Jon Singer on sat 30 oct 99
Garry Wakely asks about possible
toxicity from lithium, and says,
"I have heard that lithium based glazes are not suitable for food
wares, but can find no articles to back this up."
There is a reason for that. I doubt that you'll find any
such backup, because I don't think there is any.
"Is it safe? Is it unsafe? My assumptions were that lithium acted
like barium in that it would leach back out of the fired glaze, but
I now am no longer sure. Can someone fill me in, please?"
First of all, lithium should probably act more like sodium
and potassium (to which it is closely related) than like barium,
though it is a smaller ion than either sodium or potassium.
Second, if you check _Ceramic_Glazes_, 3rd edition, by
Parmelee and Harman, what you will find is that addition
of lithium to a glaze for porcelain INCREASES both the
hardness of the glaze (that is, its resistance to mechanical
abrasion) and its resistance to chemical attack. In other words:
no, lithium does not seem to leach out, and yes, it seems to
be quite safe for food.
In fact, if you read the letter column of the current Ceramics
Monthly (the one with the excellent article on copper red
glazes by David Hendley) you will find a letter titled "The
Power of Spodumene" from a guy who is in the mineral
industry, pointing out (among other things) that lithium
is already widely used in the ceramics industry, mostly in
glazes but also to some extent in ovenproof & flameproof
bodies.
In my own career as a student, I have been finding that
lithium helps me control the expansion of my glazes. If
you want to see examples, there's a high-lithium clear
glaze on the pieces in the photos at
http://www.bazilians.org/show.whiteware.html,
and even my rutile blue
(http://www.bazilians.org/show.rutileblue.html)
has a rather large amount of lithium in it. The clear is
clear, and the blue is blue. (That is, lithium doesn't seem
to add any particular color of its own, and it also doesn't
interfere with the formation of other colors, though it
may change the values of certain colors slightly.)
Best wishes --
jon
Ron Roy on sun 31 oct 99
It is true that lithium is an alkaline flux - like sodium and potassium and
also promotes leaching if out of balance with other fluxes. Some glazes
will leach a lot and some will leach less - it depends on many other
factors. If you don't know about this and you don't have your glazes tested
for lithium release - then don't do it is my best advice.
Lithium is toxic if you go over the limit - many control their manic
depression with lithium and some are near or over the toxic limit. I see no
reason to use it except under very special circumstances.
There is some room here for some experimentation. Lithium Carb is a lot
different from Spodumene or Petalite. I'll bet it's a lot safer to source
lithium from Spod or Petalite than from the carbonate.
The carbonate is slightly soluble and leads to problems in the bucket - and
because some is migrating to the glaze surface during evaporation is
presents another possible problem.
There is still another problem with at least the carbonate - I have seen
glazes with lithium carbonate craze and shiver - on the same pot.
This is not a material to take lightly.
RR
>----------------------------Original message----------------------------
>Second, if you check _Ceramic_Glazes_, 3rd edition, by
>Parmelee and Harman, what you will find is that addition
>of lithium to a glaze for porcelain INCREASES both the
>hardness of the glaze (that is, its resistance to mechanical
>abrasion) and its resistance to chemical attack. In other words:
>no, lithium does not seem to leach out, and yes, it seems to
>be quite safe for food.
>
>In fact, if you read the letter column of the current Ceramics
>Monthly (the one with the excellent article on copper red
>glazes by David Hendley) you will find a letter titled "The
>Power of Spodumene" from a guy who is in the mineral
>industry, pointing out (among other things) that lithium
>is already widely used in the ceramics industry, mostly in
>glazes but also to some extent in ovenproof & flameproof
>bodies.
Ron Roy
93 Pegasus Trail,
Scarborough, Ontario
Canada. M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Louis H.. Katz on sun 31 oct 99
There is a bit of bad logic in the assertion that if litium is sometimes
added to increase durability then it must not leach from glazes.
Louis
>
> Second, if you check _Ceramic_Glazes_, 3rd edition, by
> Parmelee and Harman, what you will find is that addition
> of lithium to a glaze for porcelain INCREASES both the
> hardness of the glaze (that is, its resistance to mechanical
> abrasion) and its resistance to chemical attack. In other words:
> no, lithium does not seem to leach out, and yes, it seems to
> be quite safe for food.
Earl Brunner on mon 1 nov 99
I understand what you are saying about the differences between Spodumene and
lithium carb.... but given the newer (my experiences with spodumene date to the
70's and it was much different) spodumene, just how different is the newr
spodumene than lithium carb? The stuff I have in the lab looks and feels about
the same. Is it possible that someone is selling the same product under both
names?
Ron Roy wrote:
> ----------------------------Original message----------------------------
> It is true that lithium is an alkaline flux - like sodium and potassium and
> also promotes leaching if out of balance with other fluxes. Some glazes
> will leach a lot and some will leach less - it depends on many other
> factors. If you don't know about this and you don't have your glazes tested
> for lithium release - then don't do it is my best advice.
>
> Lithium is toxic if you go over the limit - many control their manic
> depression with lithium and some are near or over the toxic limit. I see no
> reason to use it except under very special circumstances.
>
> There is some room here for some experimentation. Lithium Carb is a lot
> different from Spodumene or Petalite. I'll bet it's a lot safer to source
> lithium from Spod or Petalite than from the carbonate.
>
> The carbonate is slightly soluble and leads to problems in the bucket - and
> because some is migrating to the glaze surface during evaporation is
> presents another possible problem.
>
> There is still another problem with at least the carbonate - I have seen
> glazes with lithium carbonate craze and shiver - on the same pot.
>
> This is not a material to take lightly.
>
> RR
>
> >----------------------------Original message----------------------------
> >Second, if you check _Ceramic_Glazes_, 3rd edition, by
> >Parmelee and Harman, what you will find is that addition
> >of lithium to a glaze for porcelain INCREASES both the
> >hardness of the glaze (that is, its resistance to mechanical
> >abrasion) and its resistance to chemical attack. In other words:
> >no, lithium does not seem to leach out, and yes, it seems to
> >be quite safe for food.
> >
> >In fact, if you read the letter column of the current Ceramics
> >Monthly (the one with the excellent article on copper red
> >glazes by David Hendley) you will find a letter titled "The
> >Power of Spodumene" from a guy who is in the mineral
> >industry, pointing out (among other things) that lithium
> >is already widely used in the ceramics industry, mostly in
> >glazes but also to some extent in ovenproof & flameproof
> >bodies.
> Ron Roy
>
> 93 Pegasus Trail,
> Scarborough, Ontario
> Canada. M1G 3N8
>
> Tel: 416-439-2621
> Fax: 416-438-7849
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
Tasha Olive on mon 1 nov 99
Ron I think I shall try the Pinnell weathered bronze that has been being
given without the 1% of lithium, instead just putting the 1% into the
strontium.......will let all know of the outcome. Tasha who likes to use as
little as possible that is controversial in its safety.. too much we HAVE to
use as it is.
-----Original Message-----
From: Ron Roy
To: CLAYART@LSV.UKY.EDU
Date: Sunday, October 31, 1999 9:27 PM
Subject: Re: Lithium glazes --
----------------------------Original message----------------------------
It is true that lithium is an alkaline flux - like sodium and potassium and
also promotes leaching if out of balance with other fluxes. Some glazes
will leach a lot and some will leach less - it depends on many other
factors. If you don't know about this and you don't have your glazes tested
for lithium release - then don't do it is my best advice.
Lithium is toxic if you go over the limit - many control their manic
depression with lithium and some are near or over the toxic limit. I see no
reason to use it except under very special circumstances.
There is some room here for some experimentation. Lithium Carb is a lot
different from Spodumene or Petalite. I'll bet it's a lot safer to source
lithium from Spod or Petalite than from the carbonate.
The carbonate is slightly soluble and leads to problems in the bucket - and
because some is migrating to the glaze surface during evaporation is
presents another possible problem.
There is still another problem with at least the carbonate - I have seen
glazes with lithium carbonate craze and shiver - on the same pot.
This is not a material to take lightly.
RR
>----------------------------Original message----------------------------
>Second, if you check _Ceramic_Glazes_, 3rd edition, by
>Parmelee and Harman, what you will find is that addition
>of lithium to a glaze for porcelain INCREASES both the
>hardness of the glaze (that is, its resistance to mechanical
>abrasion) and its resistance to chemical attack. In other words:
>no, lithium does not seem to leach out, and yes, it seems to
>be quite safe for food.
>
>In fact, if you read the letter column of the current Ceramics
>Monthly (the one with the excellent article on copper red
>glazes by David Hendley) you will find a letter titled "The
>Power of Spodumene" from a guy who is in the mineral
>industry, pointing out (among other things) that lithium
>is already widely used in the ceramics industry, mostly in
>glazes but also to some extent in ovenproof & flameproof
>bodies.
Ron Roy
93 Pegasus Trail,
Scarborough, Ontario
Canada. M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
susanford on mon 1 nov 99
Coming in on the tail end of this converstion... I am in
the process of setting up a glaze lab and have some of my
base materials. I do not wish to use lithium, but I have
many glaze recipies, in books, that use it. How would you
subsitute spodumene for lithium carbonate? I figure it
can't be a straight substitution, though I guess I could do
a test batch and see...
Susan
> ----------------------------Original message----------------------------
> I understand what you are saying about the differences between Spodumene and
> lithium carb.... but given the newer (my experiences with spodumene date to th
> 70's and it was much different) spodumene, just how different is the newr
> spodumene than lithium carb? The stuff I have in the lab looks and feels abou
> the same. Is it possible that someone is selling the same product under both
> names?
>
> Ron Roy wrote:
>
> > ----------------------------Original message----------------------------
> > It is true that lithium is an alkaline flux - like sodium and potassium and
> > also promotes leaching if out of balance with other fluxes. Some glazes
> > will leach a lot and some will leach less - it depends on many other
> > factors. If you don't know about this and you don't have your glazes tested
> > for lithium release - then don't do it is my best advice.
> >
> > Lithium is toxic if you go over the limit - many control their manic
> > depression with lithium and some are near or over the toxic limit. I see no
> > reason to use it except under very special circumstances.
> >
> > There is some room here for some experimentation. Lithium Carb is a lot
> > different from Spodumene or Petalite. I'll bet it's a lot safer to source
> > lithium from Spod or Petalite than from the carbonate.
> >
> > The carbonate is slightly soluble and leads to problems in the bucket - and
> > because some is migrating to the glaze surface during evaporation is
> > presents another possible problem.
> >
> > There is still another problem with at least the carbonate - I have seen
> > glazes with lithium carbonate craze and shiver - on the same pot.
> >
> > This is not a material to take lightly.
> >
> > RR
> >
> > >----------------------------Original message----------------------------
> > >Second, if you check _Ceramic_Glazes_, 3rd edition, by
> > >Parmelee and Harman, what you will find is that addition
> > >of lithium to a glaze for porcelain INCREASES both the
> > >hardness of the glaze (that is, its resistance to mechanical
> > >abrasion) and its resistance to chemical attack. In other words:
> > >no, lithium does not seem to leach out, and yes, it seems to
> > >be quite safe for food.
> > >
> > >In fact, if you read the letter column of the current Ceramics
> > >Monthly (the one with the excellent article on copper red
> > >glazes by David Hendley) you will find a letter titled "The
> > >Power of Spodumene" from a guy who is in the mineral
> > >industry, pointing out (among other things) that lithium
> > >is already widely used in the ceramics industry, mostly in
> > >glazes but also to some extent in ovenproof & flameproof
> > >bodies.
> > Ron Roy
> >
> > 93 Pegasus Trail,
> > Scarborough, Ontario
> > Canada. M1G 3N8
> >
> > Tel: 416-439-2621
> > Fax: 416-438-7849
>
> --
> Earl Brunner
> http://coyote.accessnv.com/bruec
> mailto:bruec@anv.net
>
>
---
Susan K. Ford
Norman, Oklahoma
http://www.clueless.norman.ok.us/sf/rerhome.htm
mary simmons on tue 2 nov 99
Earl-
Spodumene (LiAlSi2O6) is a lithium-rich pyroxene, which is a silicate, so
there'll be some Si-O and Al-O tetrahedra present. In all silicates silica
and aluminum bond to 3 oxygen atoms in tetrahedrons, which are simply
pyramids where four large oxygen atoms surround a much smaller silica or
aluminum atom. Sodium can substitute for some of the lithium in spodumene.
Lithium carbonate has no silica or aluminum, and firing it breaks down to
LiO + CO2, the CO2 of course goes away as a gas in the kiln atmosphere. In
the natural world of rocks and minerals, there is no such animal :) as
lithium carbonate (that I know of)--so this compound must be synthesized.
Lithium carbonate may be a weathering product of some other lithium-rich
mineral, such as spodumene (which weathers to clay) once the lithium is
liberated, and if it finds its way into water, there are ALWAYS carbonate
ions, with an unbalanced charge, swimming around looking for something to
hook up with. It is more likely that the LiCO3 you are using is
synthesized, and so perhaps relatively pure.
So, no matter how new or old your spodumene is, it is very different from
lithium carb.
your resident geo-geek
Mary
Mary Simmons
Dept of Earth and Planetary Sciences
University of New Mexico
(505)277-9259
piedra@unm.edu
Ron Roy on thu 4 nov 99
Hi Earl. I know someone else has answered this but - I should add -
best to do this conversion from the carbonate to the lithium
alumo-silicates with calculation.
Many glazes have the carbonate in them because most potters simply
needed more melt and because they did not - for whatever reasons -
understand how to do it using other fluxes - or - to put it another
way - it is a simple fix but with some adverse effects. Many times
the Lithium is not needed at all.
It is common for potters to use simple materials because they do not
understand enough to make revisions any other way - this is changing
now because calculation software does the grunt work so easily - and
our glazes are getting better because of the understanding we must
have to use the software.
Lithium is a complex flux for us - in smaller amounts it can lower
the expansion of a glaze if it is subbed for KNaO. But if it added in
greater amounts this quality reverses itself.
RR
>----------------------------Original message----------------------------
>I understand what you are saying about the differences between Spodumene and
>lithium carb.... but given the newer (my experiences with spodumene
>date to the
>70's and it was much different) spodumene, just how different is the newr
>spodumene than lithium carb? The stuff I have in the lab looks and
>feels about
>the same. Is it possible that someone is selling the same product under both
>names?
>
>Ron Roy wrote:
>
> > ----------------------------Original message----------------------------
> > It is true that lithium is an alkaline flux - like sodium and potassium and
> > also promotes leaching if out of balance with other fluxes. Some glazes
> > will leach a lot and some will leach less - it depends on many other
> > factors. If you don't know about this and you don't have your glazes tested
> > for lithium release - then don't do it is my best advice.
> >
> > Lithium is toxic if you go over the limit - many control their manic
> > depression with lithium and some are near or over the toxic limit. I see no
> > reason to use it except under very special circumstances.
> >
> > There is some room here for some experimentation. Lithium Carb is a lot
> > different from Spodumene or Petalite. I'll bet it's a lot safer to source
> > lithium from Spod or Petalite than from the carbonate.
> >
> > The carbonate is slightly soluble and leads to problems in the bucket - and
> > because some is migrating to the glaze surface during evaporation is
> > presents another possible problem.
> >
> > There is still another problem with at least the carbonate - I have seen
> > glazes with lithium carbonate craze and shiver - on the same pot.
> >
> > This is not a material to take lightly.
> >
> > RR
> >
> > >----------------------------Original message----------------------------
> > >Second, if you check _Ceramic_Glazes_, 3rd edition, by
> > >Parmelee and Harman, what you will find is that addition
> > >of lithium to a glaze for porcelain INCREASES both the
> > >hardness of the glaze (that is, its resistance to mechanical
> > >abrasion) and its resistance to chemical attack. In other words:
> > >no, lithium does not seem to leach out, and yes, it seems to
> > >be quite safe for food.
> > >
> > >In fact, if you read the letter column of the current Ceramics
> > >Monthly (the one with the excellent article on copper red
> > >glazes by David Hendley) you will find a letter titled "The
> > >Power of Spodumene" from a guy who is in the mineral
> > >industry, pointing out (among other things) that lithium
> > >is already widely used in the ceramics industry, mostly in
> > >glazes but also to some extent in ovenproof & flameproof
> > >bodies.
> > Ron Roy
> >
> > 93 Pegasus Trail,
> > Scarborough, Ontario
> > Canada. M1G 3N8
> >
> > Tel: 416-439-2621
> > Fax: 416-438-7849
>
>--
>Earl Brunner
>http://coyote.accessnv.com/bruec
>mailto:bruec@anv.net
Ron Roy
93 Pegasus Trail,
Scarborough, Ontario
Canada. M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Ron Roy on thu 4 nov 99
Hi Mary,
I just love the way you talk - and what you talk about - RR
>
>Spodumene (LiAlSi2O6) is a lithium-rich pyroxene, which is a silicate, so
>there'll be some Si-O and Al-O tetrahedra present. In all silicates silica
>and aluminum bond to 3 oxygen atoms in tetrahedrons, which are simply
>pyramids where four large oxygen atoms surround a much smaller silica or
>aluminum atom. Sodium can substitute for some of the lithium in spodumene.
>
>Lithium carbonate has no silica or aluminum, and firing it breaks down to
>LiO + CO2, the CO2 of course goes away as a gas in the kiln atmosphere. In
>the natural world of rocks and minerals, there is no such animal :) as
>lithium carbonate (that I know of)--so this compound must be synthesized.
>Lithium carbonate may be a weathering product of some other lithium-rich
>mineral, such as spodumene (which weathers to clay) once the lithium is
>liberated, and if it finds its way into water, there are ALWAYS carbonate
>ions, with an unbalanced charge, swimming around looking for something to
>hook up with. It is more likely that the LiCO3 you are using is
>synthesized, and so perhaps relatively pure.
>
>So, no matter how new or old your spodumene is, it is very different from
>lithium carb.
>
>your resident geo-geek
>Mary
>
>Mary Simmons
>Dept of Earth and Planetary Sciences
>University of New Mexico
>(505)277-9259
>piedra@unm.edu
Ron Roy
93 Pegasus Trail,
Scarborough, Ontario
Canada. M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
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