-based glaze, substitute
>borax frit for the lead bisilicate\"
>Is it really that easy, just throw a
>different substance in for the lead and be done
>with it?
-------
===============
Tony Hansen, http://digitalfire.com
Personal Contact Page: http://digitalfire.com/services/contact.php
Calculation/Database Software for Ceramic Industry
wayneinkeywest on sat 3 jan 04
Thank you Tony. I have no idea yet why that would be important (I don't
have the necessary knowledge yet) but I will print out this reply and tuck
it into the book for further experimentation when I can.
Wayne Seidl
> We were selling this book at the Axner booth at
> NCECA last year and two people asked about this.
> The term \"borax frit\" is first of all far too general,
> should it be one containing 1% boron or 50% boron?
>
> There are hundreds of borax frits in North America.
> It is far better to put the glaze into a chemistry
> program and substitute 1 part PbO for 1 B2O3. Then
> the source of boron does not matter. However boron
> is not going to melt nearly as well as lead.
>
> It is better to identify the mechanism of the glaze
> (the colorants, opacifiers, variegators) and
> transplant it into a boron base glaze that will be
> sympathetic to the mechanism.
>
> >-------8<--------
> >Wayne wrote:
> >In the book \"The Potter\'s Palette\", a lead glaze is
> >shown as one of the choices,
> >... it gives the recipe for the glaze (containing
> >lead bisilicate) and underneath says \"...If you do
> >not wish to use lead-based glaze, substitute
> >borax frit for the lead bisilicate\"
> >Is it really that easy, just throw a
> >different substance in for the lead and be done
> >with it?
> -------
> ===============
> Tony Hansen, http://digitalfire.com
> Personal Contact Page: http://digitalfire.com/services/contact.php
> Calculation/Database Software for Ceramic Industry
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
>
| |
|
