Wanda Holmes at Alistia on sun 30 dec 01
Two of my favorite glazes contain lithium carbonate (1% in one case, 4% in
another). The recent discussions here raised a flag and sent me looking to
better understand the toxicity of lithium and the advisability of using it.
Nothing I've found makes it sound any worse than many of the other things we
use routinely - like cobalt or copper. Am I missing something? Is the
concern to me the potter while mixing and using the glaze? While firing the
glaze? Or is the concern to the user of a lithium glazed mug, cup, or bowl?
Thanks,
Wanda
John Hesselberth on sun 30 dec 01
on 12/30/01 1:12 AM, Wanda Holmes at Alistia at wanda.holmes@ALISTIA.COM
wrote:
> Two of my favorite glazes contain lithium carbonate (1% in one case, 4% in
> another). The recent discussions here raised a flag and sent me looking to
> better understand the toxicity of lithium and the advisability of using it.
> Nothing I've found makes it sound any worse than many of the other things we
> use routinely - like cobalt or copper. Am I missing something? Is the
> concern to me the potter while mixing and using the glaze? While firing the
> glaze? Or is the concern to the user of a lithium glazed mug, cup, or bowl?
>
> Thanks,
> Wanda
>
Hi Wanda,
Predicting whether or not handling lithium or lithium leaching is a problem
would be a very hazardous occupation. I can only offer some information;
you will have to make the determination yourself. First the hazard to you
is no worse than many of the other materials we use. If you are handling
silica in a way that will prevent you from getting silicosis (probably the
biggest hazard to studio potters) and otherwise using good safety practices,
you are not likely to be harmed by handling lithium carbonate.
Second, while many Clayart members can help you formulate a stable glaze,
none of us can predict exactly how much lithium or anything else will leach
out in use. Only having your glazes tested will tell that. If the glaze is
a really bad glaze overall, then lithium in measurable quantities would
leach out even if it were only at the 1% level. If you will post the recipe,
I or any of several other people can give you an opinion on whether your
glaze is likely to be stable or not--but only testing can quantify that.
Now to the question of "so what if it does leach?" Again I can only offer a
little information. Lithium acetate, lithium citrate and lithium sulfate
(the forms most likely to be formed via leaching by acidic foods) are all
listed in the Merck Index as antimanics and/or antidepressants, i.e. they
can be used therapeutically to treat mental disorders. It is my
understanding that they are sometimes used at levels close to a toxic level.
Can a little added lithium leached into coffee upset the balance of someone
who is already taking lithium? Who knows? I certainly would not pretend
to. Neither would I particularly want to run the experiment. For people not
taking lithium for medicinal purposes, I think the chances of lithium
leaching causing any kind of problem would be very small.
All that said, I would personally not use lithium without being sure it was
in a very stable glaze and way toward the stable end of the spectrum. But
that is my philosophy about glaze ingredients in general. I do that not
only to eliminate any safety concerns, present or future, that might exist,
but also to make sure my glazes will be durable in use. Unfortunately a lot
of glazes floating around in potter-land are not very durable. I just wish
there were a way to stamp a big red UNSTABLE on their foreheads--maybe
someday there will be.
If you are planning to attend NCECA you'll probably find me in the Clayart
(Alice's) room at some point with a bowl of lemon slices and some examples
of stable and unstable glazes. It is pretty amazing how bad some "glazes"
are--I use the quotation marks because some of them don't even deserve to be
called a glaze.
Regards,
John
web sites: http://www.masteringglazes.com and http://www.frogpondpottery.com
EMail: john@frogpondpottery.com
"It is, perhaps, still necessary to say that the very best glazes cannot
conceal badly shaped pots..." David Green, Pottery Glazes
Wanda Holmes on sun 30 dec 01
Regarding my question about the toxicity of lithium carbonate, several of
you have asked me to post the recipes I am using to inform your response.
On of them is Pete Pinnell's Weathered Green Bronze. I use that particular
recipe and I also use the base with other colorants rather than copper -
cobalt, chrome, rutile. The amounts of cobalt carbonate I use range from .1
to 4%, rutile from 6-12%, chrome less than 1%.
The other recipe I use that contains lithium carbonate is from Bailey's Cone
6 book. It is T12. The recipe and formula are:
Potash feldspar 44.0
China clay 6.0
Bentonite 2.0
Lithium carbonate 4.0
Whiting 14.0
Zinc oxide 5.0
Flint 24.0
Na2O 0.07 Al2O3 0.30 SiO2 2.94
K2O 0.15 P2O5 0.00
MgO 0.00 TiO2 0.00
CaO 0.43 Fe2O3 0.00
Li2O 0.16
ZnO 0.19
Alumina:Silica ratio is 1.00:9.65
Neutral:Acid ratio is 1.00:9.67
Alk:Neut:Acid ratio is 1.00:0.30:2.94
I use the same colorants in generally the same amounts in it: Copper carb
1-5%, cobalt carb .5-4%, rutile 6-12%.
Thank you to all of you who have responded and for your offer to consider
the question further once you had more information. I am humbled by how
wonderful all of you are.
Wanda
Ababi on mon 31 dec 01
I see we use different software.
About Weathered Bronze books were written!
About T-1:
This is definitely a decorative glaze.
This morning I read in Tony Hansen's book That I should avoid copper
and zinc. So, Mike Bailey, did not read it and combined zinc+ lithium +
copper. real beauty. I think if I will succeed and remove the lithium
will be like removing the yellow cheese from the pizza.
Instead I shall give you another decorative base I use. I posted it
before, about every three month.
It has strontium that works good with copper and zinc that we better
not use with copper.
I will give it in two ways. The first, as it is. The second based on
the fact that recently i discovered the secret analysis of the
feldspars i have, would be adjusted according to it.
In my first glaze page you can see it. It is based on a recipe I got
from a well known teacher in Israel, Yehuda Koren, his base by the way,
had barium and lithium too!
Koren Strontium
===============
QUARTZ.............. 27.15 27.15%
FELDSPAR soda....... 36.55 36.55%
WHITING............. 13.58 13.58%
ENGLISH KAOLIN(cc 31) 5.22 5.22%
ZINC OXIDE.......... 10.44 10.44%
STRONTIUM CARBONATE. 7.05 7.05%
You can try it this way too.
Koren strontium2
================
QUARTZ.............. 36.3 36.42%
WHITING............. 13.6 13.64%
KAOLIN cc31......... 4.7 4.74%
ZINC OXIDE.......... 10.4 10.49%
STRONTIUM CARBONATE. 7.1 7.08%
NEPHELINE SYENITE... 27.5 27.63%
========
99.6
CaO 0.37* 8.49%
MgO 0.00* 0.01%
K2O 0.04* 1.61%
Na2O 0.13* 3.22%
ZnO 0.34* 11.48%
SrO 0.13* 5.44%
TiO2 0.00 0.01%
Al2O3 0.21 8.99%
SiO2 2.44 60.68%
Fe2O3 0.00 0.06%
Text1 8.97
Si:Al 11.45
SiB:Al 11.45
Expan 7.52
Is it foodsafe? very low alumina, I do not think so, yet as decorative
glaze safer can give you brilliant surface. Test it on several
claybodys.
In my next ^6 I will test some daughter glazes of this one.
I must go now to sniff glazes
Bye bye
Ababi Sharon
Kibbutz Shoval- Israel
Glaze addict
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
http://www.israelceramics.org/
---------- Original Message ----------
>Regarding my question about the toxicity of lithium carbonate, several
>of
>you have asked me to post the recipes I am using to inform your
>response.
>On of them is Pete Pinnell's Weathered Green Bronze. I use that
>particular
>recipe and I also use the base with other colorants rather than copper
-
>cobalt, chrome, rutile. The amounts of cobalt carbonate I use range
>from .1
>to 4%, rutile from 6-12%, chrome less than 1%.
>The other recipe I use that contains lithium carbonate is from
Bailey's
>Cone
>6 book. It is T12. The recipe and formula are:
>Potash feldspar 44.0
>China clay 6.0
>Bentonite 2.0
>Lithium carbonate 4.0
>Whiting 14.0
>Zinc oxide 5.0
>Flint 24.0
> Na2O 0.07 Al2O3 0.30 SiO2 2.94
> K2O 0.15 P2O5 0.00
> MgO 0.00 TiO2 0.00
> CaO 0.43 Fe2O3 0.00
> Li2O 0.16
> ZnO 0.19
>Alumina:Silica ratio is 1.00:9.65
>Neutral:Acid ratio is 1.00:9.67
>Alk:Neut:Acid ratio is 1.00:0.30:2.94
>I use the same colorants in generally the same amounts in it: Copper
>carb
>1-5%, cobalt carb .5-4%, rutile 6-12%.
>Thank you to all of you who have responded and for your offer to
>consider
>the question further once you had more information. I am humbled by
how
>wonderful all of you are.
>Wanda
>_______________________________________________________________________
_
>______
>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.
The Mask (& Puppet) Studio on mon 31 dec 01
Lithium therapy was discovered by an Australian doctor in the
1960s and is still used standardly in the treatment of (usually)
bipolar manic depression. However, its toxicity is a major side
effect. Those on Li2CO3 treatment need to be monitored frequently
initially and then occasionally to ensure two things:
(1) That the therapeutic level has been reached. Lithium won't work
unless it attains a threshold in the blood stream
(2) That the lithium level isn't toxic. This can have consequences
especially on liver function (and does with long termuse of lithioum
in therapy).
The problem is that there is not much room between therapeutic
and toxic levels of lithium. Any hint of toxicity is simply treated by
withdrawing the drug.
As lithium is a naturally occurring compound we will also find it in
many mineral waters ( check the labels as it should be listed). This
doesn't make it benign but I need to suggest that unless it is in
solution the salt is unlikley to be absorbed by the body.
For those who don't suffer from the complex of symptoms
assocated with Manic Depression -- lithium will have no impact on
behaviour.
Dave Riley
(who spent 20 years working in psychiatric hospitals)
John Hesselberth on mon 31 dec 01
Hi Wanda,=20
Pete's Weathered Bronze Green has been discussed many times on this list an=
d
has been found to be quite stable to leaching IF it is fired to a full larg=
e
cone 6 tip touching (that's different from a small cone 6 shutting off a
Kiln Sitter=AE). It has only been leach tested for copper (see my web site
for the results), but copper is the most difficult thing to keep in a glaze=
.
I would note that this is a glaze that was developed for cone 10 and found
to be OK at cone 6, but that is why it really has to be fired to a full con=
e
6--not less--to be stable. I personally don't worry about lithium leaching
from this glaze, but I have not tested specifically for it.
The second glaze is reasonably well balanced with enough alumina and silica
to be fairly stable to leaching IF you don't overload it with colorants. 5%
copper carbonate is a high loading--so is 4% cobalt carbonate. If you are
using those colorant levels with this glaze you may get significant
leaching. However, note that this glaze also contains zinc and, if your
remember the discussion of a couple weeks ago, it seems that the combinatio=
n
of zinc and lithium may be what gives crazing and shivering on the same pot=
.
I would test this glaze extremely carefully before I used it on any
functional work--in fact I wouldn't use it myself until the
crazing/shivering/lithium/zinc phenomena that some have observed is better
understood.
Please remember that my comments are only opinions. You must test your
glazes using your ingredients, your mixing, your application and your firin=
g
conditions to really know what you have.
I hope this helps.
Regards,
John
on 12/30/01 11:00 PM, Wanda Holmes at wmedcalf@TEXAS.NET wrote:
> Regarding my question about the toxicity of lithium carbonate, several of
> you have asked me to post the recipes I am using to inform your response.
> On of them is Pete Pinnell's Weathered Green Bronze. I use that particul=
ar
> recipe and I also use the base with other colorants rather than copper -
> cobalt, chrome, rutile. The amounts of cobalt carbonate I use range from=
.1
> to 4%, rutile from 6-12%, chrome less than 1%.
>=20
> The other recipe I use that contains lithium carbonate is from Bailey's C=
one
> 6 book. It is T12. The recipe and formula are:
>=20
> Potash feldspar 44.0
> China clay 6.0
> Bentonite 2.0
> Lithium carbonate 4.0
> Whiting 14.0
> Zinc oxide 5.0
> Flint 24.0
>=20
> Na2O 0.07 Al2O3 0.30 SiO2 2.94
> K2O 0.15 P2O5 0.00
> MgO 0.00 TiO2 0.00
> CaO 0.43 Fe2O3 0.00
> Li2O 0.16
> ZnO 0.19
>=20
> Alumina:Silica ratio is 1.00:9.65
> Neutral:Acid ratio is 1.00:9.67
> Alk:Neut:Acid ratio is 1.00:0.30:2.94
>=20
> I use the same colorants in generally the same amounts in it: Copper carb
> 1-5%, cobalt carb .5-4%, rutile 6-12%.
>=20
> Thank you to all of you who have responded and for your offer to consider
> the question further once you had more information. I am humbled by how
> wonderful all of you are.
>=20
> Wanda
>=20
Web sites: http://www.masteringglazes.com and http://www.frogpondpottery.co=
m
Email: john@frogpondpottery.com
"Art is not a handicraft, it is the transmission of feeling the artist has
experienced." Leo Tolstoy, 1898
Ababi on mon 31 dec 01
Hello Wanda!
You read , and should read again John's words.
Let me be wider.
We have some good poisons. Even if we do not know what they do.
We must be very carful.
We can of course read and get wider information. You can read Monona
Rossol's book.
If you like these glazes, try to imitate them without lithium.
I succeeded to do it so far with too glazes.
The 1% lithium is important when you need mottling effect.
The lithium contributes to lower expansion as well as turquoise from
copper which otherwise with sodium your glaze might be crackled.
You can send me the recipes if these are ^6 glazes ox. I am not a busy
person I can try to adjust them. Not for sure the ultimate food safe,
just trying to make them with after fire food materials.
Silica-in-the-glaze is such, unless you eat the glaze!
Ababi Sharon
Kibbutz Shoval- Israel
Glaze addict
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
http://www.israelceramics.org/
---------- Original Message ----------
>Two of my favorite glazes contain lithium carbonate (1% in one case,
4%
>in
>another). The recent discussions here raised a flag and sent me
>looking to
>better understand the toxicity of lithium and the advisability of
using
>it.
>Nothing I've found makes it sound any worse than many of the other
>things we
>use routinely - like cobalt or copper. Am I missing something? Is the
>concern to me the potter while mixing and using the glaze? While
firing
>the
>glaze? Or is the concern to the user of a lithium glazed mug, cup, or
>bowl?
>Thanks,
>Wanda
>_______________________________________________________________________
_
>______
>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.
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