Lili Krakowski on wed 2 jul 08
Yesterday I explained in dulcet tones why I could not "recalculate" a lead
glaze that originated with John Kenny's book, published in 1976. I also
explained that the older books often include materials we have learned NOT
to use. Lead being just one of them.
Fine.
So the whole family of lead glazes, lead in its diverse forms, lead
silicates, frits are GONE!
And we look up and find OTHER low fired glazes.
Such as:
Karen Stevens's 04 Transparent.
Recipe Name: Karen Stevens 04 trans
55.6 Frit--Ferro 3134
23.8 Kaolin--EPK
20.6 Flint
.303 Na2O
.003 K2O
.002 MgO
.691 CaO
1.000 Total
.287 Al2O3
.604 B2O3
.003 Fe2O3
3.069 SiO2
A simple basic Calcium Borate glaze of which there are many. Add an
opacifier, it is white. Add more clay and it becomes suitable for higher
fire.
Here is [Emmanuel] Cooper's 11 (from "The Potter's Book of Glaze Recipes")
80 Frit--Ferro 3134
9 Ball Clay--Kentucky Stone
11 Zircopax
.315 Na2O
.003 K2O
.003 MgO
.68 CaO
1.000 Total
.043 Al2O3
.627 B2O3
.002 Fe2O3
1.85 SiO2
.
or
Cooper #22 Opalescent blue glaze
20 Spodumene--Gwalia
60 Frit--Ferro 3124
12 Ball Clay--Old Mine #4
8 Flint
3 Rutile
.186 Li2O
.224 Na2O
.022 K2O
.004 MgO
.563 CaO
.519 Al2O3
.427 B2O3
3.631 SiO2
.
He says this is opalescent, clear where thin, blue-white opalescent where
thick. .75% cobalt carbonate gives a rich mottled blue.
As the original inquirer mentioned turquoise, voici Cooper 28 Turquoise
50 Frit--Ferro 3134
35 Feldspar--Kona F4
5 Whiting
4 Kaolin--EPK
6 Flint
.319 Na2O
.047 K2O
.001 MgO
.633 CaO
.214 Al2O3
.433 B2O3
.001 Fe2O3
2.354 SiO2
To this he adds 1% copper oxide for a bright turquoise.
Harry Fraser in "Glazes for the Craft Potter" has this Lithium Alkaline Blue
54 Flint
30 Lithium Carbonate
10.5 Kaolin--EPK
2 Bentonite
3.5 Copper Carbonate
.925 Li2O
.002 Na2O
.001 K2O
.004 MgO
.068 CaO
.098 Al2O3
2.176 SiO2
And there is this glaze from Bonnie Staffel:
Honey Glaze -Frank Gaydos
30 Frit--Ferro 3124
26 Gerstley Borate--1999
20 Nepheline Syenite
10 Kaolin--EPK
10 Flint
4 Lithium Carbonate
8 Iron Oxide--Red
.172 Li2O
.238 Na2O
.04 K2O
.003 MgO
.548 CaO
.415 Al2O3
.496 B2O3
.002 Fe2O3
2.573 SiO2
Ok. Please pay attention. These glazes ALL originated somewhere. But they
are/may be modified, altered, by changes in materials. I have no idea what
"soda spar" Cooper's source used--I put down Kona #4. I used Gwalia
Spodumene for the recipe given here, but have NO idea what was used
originally, nor what a potter might have on hand. I used Zircopax when
Cooper says Zirconium Silicate. Are they identical, or just close? No real
idea.
I don't know whether these glazes craze or leach. Furthermore, as those
who read me on ClayArt know, I am very opposed to the use of lithium carb.
in group situations, where someone on lithium medication might be affected
by exposure to more lithium.
As you note, however, the Fraser recipe is boron free.
So. You can now start testing these glazes on the clay bodies you use, and
see how, by doing blends, or trying this or that, you can get the look you
want, and a good stable glaze to boot.
.
Lili Krakowski
Be of good courage
Bill Merrill on wed 2 jul 08
Lead can be safe in a glaze if it is in the correct relationship with
silica. There is a formula, "Mellors" ratio that if you have the glaze
formula, you can calculate if it's food safe or not. Lead frits could
also work in place of lead. Some of the more beautiful early English
pots used lead. Lead is volatile and can coat electric kilns walls. Irma
Starr from Kansas City makes beautiful pots similar to 17th century slip
ware. There is a book English by Lionel Cooper "English Slipware
Dishes" that may be of interest to those who like Slipware.=20
=20
A utube video
=20
http://www.youtube.com/watch?v=3DWBZ-6xOxIeE
=20
By Irma Starr is very good, short, but good. She has a DVD on slip ware
that may be purchased.
=20
Lead of course is dangerous and should only be used with great caution.=20
=20
Be Safe!!!=20
=20
=20
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Lili
Krakowski
Sent: Wednesday, July 02, 2008 11:57 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Recalculating lead glaze! The promised sequel!
=20
Yesterday I explained in dulcet tones why I could not "recalculate" a
lead
glaze that originated with John Kenny's book, published in 1976. I
also
explained that the older books often include materials we have learned
NOT
to use. Lead being just one of them.
=20
=20
Fine.
=20
So the whole family of lead glazes, lead in its diverse forms, lead
silicates, frits are GONE!
=20
And we look up and find OTHER low fired glazes.
=20
Such as:
=20
Karen Stevens's 04 Transparent.
=20
Recipe Name: Karen Stevens 04 trans
=20
55.6 Frit--Ferro 3134
23.8 Kaolin--EPK
20.6 Flint
=20
.303 Na2O
.003 K2O
.002 MgO
.691 CaO
1.000 Total
=20
.287 Al2O3
.604 B2O3
.003 Fe2O3
=20
3.069 SiO2
=20
A simple basic Calcium Borate glaze of which there are many. Add an
opacifier, it is white. Add more clay and it becomes suitable for
higher
fire.
=20
Here is [Emmanuel] Cooper's 11 (from "The Potter's Book of Glaze
Recipes")
=20
=20
80 Frit--Ferro 3134
9 Ball Clay--Kentucky Stone
11 Zircopax
=20
=20
=20
.315 Na2O
.003 K2O
.003 MgO
.68 CaO
1.000 Total
=20
.043 Al2O3
.627 B2O3
.002 Fe2O3
=20
1.85 SiO2
.
or
=20
Cooper #22 Opalescent blue glaze
=20
20 Spodumene--Gwalia
60 Frit--Ferro 3124
12 Ball Clay--Old Mine #4
8 Flint
3 Rutile
=20
=20
.186 Li2O
.224 Na2O
.022 K2O
.004 MgO
.563 CaO
.519 Al2O3
.427 B2O3
3.631 SiO2
.
=20
He says this is opalescent, clear where thin, blue-white opalescent
where
thick. .75% cobalt carbonate gives a rich mottled blue.
=20
As the original inquirer mentioned turquoise, voici Cooper 28 Turquoise
=20
=20
=20
50 Frit--Ferro 3134
35 Feldspar--Kona F4
5 Whiting
4 Kaolin--EPK
6 Flint
=20
.319 Na2O
.047 K2O
.001 MgO
.633 CaO
=20
=20
.214 Al2O3
.433 B2O3
.001 Fe2O3
=20
2.354 SiO2
=20
To this he adds 1% copper oxide for a bright turquoise.
=20
Harry Fraser in "Glazes for the Craft Potter" has this Lithium Alkaline
Blue
=20
=20
54 Flint
30 Lithium Carbonate
10.5 Kaolin--EPK
2 Bentonite
3.5 Copper Carbonate
=20
=20
.925 Li2O
.002 Na2O
.001 K2O
.004 MgO
.068 CaO
=20
=20
.098 Al2O3
2.176 SiO2
=20
And there is this glaze from Bonnie Staffel:
=20
Honey Glaze -Frank Gaydos
=20
30 Frit--Ferro 3124
26 Gerstley Borate--1999
20 Nepheline Syenite
10 Kaolin--EPK
10 Flint
4 Lithium Carbonate
=20
=20
8 Iron Oxide--Red
=20
=20
.172 Li2O
.238 Na2O
.04 K2O
.003 MgO
.548 CaO
=20
=20
.415 Al2O3
.496 B2O3
.002 Fe2O3
=20
2.573 SiO2
=20
=20
Ok. Please pay attention. These glazes ALL originated somewhere. But
they
are/may be modified, altered, by changes in materials. I have no idea
what
"soda spar" Cooper's source used--I put down Kona #4. I used Gwalia
Spodumene for the recipe given here, but have NO idea what was used
originally, nor what a potter might have on hand. I used Zircopax when
Cooper says Zirconium Silicate. Are they identical, or just close? No
real
idea.
=20
I don't know whether these glazes craze or leach. Furthermore, as
those
who read me on ClayArt know, I am very opposed to the use of lithium
carb.
in group situations, where someone on lithium medication might be
affected
by exposure to more lithium.
=20
As you note, however, the Fraser recipe is boron free.
=20
So. You can now start testing these glazes on the clay bodies you use,
and
see how, by doing blends, or trying this or that, you can get the look
you
want, and a good stable glaze to boot.
=20
=20
=20
=20
=20
=20
.
Lili Krakowski
=20
Be of good courage
Edouard Bastarache on thu 3 jul 08
A text by Denis Caraty aka Smart.conseil :
"Hi ED,
Lead frits are less and less used because of the regulations on heavy metals
in the finished wares, but I cannot remember having heard that they were
toxic for workers and that cases of intoxication had been described here
(The Gien Factory) as being caused from working with these frits.
Toxicity could depend on the stability of the vitreous matrix containing
lead, on the fineness
of crushed particles, on the pH of the water or of the glaze bath...
Generally if one uses the ratio of Thorpe (or Mellor) in a frit or a glaze,
one obtains a rather reliable indication on the risk of lead release
(solubility in acid solution) of the compound used.
Cordialement, Smart.
Smart.Conseil"
Gis la revido
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
Canada
http://www.flickr.com/photos/30058682@N00/
http://pagesperso-orange.fr/smart2000/livres.htm
http://www.flickr.com/photos/potier/20321056/
http://myblogsmesblogs.blogspot.com/
Doric T. Jemison-Ball ll on thu 3 jul 08
Lili:
Thanks for everything. I was afraid the answer would be THERE AIN'T NO
SUBSTITUTE FOR LEAD. I'll try these out and let you know what I come up
with. I was just hoping against the odds that there would be a way to
recapture what was one of my favorite glazes from long ago.
Doric T.Jemison-Ball II
Gualala, CA
707-884-5067 Voice
818-606-6678 CELL
buffalo@bbs-la.com
"You can always cure the sausage that's too long"
Susan Gatherers
----- Original Message -----
From: "Lili Krakowski"
To:
Sent: Wednesday, July 02, 2008 11:57 AM
Subject: Recalculating lead glaze! The promised sequel!
> Yesterday I explained in dulcet tones why I could not "recalculate" a lead
> glaze that originated with John Kenny's book, published in 1976. I also
> explained that the older books often include materials we have learned NOT
> to use. Lead being just one of them.
>
Ron Roy on tue 8 jul 08
This glaze has a low expansion rate - best to test it well on any of the
clays you use to see if it shivers or breaks ware. It should be stable if
it's well melted.
>Karen Stevens's 04 Transparent.
>
>Recipe Name: Karen Stevens 04 trans
>
>55.6 Frit--Ferro 3134
>23.8 Kaolin--EPK
>20.6 Flint
This one will craze on just about any clay body. I will also be unstable -
Just not enough alumina or silica.
>A simple basic Calcium Borate glaze of which there are many. Add an
>opacifier, it is white. Add more clay and it becomes suitable for higher
>fire.
>
>Here is [Emmanuel] Cooper's 11 (from "The Potter's Book of Glaze Recipes")
>
>
>80 Frit--Ferro 3134
>9 Ball Clay--Kentucky Stone
>11 Zircopax
This one looks like it will be stable but the expansion is low - try 10
spodumene and 10 G200 or Custer.
>Cooper #22 Opalescent blue glaze
>
>20 Spodumene--Gwalia
>60 Frit--Ferro 3124
>12 Ball Clay--Old Mine #4
>8 Flint
>3 Rutile
>He says this is opalescent, clear where thin, blue-white opalescent where
>thick. .75% cobalt carbonate gives a rich mottled blue.
This is probably not stable and will craze badly. Replacing the spar with
spodumene may stop the crazing but the silica will still be low. Move the
silica up to 16 for a grand total of 110 will help the stability but copper
will still leach out. Not recommended for a liner glaze with the copper in
it.
>As the original inquirer mentioned turquoise, voici Cooper 28 Turquoise
>
>
>
>50 Frit--Ferro 3134
>35 Feldspar--Kona F4
>5 Whiting
>4 Kaolin--EPK
>6 Flint
>To this he adds 1% copper oxide for a bright turquoise.
This I would charaterize as dangerous in any context. The solubility of
lithium carb will cause problems - the expansion is very low.
There is less than half the alumina needed for stability and barely enough
silica needed to prevent leaching.
It will change colour in use and release both lithium and copper into
acidic foods.
>Harry Fraser in "Glazes for the Craft Potter" has this Lithium Alkaline Blue
>
>
>54 Flint
>30 Lithium Carbonate
>10.5 Kaolin--EPK
>2 Bentonite
>3.5 Copper Carbonate
This one looks OK but has just enough silica to be barely stable - I would
try it without the lithium carb as everything improves without it.
>And there is this glaze from Bonnie Staffel:
>
> Honey Glaze -Frank Gaydos
>
>30 Frit--Ferro 3124
>26 Gerstley Borate--1999
>20 Nepheline Syenite
>10 Kaolin--EPK
>10 Flint
>4 Lithium Carbonate
>
>
> 8 Iron Oxide--Red
Ron Roy
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ron Roy on wed 9 jul 08
There is more to it than just the right amount of silica - alumina is
important and the right amount of melting. Copper should not be present
because it lowers the stability of all glazes.
Then there is the constant testing that must be done to ensure you are
within the law.
Best to stay away from lead - in any form.
RR
>Lead can be safe in a glaze if it is in the correct relationship with
>silica. There is a formula, "Mellors" ratio that if you have the glaze
>formula, you can calculate if it's food safe or not.
Ron Roy
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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