Ron Roy on mon 10 mar 97
>>Just a word of caution here. The cones Lawrence is talking about are 10
>>and 11. I would not think the same improvement would be found between, for
>>instance, cone 6 and 7.
>>
>>Ron Roy
>Ron,
>
>Thanks for that important clarification. Could you expand on your
>observation relating to the different results which might be expected at
>lower temperatures? I note in Janet's research report that she suggests
>further research should be undertaken at the lower temperatures.
>
>Lawrence Ewing
>Dunedin
>New Zealand.
Dear Laurence,
I have just done a comparison between the 2 limit formulas I use and the
first 16 glazes in Janet's examples. My first observation is that none of
the glazes fall within the limits for cone 10. If I ignore the "above the
limits" amount of Alumina" then some do. If you compare these recipes to
limit formulas you will see - as the Barium increases and the Silica
decreases the Barium release increases. Also as the amount of Silica
approaches the lower limit for SiO2 amounts released increase.
It got so that I could forecast the increase in Barium release by comparing
the molecular formula of each glaze to the limits I used based on Barium
and Silica parts.
The Alumina was not much of a factor - my understanding is that Alumina has
more to do with alkaline attack so that made sense.
There is little or no Calcium present in these test glazes - I would think
it would have an influence on release. My understanding is that calcium
would have made these glazes more durable. I am not quibbling here with
Janet's approach by the way - her experiments are enlightening and
educational in a very real way.
To answer the question that Lawrence poses - Firing at higher temperatures
allows more silica and alumina in glazes - that makes possible "better"
(more durable) glazes. At lower temperatures the "glass" cannot have as
much because you need more flux to melt at a lower temperature. I don't
mean to say it is impossible to make durable glazes at lower temperatures -
I mean it is more difficult, takes more skill (or luck) and there is more
room for failure.
There was Barium release from all 30 glazes at both temperatures. Some were
very little but at cone 10 twelve released more than the current limit of
one part per million - some way more - like over 200 parts.
Yes I think testing at lower temperatures will be even more revealing and I
support any kind of real testing instead of opinion. To that end I
encourage everyone to support Janet for doing this and I hope that support
results in further testing. Those of us who believe in getting this kind of
work done need all the support and encouragement we can get. We give up
other parts of our lives so that we may all benefit - at a cost. Many pots
don't get made, families are ignored, and we spend our energies trying to
make sure we don't publish misleading results - all the while the bank
account shrinks.
If you think this kind of research is valuable then why not send for the
booklets with the complete results of this testing - which includes the
effect of copper on Barium Release which is not included in the article.
Janet DeBoos
The Ceramics Workshop
Australian National University School of Art
PO Box 804
Canberra
ACT 2601
Australia
Cost is: A$10 payable to the Ceramics Workshop
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Ron Roy on tue 11 mar 97
If you think this kind of research is valuable then why not send for the
booklet with the complete results of this testing - which includes the
effect of copper on Barium Release which is not included in the article.
Janet DeBoos
The Ceramics Workshop
Australian National University School of Art
PO Box 804
Canberra
ACT 2601
Australia
Cost is: A$10 payable to the Ceramics Workshop
An addendum to the post I sent last night. I tried to buy an international
money order to order the booklet but it was too expensive - use your credit
card.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
PJLewing@aol.com on tue 11 mar 97
I've been playing around with a barium frit, Ferro 3289, and getting some
very interesting colors. Seems you can get a lot more barium into a ^5 glaze
if it's in the form of this frit than if it's the carbonate, and get a much
more fluid melt with the same amount of barium.
I have two questions about using the frit, though. First, does fritting the
barium decrease the solubility, as with lead? And second, this frit has
equal amounts of boron and barium. Does the boron increase the solubility of
the barium?
I should also say that I only do tiles, and would not put one of these glazes
on functional ware. One variation with copper gives a wonderful intense
green I have not seen in any other base. It's probably deadly, but damn, is
it pretty!
Paul Lewing
In Seattle, where the cold rain has turned to cool rain.
Ron Roy on wed 12 mar 97
>I've been playing around with a barium frit, Ferro 3289, and getting some
>very interesting colors. Seems you can get a lot more barium into a ^5 glaze
>if it's in the form of this frit than if it's the carbonate, and get a much
>more fluid melt with the same amount of barium.
>I have two questions about using the frit, though. First, does fritting the
>barium decrease the solubility, as with lead? And second, this frit has
>equal amounts of boron and barium. Does the boron increase the solubility of
>the barium?
>I should also say that I only do tiles, and would not put one of these glazes
>on functional ware. One variation with copper gives a wonderful intense
>green I have not seen in any other base. It's probably deadly, but damn, is
>it pretty!
Hi Paul,
First of all the article by Janet goes into the effect of Barium on mamals
- just how "deadly" the Barium which leaches out of a glaze is. This seems
to be very difficult to assess. My wild guess is that it will affect some
more than others depending on susceptability, dose, body weight and back
ground levels. The real issue, as I see it, will be the hysterical reaction
of the general public when they find out about Barium in the media and that
some glazes have it in them. It happened many times with lead and the
result was deceased sales in proportion to the proximity to the story. I
just feel that producing potters have a hard enough row to hoe without
having to overcome negative publicity.
Does boron increase the solubility of the Barium. Not covered in Janet's
experiments. I would guess yes but I don't know. Sodium and Copper will. In
order to guess better I need the firing temp and recipe.
Does using a frit decrease lead or barium release - if that is the question
the answer is no - not for lead, nor for Barium or anything else. After
firing the frit has changed. Think of the glaze as a frit. It can be a good
glass or a poor glass depending on materials added and firing temperature.
I would be very interested to find where the information is on just how
"safe" frits are - especially when tested with food or respirated.
Anyone using frits, stains, under glaze, overglaze, with hazardous
materials in them, should should take precauctions. Don't breath em, don't
eat em and, in some cases, stay out of the kiln room when firing em.
As Monona has stated - long term exposure is what we have to avoid - the
occasional exposure, I don't think, is much of a problem. I must add as
well that I have had some near misses with carbon monoxide over the last 35
years - when the wind is blowing the wrong way I am thankful for my CO
detector.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Roger Gallardo on sat 15 mar 97
Can someone please tell us what barium compound is being released
with your testing. This is important to determine toxicity of the
compound. An example: barium carbonate is toxic; barium sulphate is
non-toxic. This is what you drink when you have your stomach
x-rayed.
Almost all forms of barium compounds are non-toxic. Another example
is a frit containing barium. Some people are saying that because a frit
contains barium, it is toxic, just because it is listed as barium.
This is false. The barium in a frit is a barium compound and is
non-toxic. Barium cannot exist as an element. It must be in
combination with another material.
Roger Gallardo
Technical Advisor
Laguna Clay Co. CA
Paul Monaghan on sun 16 mar 97
Roger Gallardo wrote:
>
> ----------------------------Original message----------------------------
> Can someone please tell us what barium compound is being released
> with your testing. This is important to determine toxicity of the
> compound. An example: barium carbonate is toxic; barium sulphate is
> non-toxic. This is what you drink when you have your stomach
> x-rayed.
> Almost all forms of barium compounds are non-toxic. Another example
> is a frit containing barium. Some people are saying that because a frit
> contains barium, it is toxic, just because it is listed as barium.
> This is false. The barium in a frit is a barium compound and is
> non-toxic. Barium cannot exist as an element. It must be in
> combination with another material.
> Roger Gallardo
> Technical Advisor
> Laguna Clay Co. CA
Roger,
Good points but one correction. Barium can and does exist in a pure
state. It's a silvery metal which oxidizes in air and forms a Barium
Oxide white powder.
Paul
--
Paul J. Monaghan email: paul@web2u.com
WEB2U Productions --- http://www.web2u.com
The "COOLEST" Site on the WEB
"The Computer Secrets are hidden at www.web2u.com/secret"
Ron Roy on mon 17 mar 97
>----------------------------Original message----------------------------
>Can someone please tell us what barium compound is being released
>with your testing. This is important to determine toxicity of the
>compound. An example: barium carbonate is toxic; barium sulphate is
>non-toxic. This is what you drink when you have your stomach
>x-rayed.
>Almost all forms of barium compounds are non-toxic. Another example
>is a frit containing barium. Some people are saying that because a frit
>contains barium, it is toxic, just because it is listed as barium.
>This is false. The barium in a frit is a barium compound and is
>non-toxic. Barium cannot exist as an element. It must be in
>combination with another material.
Where is it written that all Barium frits are safe? Where does it say all
compounds are none toxic? Where does it say that all glazes made with frits
are durable?
When Barium ions get into your body the results are predictable - if enough
get in. These ions are released from certain compounds like Barium
Carbonate and Barium Chloride because these compounds are slightly soluble.
When Barium ions are leached out of glazes or frits the same thing can
happen. Saying that all Barium frits are safe is like saying all Lead frits
are safe. How we test frits and glazes is by subjecting them a standard
acid test - the kind of tests used to determine the safety of dinnerware.
Saying a glaze, made with a frit containing Barium (or any other toxic
material,) is safe does not take into account the changes in the "glass "
occurring during firing. It does not take into account the amount of Barium
there is in frit. If that glaze does not have enough silica or alumina then
there is reason to be concerned. If certain oxides are oversupplied again
we have a less than durable glass. See article in Ceramics Technical -
issue #3 - by Janet DeBoos. Certain of the oxides we use promote solubility
in a glaze like Copper and Sodium.
We have to realize that all glazes leach. The real questions are: what is
coming out, is it harmful, and how much is coming out.
In all of Janets tested glazes there was some release - a few gave up only
0.02 parts per million - but they all gave up some after being in 4% acetic
acid for 24 hours at a temperature of 24C.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Ric Swenson on tue 18 mar 97
Not any kind of expert but here goes my $00.02
Wouldn't it be nice if common sense were common?
Barium release from glazes should never occur in amounts that would harm
anyone....Lead is a different story...there are many elements that are more
dangerous than Barium.. Cadmium, Celenium, Vanadium, Strontium et
al....The dust of ANYTHING is NOT GOOD FOR YOUR LUNGS!
Come on folks...be careful with ALL dusty materials...be especially
watchful of vapors from Salt kilns...sodium chloride...soda ash or sodium
bicarb.......stand away a few feet...use a L O N G handled scoop to put in
the salt...design the kiln so you can add the salt in an area of the
firebox that makes it easy to "dump" into...without endangering your
health....be mindful that a long term exposure as well as a short term
exposure can hurt you.
Barium, as I see it, is a red Herring...I think you will have trouble
finding a case of Barium poisoning in the USA ...or any where else...(look
in LANCET a LONG time ago for an example of a Pakistani chef in WW II, who
didn't speak enough English..used Barium INSTEAD of FLOUR in biscuits and
made his whole battalion ill for a few days.....one elderly officer died
too. This was a massive over dose of barium...ingested into the environment
of the human stomach...water...acid...all that cocktail of liquid to break
down materials)....The truth is that Barium is NOT VERY SOLUBLE...therefore
it is to be respected....but not feared... ( Barium Sulfate used in the
X-Ray drink is very safe...Barium Carbonate and Barium Oxide ought to be
respected more.
Further, It is very unlikely that barium glazes that have been "properly
fired" into a glassy matrix.... will leach enough Barium to make anyone
sick...but why take the chance? fire your pottery properly...just in
case....
Same with lead....it is MUCH more dangerous (especially to young children)
So I would NOT even have it around....BUT it can be used safely and fired
safely and used safely IF you know what you are doing. If you don't know
what you are doing....do something else.
Barium is not a very dusty material...but it can get on your hands....don't
smoke and WASH YOUR HANDS!
Fritting a compound ( melting it and quenching it in water...) makes it
LESS soluble....not UN-SOLUBLE just less soluble. Safer to use...but not
"SAFE" to breath in dust or use as salad dressing....
I have probably started a flame here, but...come on folks worry about real
hazards...there are plenty to go around.
My advice is to respect all chemicals and dusts. Use common sense. and
keep a sense of humor....( What do you do with 56 dead protons? ....Barium
!)
Credit that little humor to Anne Skinner, Chemist at Williams College with
who I exchanged Barium info about this morning and last night.
Ric Swenson, Bennington, Vermont
thoughts expressed are my own.
Keep potting folks..Safely!
but
"never try to be anything you can't spell"
>----------------------------Original message----------------------------
>>----------------------------Original message----------------------------
>>Can someone please tell us what barium compound is being released
>>with your testing. This is important to determine toxicity of the
>>compound. An example: barium carbonate is toxic; barium sulphate is
>>non-toxic. This is what you drink when you have your stomach
>>x-rayed.
>>Almost all forms of barium compounds are non-toxic. Another example
>>is a frit containing barium. Some people are saying that because a frit
>>contains barium, it is toxic, just because it is listed as barium.
>>This is false. The barium in a frit is a barium compound and is
>>non-toxic. Barium cannot exist as an element. It must be in
>>combination with another material.
>
>Where is it written that all Barium frits are safe? Where does it say all
>compounds are none toxic? Where does it say that all glazes made with frits
>are durable?
>
>When Barium ions get into your body the results are predictable - if enough
>get in. These ions are released from certain compounds like Barium
>Carbonate and Barium Chloride because these compounds are slightly soluble.
>When Barium ions are leached out of glazes or frits the same thing can
>happen. Saying that all Barium frits are safe is like saying all Lead frits
>are safe. How we test frits and glazes is by subjecting them a standard
>acid test - the kind of tests used to determine the safety of dinnerware.
>Saying a glaze, made with a frit containing Barium (or any other toxic
>material,) is safe does not take into account the changes in the "glass "
>occurring during firing. It does not take into account the amount of Barium
>there is in frit. If that glaze does not have enough silica or alumina then
>there is reason to be concerned. If certain oxides are oversupplied again
>we have a less than durable glass. See article in Ceramics Technical -
>issue #3 - by Janet DeBoos. Certain of the oxides we use promote solubility
>in a glaze like Copper and Sodium.
>We have to realize that all glazes leach. The real questions are: what is
>coming out, is it harmful, and how much is coming out.
>
>In all of Janets tested glazes there was some release - a few gave up only
>0.02 parts per million - but they all gave up some after being in 4% acetic
>acid for 24 hours at a temperature of 24C.
>
>Ron Roy
>Toronto, Canada
>Evenings, call 416 439 2621
>Fax, 416 438 7849
Evan Dresel on tue 18 mar 97
At 11:26 AM 3-16-97 EST, you wrote:
>----------------------------Original message----------------------------
>Roger Gallardo wrote:
>>
>> ----------------------------Original message----------------------------
>> Can someone please tell us what barium compound is being released
>> with your testing. This is important to determine toxicity of the
>> compound. An example: barium carbonate is toxic; barium sulphate is
>> non-toxic. This is what you drink when you have your stomach
>> x-rayed.
snip
>> Roger Gallardo
>> Technical Advisor
>> Laguna Clay Co. CA
>
>
>Roger,
>
>Good points but one correction. Barium can and does exist in a pure
>state. It's a silvery metal which oxidizes in air and forms a Barium
>Oxide white powder.
>
>Paul
>
>
>--
>Paul J. Monaghan email: paul@web2u.com
>
I have to disagree a bit here. When you do a leach test, you are putting
the barium into solution. In that case I expect you will only see Ba+2
ions. These will be charge ballanced by some negatively charged ion like
Cl- or acetate, but the barium will almost certainly be absorbable by the
body. I suppose you could get some barium-acetate complexes formed but I
don't think that will make much difference. (Generally acetic acid is used
in the leach tests I am familiar with, but I don't know the procedure for
testing ceramics).
The reason barium sulfate is non toxic is that it is extremely insoluable,
even in acid. Barium chloride is extremely soluble and is quite deadly.
This is also why I suspect barium carbonate is not as toxic as people make
out -- it is quite insoluble except under highly acidic conditions and even
then, I belive it disolves very slowly. The handbook of dangerous materials
that I have access to basically uses the information on barium chloride
toxicity in stating barium carbonate toxicity, and I suspect that is not
valid. But I haven't done the tests and wouldn't jump to conclusions. I
just want to suggest the statements about toxicity aren't always supported
by good data.
Anyway, you can't really deal with the leaching data the same way you deal
with a solid compound. Ideally your leach test should mimic the release of
chemicals that would occur in actual use. In practice it will tend to use a
somewhat more aggressive leaching agent to be safe. How about a tomato
sauce leach to be realistic?
While I'm on the subject, I also wonder about the long term release vs the
initial release in a test on a new surface. Typically the initial release
will be higher and then decline as the surface becomes depleted in the
chemical. Also the glaze surface may be more unstable or have a slightly
different composition. It's a tough problem, but important if you are
really concerned with long term exposure.
-- Evan Dresel who couldn't make it across the mountains to an embroidery
exhibit because of the snow.
jason elfert on fri 21 mar 97
i have been following the barium discussion, first with suprise and now
with a combination of aprehension, confusion and a degree of sadness. i
have two glazes that i am very fond of that contain barium. i was aware
that barium was "toxic in raw form", as my suppliers catalogue states. my
storage containers are marked with the appropriate skull and crossbones so
that i'll be reminded as i reach for them to be particulary cautious. now
i hear that that wasn"t enough. now i feel that aprehension.
in the discourse on this material there have been repeated references to
firing temperatures, silica to barium ratios and "proper" firing techniques
and so on.now i begin to feel confused.
my glazes have been reliable friends for years. i've made some lovely
pieces with them. many of these pieces have gone to friends and
family...and many to total strangers. how am i to feel about "prolonged
exposure". do i issue a recall? what about the pieces i'll never be able
to track down. do i have to lay awake nights worring that some poor couple
is serving tomatoe bisque in the white bowls they love?
i fire cone 10 reduction with propane. there is always some variation
within the kiln. the following are my glazes.
tapioca
kona f-4 spar 17.5
custer spar 21.0
ball clay 10.0
flint (325 mesh) 16.0
barium carb. 12.5
whiting 8.7
dolomite 6.0
zircopax 7.5
copper red
neph. sy. 35
whiting 16
zinc 5
barium carb. 8
flint (325 mesh) 25
tin oxide 4
copper carb. 2
i'll find a new white....but would it be sufficient to substitute strontium
in the copper red? i hate to loose this glaze.
thanks, linda elfert
June Perry on sat 22 mar 97
Dear Linda:
Take the amount of barium in your glaze and multiply it by 75% and that will
give you the amount of strontium to substitute. So in the Tapioca glaze you
would substitute 9.38 Strontium carb for the barium and in your copper red
glaze you would substitute 6 Strontium for the barium. The only way you will
know if it works to your satisfaction is by making up at least a 200 gram
test batch of each and firing them in your regular glaze firings.
Regards,
June
Ric Swenson on sat 22 mar 97
REPLY________
Keep following the debate....
I feel there is too much concern about Barium in glazes...it is insoluble
in water and mildly acidic "food" exposures... most glaze formulations in
MY OPINION... I also have used barium in glazes.... for thirty years. I
agree that there should be caution and testing and some concern...but just
because some one poisons a relative with Barium Nitrate is no real to stop
using Barium Carbonate in glazes or in clay to prevent scumming...in
terracotta.
I am not a chemist and no expert in all forms of Barium...so remember as I
said when I first entered this foray....My opinion was formulated when I
read up on Barium in 1980s at Dartmouth Med School Libary..I could find
VERY few examples of Barium incidents...those I did find involved humans
becoming sick after ingesting massive amounts of Barium (in the form of rat
poison). none in pottery venue....Maybe there has been a lot of new
investigation into Barium....Maybe I should be more concerned...BUT when
someone just states to give me undocumented horror stories...I want to see
the proof....read for myself...use my common sense and the training that I
have had...to make my own judgements.
Keep watching and reading...maybe we will get to the bottom of this mystery
soon...
Opinions my own. Let's hear from people with practical test
data...practical dinnerware studies that doesn't involve test rats being
given twice their body weight in Barium cocktails...leached in pure
acid...daily for a year. Dust is not good for your lungs...any
dust...especially heavy metals....silica, alumina...long term exposes can
be life thresatening....wear a dust mask....INGESTION of BARIUM from
dinnerware and any harm that "could" cause is what the issue should focus
on, as far as I am concerned...
I always thought Barium was a non-issue...if it is truly not a problem,
lets talk about something more real...or settle the issue and ban Barium
use IF that is what ought to happen...?
Thanks,
Ric Swenson, Bennington, VT
>----------------------------Original message----------------------------
>i have been following the barium discussion, first with suprise and now
>with a combination of aprehension, confusion and a degree of sadness. i
>have two glazes that i am very fond of that contain barium. i was aware
>that barium was "toxic in raw form", as my suppliers catalogue states. my
>storage containers are marked with the appropriate skull and crossbones so
>that i'll be reminded as i reach for them to be particulary cautious. now
>i hear that that wasn"t enough. now i feel that aprehension.
>in the discourse on this material there have been repeated references to
>firing temperatures, silica to barium ratios and "proper" firing techniques
>and so on.now i begin to feel confused.
>my glazes have been reliable friends for years. i've made some lovely
>pieces with them. many of these pieces have gone to friends and
>family...and many to total strangers. how am i to feel about "prolonged
>exposure". do i issue a recall? what about the pieces i'll never be able
>to track down. do i have to lay awake nights worring that some poor couple
>is serving tomatoe bisque in the white bowls they love?
>i fire cone 10 reduction with propane. there is always some variation
>within the kiln. the following are my glazes.
>tapioca
>
>kona f-4 spar 17.5
>custer spar 21.0
>ball clay 10.0
>flint (325 mesh) 16.0
>barium carb. 12.5
>whiting 8.7
>dolomite 6.0
>zircopax 7.5
>
>
>copper red
>
>neph. sy. 35
>whiting 16
>zinc 5
>barium carb. 8
>flint (325 mesh) 25
>tin oxide 4
>copper carb. 2
>
>i'll find a new white....but would it be sufficient to substitute strontium
>in the copper red? i hate to loose this glaze.
>
>thanks, linda elfert
Monona Rossol on sat 22 mar 97
Excellent post, Bill Walker!!!
> A friend developed this beautiful purple glaze that contained barium
> and wanted to know if it was safe to use on dinnerware, so I had it
> tested. The result was that after sitting overnight filled with 4%
> acetic acid, the purple glaze turned PINK. I think that the chemist
> reported that the Ba++ level in the acid was off the scale. So if
> you visit my friend's studio there is this beautiful cup on display
> with a purple rim and a pink inside. The chemist's report is displayed
> with the cup.
> Someone asked if the amount of barium stays the same with repeated
> use, and the answer is no. The accessible barium all gets leached
> out after a while,.....<
Not actually. The barium leaching will slow down but not stop because the
rest of the glaze is also solubilizing and new surface is slowly being
exposed. ANd when this surface is subject to scrubbing, scratching or
abrading, the exposure of fresh barium rich surfaces is occurs again.
>..... which brings me to the sad story of the couple
> on the west coast (I think) who had these beautiful coffee cups.
> The cups had a lead glaze, and the lead leached out into their coffee.
> But the coffee stained the cups and when they scrubbed to get rid of
> stains they scrubbed off the lead-depleted glaze and exposed more
> leachable lead. At least one of them suffered from rather serious
> lead poisoning. <
Being a lousy housekeeper has its advantages! But any process that
alters the glaze surface can increase leaching in any glaze. This is why the
commercial china industry is very good about developing surfaces that will
resist abrasive cleansers, very hot dish washers, strongly alkaline soaps
(which also can attack glaze surfaces--it ain't just acids), and so on.
Monona Rossol, industrial hygienist
Arts, Crafts and Theater Safety
181 Thompson St., # 23
New York, NY 10012-2586 212/777-0062
http://www.caseweb.com/acts/
Lauren BAll on sun 23 mar 97
I've been following this thread for a while and just wonder about some
obvious alternatives. Why not double glaze. Use any glaze you want,
fire. Then put on a nice thick coat of a clear non-toxic glaze over the
top and refire. If the last glaze matures at a lower temperature, I
would think it should protect us from the hazards. Please comment.
Lauren
Ron Roy on mon 24 mar 97
>----------------------------Original message----------------------------
>i fire cone 10 reduction with propane. there is always some variation
>within the kiln. the following are my glazes.
>tapioca
>
>kona f-4 spar 17.5
>custer spar 21.0
>ball clay 10.0
>flint (325 mesh) 16.0
>barium carb. 12.5
>whiting 8.7
>dolomite 6.0
>zircopax 7.5
>thanks, linda elfert
I have done some revisions for Linda and asked her to let me post them to
ClayArt and she most graciously agreed.
A short preamble. Barium serves almost the same function as Calcium would
in a glaze of this type so for the first glaze I simply replaced the Barium
Carb with Whiting. It is the same glaze on a molecular level with a small
addition of silica to make it more durable and to lower the expansion which
was a bit high. By the way you will probably find your Barium costs 5 times
what Calcium costs - so if these 3 glazes are the same looking then #1 is
the least expensive.
#2 is essentially the same glaze using Strontium Carb and Whiting to
replace the Barium. Many of the glaze books in my library point out that
even small amounts of Strontium increase melt, make glazes harder and lower
expansion (compared to Barium). It would be more expensive to make because
Strontium is more expensive than Barium. Using both Strontium and Whiting
to replace the Barium will probably make this version about the same cost
as the original.
#3 I have replaced all the Barium with Strontium - more expensive and
probably not any advantage.
Test with a 500 gram batch first - there is no guarantee with this set. If
any of you do test this glaze I would appreciate you comments and
observations.
Original Glaze -Tapioca
17.5 F4 spar
21.0 Custer
10.0 Ball clay
16.0 Silica
12.5 Barium Carb.
8.7 Whiting
6.0 Dolomite
7.5 Zircopax
99.20 Total
8.67 Ratio
Revision A
22.0 F4 Spar
22.0 Custer or G200 spar
11.0 Ball clay ( I used OM4) but most will do about the same thing.
20.0 Silica
18.0 Whiting
6.0 Dolomite
8.5 Zircopax
108.5 Total
8.90 Ratio
Revision B
22.5 F4 Spar
22.5 Custer or G200 spar
11.0 Ball clay
20.0 Silica
4.0 Strontium Carb.
15.0 Whiting
6.0 Dolomite
8.5 Zircopax
108.5 Total
8.94 Ratio
Revision C
21.5 F4 Spar
21.5 Custer or G200 spar
11.0 Ball clay
19.5 Silica
9.5 Strontium Carb.
11.0 Whiting
6.0 Dolomite
8.5 Zircopax
108.5 Total
8.91 Ratio
If anyone has any questions about this - ask away.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
RJMOORE2 on sat 29 mar 97
What about the barium mixture paitients are given in hospitals prior to GI
tests?
I would think this exposure is much more than what one would get from a leaching
pot, even after using the pot many times.
Someone else may be able to enlighten the group more extensively in this matter.
rjmoore
______________________________ Reply Separator _________________________________
Subject: Re: barium research
Author: Ceramic Arts Discussion List at SMTP-Gateway
Date: 3/27/97 6:53 AM
----------------------------Original message----------------------------
REPLY________
Keep following the debate....
I feel there is too much concern about Barium in glazes...it is insoluble
in water and mildly acidic "food" exposures... most glaze formulations in
MY OPINION... I also have used barium in glazes.... for thirty years. I
agree that there should be caution and testing and some concern...but just
because some one poisons a relative with Barium Nitrate is no real to stop
using Barium Carbonate in glazes or in clay to prevent scumming...in
terracotta.
I am not a chemist and no expert in all forms of Barium...so remember as I
said when I first entered this foray....My opinion was formulated when I
read up on Barium in 1980s at Dartmouth Med School Libary..I could find VERY
few examples of Barium incidents...those I did find involved humans becoming
sick after ingesting massive amounts of Barium (in the form of rat poison).
none in pottery venue....Maybe there has been a lot of new investigation
into Barium....Maybe I should be more concerned...BUT when someone just
states to give me undocumented horror stories...I want to see the
proof....read for myself...use my common sense and the training that I have
had...to make my own judgements.
Keep watching and reading...maybe we will get to the bottom of this mystery
soon...
Opinions my own. Let's hear from people with practical test
data...practical dinnerware studies that doesn't involve test rats being
given twice their body weight in Barium cocktails...leached in pure
acid...daily for a year. Dust is not good for your lungs...any
dust...especially heavy metals....silica, alumina...long term exposes can
be life thresatening....wear a dust mask....INGESTION of BARIUM from
dinnerware and any harm that "could" cause is what the issue should focus
on, as far as I am concerned...
I always thought Barium was a non-issue...if it is truly not a problem,
lets talk about something more real...or settle the issue and ban Barium
use IF that is what ought to happen...?
Thanks,
Ric Swenson, Bennington, VT
>----------------------------Original message---------------------------- >i
have been following the barium discussion, first with suprise and now >with
a combination of aprehension, confusion and a degree of sadness. i >have
two glazes that i am very fond of that contain barium. i was aware >that
barium was "toxic in raw form", as my suppliers catalogue states. my
>storage containers are marked with the appropriate skull and crossbones so
>that i'll be reminded as i reach for them to be particulary cautious. now
>i hear that that wasn"t enough. now i feel that aprehension.
>in the discourse on this material there have been repeated references to
>firing temperatures, silica to barium ratios and "proper" firing techniques
>and so on.now i begin to feel confused.
>my glazes have been reliable friends for years. i've made some lovely
>pieces with them. many of these pieces have gone to friends and
>family...and many to total strangers. how am i to feel about "prolonged
>exposure". do i issue a recall? what about the pieces i'll never be able
>to track down. do i have to lay awake nights worring that some poor couple
>is serving tomatoe bisque in the white bowls they love?
>i fire cone 10 reduction with propane. there is always some variation
>within the kiln. the following are my glazes.
>tapioca
>
>kona f-4 spar 17.5
>custer spar 21.0
>ball clay 10.0
>flint (325 mesh) 16.0
>barium carb. 12.5
>whiting 8.7
>dolomite 6.0
>zircopax 7.5
>
>
>copper red
>
>neph. sy. 35
>whiting 16
>zinc 5
>barium carb. 8
>flint (325 mesh) 25
>tin oxide 4
>copper carb. 2
>
>i'll find a new white....but would it be sufficient to substitute strontium
>in the copper red? i hate to loose this glaze.
>
>thanks, linda elfert
Paul Monaghan on sun 30 mar 97
RJMOORE2 wrote:
>
> ----------------------------Original message----------------------------
>
> What about the barium mixture paitients are given in hospitals prior to GI
> tests?
> I would think this exposure is much more than what one would get from a leachi
> pot, even after using the pot many times.
RJ,
the barium salts used for GI series are Barium Sulphate, non-toxic and
virtually non-absorbable. However, almost any substance left in the GI
track long enough can have some materials leached if only in the parts
per billion (ppb) range. The Barium is pretty well clear of the system
in 12 hours or less.
The thread on toxic glazes, Barium etc tends many times to get blown out
of proportion. We must always look at the level of toxicity, the
concentration in the body and the environmental length of exposure.
Substances such as Beryllium are extremely toxic and cause cancer.
Therefore, the exposure limit must be held as close to zero as possible.
However, substances such as Lead and Barium are not carcinogenic but
will cause longterm health effects from continued longterm exposure even
at reduced exposure levels. So the prudent approach is to reduce the
levels in any one exposure and reduce the exposure time.
So what does all this mean? If you have a non-carcinogenic,
non-poisonous material in a glaze which may leach out parts per billion
from acidic foods than you might want to limit your longterm exposure.
In other words don't suck soup 24/7 out of that same cup!! You'll be
OK. It boggles my mind that people get so wrapped around the axle about
really small hazards and don't even notice or address the big ones.
If you knew what you are breathing and drinking in typical municipal air
and water you'd crook. If you knew what was allowed to be in foods -
such as number of rat hairs and animal parts in ketchup, peanut butter,
etc you might give up eating!! If you have ever been in commercial
kitchens and saw how the food was prepped you might never again eat in
restaurants.
So be reasonably careful in all endeavors but don't get so wrapped up on
all the hazards that you stop living. I got a really big kick from the
person on Clayart complaining about Arthritis, Carpal tunnel, Backache,
Tendonitis, etc. So much so that they said it hurt to get up and empty
the ash tray - DA! This person is probably losing sleep over Barium
leaching out of some pottery.
Don't Worry! Be Happy!!
Cheers,
Paul :-)
--
Paul J. Monaghan email: paul@web2u.com
WEB2U Productions --- http://www.web2u.com
The "COOLEST" Site on the WEB
"The Computer Secrets are hidden at www.web2u.com/secret"
Ron Roy on sun 30 mar 97
>...but just because some one poisons a relative with Barium Nitrate is no
>real to >stop using Barium Carbonate in glazes
Missed to point completely: The other part of the story was - she almost
got away with it because the effects of Barium poisoning can be mistaken
for a heart attack."
As I have pointed out before - normal healthy adults are not at as much
risk as people with heart trouble, the young and the unborn. On top of
that, as I have said before, there are other fluxes that work just as well
as Barium for the type of glazes which should be used for lining pots.
Because there are so many of use without the proper training about the
technical aspects of our craft - we choose glazes by how they look and if
we have the materials to make them. The names attached to glazes become the
reason for trying them. Our inability to formulate our glazes has resulted
in an industry that provides glazes for us. In most cases those people who
published these glazes suffered from the same ignorance that is so common
in our community. There are signs that we are begining to overcome this
situation. I have even seen a book that has no Barium glazes in it.
When we see people behaving in a responsible manner we must support them.
Reward those authors that take a responsible attitude. It is why I
encouraged every one to support Janet DeBoos in her research on Barium
published in Ceramic Technical - issue #3. She is an educator who has used
the resources of her institution to do much needed research.
Industry is not going to help - unless they see an opportunity for profit
or at least some positive PR.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
ronroy@astral.magic.ca
Karen Gringhuis on sun 30 mar 97
RJ - my understanding based solely on hearsay is that for x-rays,
one drinks barium SULPHATE. Ask Toni Hall here on the list.
Karen Gringhuis
CDANIELLE on mon 31 mar 97
Ron Roy wrote:
>
> ----------------------------Original message----------------------------
>I have even seen a book that has no Barium glazes in it.
> Ron Roy
> Toronto, Canada
> Evenings, call 416 439 2621
> Fax, 416 438 7849
> ronroy@astral.magic.ca
What is the name of this book? Or any other good book on glazes, for
that matter does anyone know of a good book that goes into the toxic
aspects of glaze materials in their fired state?
Gabe Thomas
Springfield OR
cdanielle@prodigy.net
Monona Rossol on mon 7 apr 97
Paul Monaghan wrote:
> So what does all this mean? If you have a non-carcinogenic,
> non-poisonous material in a glaze which may leach out parts per billion
> from acidic foods than you might want to limit your longterm exposure.
> In other words don't suck soup 24/7 out of that same cup!! <
Basically I agree except for three points.
1. Chronically toxic substances are not "non-poisonous," they are just
"non-acutely poisonous." Big difference.
2. Barium and stuff is not leaching out in parts per billion--but in parts
per million. THose three decimal points are important.
3. THe fact that potters know that you shouldn't drink out of the same cup
or eat out of the same bowl every day is of no help to consumers---unless we
make sure they are all educated about this problem. And have you ever tried
to get a favorite cup away from a kid?
> If you knew what you are breathing and drinking in typical municipal air
> and water you'd crook. If you knew what was allowed to be in foods -
> such as number of rat hairs and animal parts in ketchup, peanut butter,
> etc you might give up eating!! If you have ever been in commercial
> kitchens and saw how the food was prepped you might never again eat in
> restaurants. <
The municiple water standards--as far as metals go--are not too bad. I use
the EPA standards for reference to glaze leaching. But we are seeing more
microorganisms and pesticides creeping into our water.
About the food, you are right. I managed an upper east side NYC "good"
restaurant for a year and a half. What I saw there has caused me to avoid
eating out when possible ever since. But food, air, and all these other
sources of pollution are reasons for being *more* careful of what we can
control rather than *less* careful. It is the total exposure to all this
s**t that makes the problem worse.
> I got a really big kick from the person on Clayart complaining about
> Arthritis, Carpal tunnel, Backache, Tendonitis, etc. So much so that they
> said it hurt to get up and empty the ash tray - DA! <
Here I agree completely. If I lectured on health and safety and then lit up,
I would be showing by example that I didn't really believe a word of what I
said.
Monona Rossol, industrial hygienist
Arts, Crafts and Theater Safety
181 Thompson St., # 23
New York, NY 10012-2586 212/777-0062
http://www.caseweb.com/acts/
hm9 on mon 7 apr 97
I have long thought that a great deal of information both good and bad was
being exchanged on clayart. With my retirement from the University of
Maryland I will now have the time and plan on developing some papers dealing
with these questions such as barium or the use of a salt kiln. I propose
using the clayart archives as well as my printout of the daily postings to
develop this series and I will give credit to all who contributed ideas.
In respons to Jason's elfert questions about his glazes I would like to
suggest that he do some tri axel tests in which three galzes are employed,
his original formuals and two subsititutions, one with 12.5 grams of
lithium, and the other with 12.5 grams of magnesium.
by doing the triaxel analysis he will be able to determine the range of
effects of matt gales without the barium or at least with a greatly reduced
amount of the barium
Harold J. McWHINNIE
Email:Harold_J_McWHINNIE@umail.umd.edu (hm9)
Phone:53125
Hodaka Hasebe on tue 8 apr 97
I have been searching this subject in the Internet for a couple of weeks.
Here is one makes me interested in. This is a petetion (which is denied,
unfortunately), however, contents of this texts explains a wide range of
things regarding to this subject. You can find it at
http://www.epa.gov/docs/fedrgstr/EPA-WASTE/1997/January/Day-03/pr-808DIR/pr-
808.html
Is there any condition set for annual consumption of barium for the EPA's
standard for 2ppm used with the specific test method? I assume this 2ppm
for test guidline represents some kind of condition (such as, 2ppm EPA
standard represent annual average consumption of x mg of barium) to
simulate long term effects. I seached for several hours on the Net, but
found only 2ppm.
Thanks
hasebeh@vivanet.com
Evan Dresel on thu 10 apr 97
At 12:20 PM 4-7-97 EDT, Monona wrote:
>----------------------------Original message----------------------------
>
>
>The municiple water standards--as far as metals go--are not too bad. I use
>the EPA standards for reference to glaze leaching. But we are seeing more
>microorganisms and pesticides creeping into our water.
>
I sort of agree and sort of disagree. The EPA drinking water standards are
a useful reference but really only give you a relative sense of the hazards.
I use them myself as a reference for assessing the problem with contaminated
water that no one is drinking. But I think it's worth looking at what is
behind the standards. For drinking water the usual assumption is that a
person consumes 20 L a day for 70 years. The cumulative dose or exposure or
risk or however you measure the "danger" is much higher than any exposure I
can invision from leaching of ceramics. Yes, it is good to make
conservative assumptions, but don't forget that the drinking water standards
**usually** make conservative assumptions so you are multiplying that by a
large factor.
There are chemicals for which the drinking water standards are at least less
cautious, or even allow a greater risk than usual. The best example is for
trihalomethanes (eg chloroform). The trouble is, you form chloroform when
you chlorinate watersupplies containing traces of organic matter. In this
case the EPA decided, reasonably, that the risk from not chlorinating the
water is greater than the risk from the trihalomethane. In other cases it
is just too expensive to treat the water.
I don't think we are really seeing more microorganisms in water supplies
these days. The level of testing of supplies has increased quite a bit in
the last few decades and treatment technology is better. Ok, Milwalkee's
recent outbreak indicates that there still are some significant problems,
but I don't think new ones. As for pesticides, I think they are generally
less significant than they are made out to be in water supplies. Far more
significant in the air -- at least in rural and suburban areas.
I don't want to spread rumors, but if I remember correctly, EPA increased
the standard for barium from an interim value of 1 mg/L to 2 mg/L but had
originally proposed a final standard of 4 mg/L. The 2 was a compromise --
not exactly scientific.
>
>Monona Rossol, industrial hygienist
>Arts, Crafts and Theater Safety
>181 Thompson St., # 23
>New York, NY 10012-2586 212/777-0062
>
>http://www.caseweb.com/acts/
>
-- Evan Dresel
pedresel@revolution.3-cities.com
Fixing fences and irrigation and hoping all of you in the Dakotas,
Minnesota, and Manitoba are staying dry and warm.
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