lili krakowski on tue 2 mar 10
Hi, Ron!
In the Dark Ages of Quimper and other lovely leadglazed faience we did =3D
not consider lead solubility, or crazing and like that as dangers to the =
=3D
user.
However now we know better--so my question is: CAN a c.04 and similar =3D
glaze ever be hard enough to resist modern detergents, dishwasher soaps, =
=3D
microwaving--not to mention the scratching by knives and forks. =3D20
Lili Krakowski
Be of good courage
James Freeman on tue 2 mar 10
And a related question, if you will: How many washings and eatings of
acidic foods does it take until all of the free and leachable lead is
leached and gone? In other words, can I eat off of an antique lead-glazed
dish safe in the knowledge that my forebears have unwittingly taken the
bullet for me, having through use already eaten all of the lead there was t=
o
eat? It seems that if there is a finite quantity of lead in the glaze,
there must also be a point where, through use and washing, there is no free
lead remaining.
...James
James Freeman
"All I say is by way of discourse, and nothing by way of advice. I should
not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/clayart/
On Tue, Mar 2, 2010 at 9:20 AM, lili krakowski wro=
te:
>
> In the Dark Ages of Quimper and other lovely leadglazed faience we did no=
t
> consider lead solubility, or crazing and like that as dangers to the user=
.
> However now we know better--so my question is: CAN a c.04 and similar gla=
ze
> ever be hard enough to resist modern detergents, dishwasher soaps,
> microwaving--not to mention the scratching by knives and forks.
>
Lee Love on tue 2 mar 10
On Tue, Mar 2, 2010 at 9:01 AM, James Freeman
wrote:
This is how we use a lead glazed Bowl, from the part of
Pakistan/Afganistan the Tailban Hangout at:
http://www.facebook.com/photo.php?pid=3D3D4111109&l=3D3D2fadb4c95a&id=3D3D5=
507270=3D
56
--=3D20
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
John Hesselberth on tue 2 mar 10
On Mar 2, 2010, at 10:01 AM, James Freeman wrote:
> And a related question, if you will: How many washings and eatings of
> acidic foods does it take until all of the free and leachable lead is
> leached and gone? In other words, can I eat off of an antique =3D
lead-glazed
> dish safe in the knowledge that my forebears have unwittingly taken =3D
the
> bullet for me, having through use already eaten all of the lead there =3D
was to
> eat? It seems that if there is a finite quantity of lead in the =3D
glaze,
> there must also be a point where, through use and washing, there is no =
=3D
free
> lead remaining.
Hi James,
A good question. I have no hard data, but from what I have seen you are =3D
not leaching out lead specifically. Rather you are dissolving a tiny bit =
=3D
of the surface of the glaze. I don't believe the bulk composition of the =
=3D
glaze changes. That would suggest as long as there is glaze present you =3D
will leach a tiny bit of lead with every exposure to acids.
You might get a quick test of this by using one of the hardware-store =3D
lead testing kits on a well-used lead glazed piece. Test a worn area and =
=3D
an area that is still largely intact and see if both test for the =3D
presence of lead.
Regards,
John=3D
Ron Roy on tue 2 mar 10
Hi Lili,
I think we can - it is more difficult because you have to get the
right amount of silica and alumina in the melt.
First step is to analyze the frits we have - find out which of these
are made from durable glass or near durable glass and add the clay we
need to keep it in suspension long enough for glazing our ware.
The problem which is the hardest to overcome - if the clay is not
vitrified enough to keep out water - the water will eventually
rehydrate the clay - and if the glaze is not crazed it will craze then.
The other problem is what happens to water in clay in the microwave
oven - the ware gets hot. It is important to permanently mark such
ware as not microwave safe.
RR
Quoting lili krakowski :
> Hi, Ron!
>
> In the Dark Ages of Quimper and other lovely leadglazed faience we
> did not consider lead solubility, or crazing and like that as
> dangers to the user.
>
> However now we know better--so my question is: CAN a c.04 and
> similar glaze ever be hard enough to resist modern detergents,
> dishwasher soaps, microwaving--not to mention the scratching by
> knives and forks.
>
>
> Lili Krakowski
> Be of good courage
>
Ron Roy on tue 2 mar 10
Hi James,
Not sure I am to answer this - but just in case - I have no idea.
I'd say it would be a good subject for an experiment but there are
more pressing questions to be answered.
I can say this though - depending of the stability of the glaze - it
may take a very long time. Even a stable glaze leaches.
You would certainly see the difference on the surface of the glaze -
from shiny to dull.
Sometimes - when I eat in a restaurant I will check the plates - often
they are less shiny on the upper surface and still shiny on the
bottom. That means the glaze is being leached by acidic food - which
only contacts the upper surface.
If the glaze is dulling bottom and top it is being attacked by soap -
on both sides. If the top is duller than the bottom then the glaze is
susceptible to both alkali and acid attack.
RR
Quoting James Freeman :
> And a related question, if you will: How many washings and eatings of
> acidic foods does it take until all of the free and leachable lead is
> leached and gone? In other words, can I eat off of an antique lead-glaze=
d
> dish safe in the knowledge that my forebears have unwittingly taken the
> bullet for me, having through use already eaten all of the lead there was=
to
> eat? It seems that if there is a finite quantity of lead in the glaze,
> there must also be a point where, through use and washing, there is no fr=
ee
> lead remaining.
>
> ...James
>
> James Freeman
>
> "All I say is by way of discourse, and nothing by way of advice. I shoul=
d
> not speak so boldly if it were my due to be believed."
> -Michel de Montaigne
>
> http://www.jamesfreemanstudio.com
> http://www.flickr.com/photos/jamesfreemanstudio/
> http://www.jamesfreemanstudio.com/clayart/
>
>
>
> On Tue, Mar 2, 2010 at 9:20 AM, lili krakowski
> wrote:
>
>>
>> In the Dark Ages of Quimper and other lovely leadglazed faience we did n=
ot
>> consider lead solubility, or crazing and like that as dangers to the use=
r.
>> However now we know better--so my question is: CAN a c.04 and similar gl=
aze
>> ever be hard enough to resist modern detergents, dishwasher soaps,
>> microwaving--not to mention the scratching by knives and forks.
>>
>
Ron Roy on tue 2 mar 10
And I'm sure there is a warning somewhere - in case some poor soul =3D20
decides it would make a good soup bowl - that would be the tradition =3D20
would it? No wait - we had to legislate that part because people were =3D20
getting sick eating pout of lead glazed pottery.
RR
Quoting Lee Love :
> On Tue, Mar 2, 2010 at 9:01 AM, James Freeman
> wrote:
>
> This is how we use a lead glazed Bowl, from the part of
> Pakistan/Afganistan the Tailban Hangout at:
>
> http://www.facebook.com/photo.php?pid=3D3D4111109&l=3D3D2fadb4c95a&id=3D3=
D550727=3D
056
>
>
>
> --
> --
> Lee, a Mashiko potter in Minneapolis
> http://mashikopots.blogspot.com/
>
> =3DE2=3D80=3D9CObserve the wonders as they occur around you. Don't claim =
them. F=3D
eel
> the artistry moving through and be silent.=3DE2=3D80=3D9D --Rumi
>
Lee Love on tue 2 mar 10
On Tue, Mar 2, 2010 at 6:36 PM, wrote:
> And I'm sure there is a warning somewhere -
Not actually. We bought two of these Pakistani bowls from Indigo
downtown in the '80s or early '90s. Elmer Fudd doesn't shop
there to much.
>that would be the tradition would it?
One True way? ;^) Who on Earth would propose "One True Way?" I never h=
=3D
ave.
Part of the tradition in both making and using functional ware,
ix paying attention to and respecting the materials.
We don't all wear wash & wear Or all polyester. We don't
all need to restrict ourselves to toilet bowl ceramics nor do we need
Dudley Doright padding all the corners in our living area because we
don't think folks are intelligent enough to treat things with respect.
I put more photos of the previous bowl and a second one. They
are inspirational, don't you think? I am making some lead free,
inspired by these:
http://www.facebook.com/album.php?aid=3D3D160813&id=3D3D550727056&l=3D3D29c=
039bc9=3D
b
---
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
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