Shula on wed 7 apr 10
In the past, I have avoided barium in glazes like the plague. However, I bo=
ught a book on dry glazes and I have fallen in love with those beautiful ba=
rium blue glazes. I'm thinking of creating some sculptural forms and using =
barium glazes. But before I do, I want to know whether firing barium contai=
ning glazes in my kiln will negatively effect my kiln and the functional pi=
eces I subsequently fire in the kiln (L&L fired outside with a vent). I rem=
ember reading that if you fire lead containing glazes, the lead contaminate=
s the kiln and may effect pieces that are subsequently fired in the kiln. D=
oes barium do the same thing? Are there any other chemicals that contaminat=
e the kiln and could negatively impact subsequent firings of functional war=
e?
By the way, I do use a respirator and gloves when weighing and mixing glaze=
s and spray glazes outside. I have lots of allergies and asthma and don't w=
ant to aggravate either.
Thanks
Shula
Desert Hot Springs, California USA
Shula
Desert Hot Springs, California USA
www.claymystique.etsy.com
Fredrick Paget on thu 8 apr 10
There are a lot of elements that will vaporize at kiln temperatures.
Lead , mercury, niobium are ones I have had experience with.
Lead glazes can not be used above cone 1 or so as it vaporizes the
lead. Probably a couple of good cone 10 firings would clean the kiln.
I once fired some scrap molybdenum that contained niobium scrap also
and it did contaminate the kiln for several firings. It was evidenced
by the way the niobium spoiled the glazes on the side of the kiln
where the niobium was placed in the original firing.
Several firings to crystal glaze cone 10 got rid of it.
Mercury is bad too and easily vaporized but we do not use it in
ordinary art ceramics.
I won't bore you by going through the entire periodic table but there
are other cases I am sure.
Keep asking questions, Potters need to know what they are doing.
Fred Paget
Twin Dragon Studio
Mill Valley, CA, USA
fredrick@well.com>
Charter Member Potters Council
>I remember reading that if you fire lead containing glazes, the lead
>contaminates the kiln and may effect pieces that are subsequently
>fired in the kiln. Does barium do the same thing? Are there any
>other chemicals that contaminate the kiln and could negatively
>impact subsequent firings of functional ware?
>
>
>Shula
--
Fredrick Paget on thu 8 apr 10
I forgot to answer the barium part.
I looked up barium compounds in the Handbook of Chemistry and Physics
which lists these things about chemicals such as boiling point in deg
C. Barium carbonate decomposes to the oxide at around 1450 C. The
oxide has a boiling point over 2000 C. (3652 F ). So I think you are
safe from vaporizing it.
Fred
>In the past, I have avoided barium in glazes like the plague.
>However, I bought a book on dry glazes and I have fallen in love
>with those beautiful barium blue glazes. I'm thinking of creating
>some sculptural forms and using barium glazes. But before I do, I
>want to know whether firing barium containing glazes in my kiln will
>negatively effect my kiln and the functional pieces I subsequently
>fire in the kiln (L&L fired outside with a vent). I remember reading
>that if you fire lead containing glazes, the lead contaminates the
>kiln and may effect pieces that are subsequently fired in the kiln.
>Does barium do the same thing?
>Shula
>Desert Hot Springs, California USA
>www.claymystique.etsy.com
--
Vince Pitelka on thu 8 apr 10
Shula wrote:
"In the past, I have avoided barium in glazes like the plague. However, =3D
I bought a book on dry glazes and I have fallen in love with those =3D
beautiful barium blue glazes. I'm thinking of creating some sculptural =3D
forms and using barium glazes. But before I do, I want to know whether =3D
firing barium containing glazes in my kiln will negatively effect my =3D
kiln and the functional pieces I subsequently fire in the kiln (L&L =3D
fired outside with a vent). I remember reading that if you fire lead =3D
containing glazes, the lead contaminates the kiln and may effect pieces =3D
that are subsequently fired in the kiln. Does barium do the same thing? =3D
Are there any other chemicals that contaminate the kiln and could =3D
negatively impact subsequent firings of functional ware? By the way, I =3D
do use a respirator and gloves when weighing and mixing glazes and spray =
=3D
glazes outside. I have lots of allergies and asthma and don't want to =3D
aggravate either."
Shula -=3D20
I agree with everything that James Freeman said about barium. It is a =3D
very special glaze material, and strontium does not create the same =3D
results. As long as you use it carefully, there is absolutely no reason =
=3D
not to use it in glazes, and it will not adversely affect your kiln or =3D
other ware in any way. Barium matts and semi-matts can be really =3D
magical glazes.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Edouard Bastarache on fri 9 apr 10
Here goes,
1 :
IV. Exprimental Toxicology :
In the case of barium carbonate, the Lethal Dose Fifty (LD 50) is :
- mouse (ingestion) : 200 mg/kg
- rat (ingestion) : 418 mg/kg
which makes it a very toxic chemical by ingestion.
2:
. Foodstuffs provide also barium and the daily human intake has been
estimated to be in the order of 1 mg.
3:
The lethal dose in man varies, according to barium compounds involved,
between 1 and 15 g. by ingestion. Acute intoxications are rare and generall=
y
due to suicidal attempts with the chloride or the carbonate. Some cases of
collective food intoxications were reported, related to food contamination,
and to confusion between carbonate and barium sulphate at the time of
radiological examinations. Barium carbonate having been substituted
accidentally for potato flour during the preparation of sausages, 144 peopl=
e
were poisoned in Israel in 1963. Two patients died.
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://edouardbastarache.blogspot.com/
http://www.flickr.com/photos/30058682@N00/
http://blogsalbertbastarache.blogspot.com/
http://cerampeintures.blogspot.com/
http://perso.wanadoo.fr/smart2000/index.htm
Ric Swenson on fri 9 apr 10
Vince,
I too believe in the matt, beautiful charactaristics of barium in glaze and=
also as a de-scumming agent in terracotta.
Witness the turquioise hippo!
I did a lot of research at Dartmouth Medical School in the 1980s about this=
subject and found almost no evidence of it's harmful effects on potters. =
A few notes on it accidental use in baking in some early British outposts..=
.when it was mistakenly used to bake breads....but that was an anomaly. It=
caused only one death in an elderly and ....not healthy solider.
We continued to use Barium Carbonate as a de -scumming agent in terracotta=
..and they do to this day at Bennington Potters as far as I know.
There is scant evidence of Barium leaching or absorbtion in humans...unless=
ingested in pretty large amounts...this in response to M. Rossenols backle=
ss tirad in her book on safety. My apologies. The science of fear abounds.
It is nothing like the potenial harm of lead...which I avoid and will alway=
s avoid...because of its potential harm to potter and user.
Actually this thread about Barium Carb. goes back to the 1990s.
Heavy metals scare us.
be well,
Ric
"...then fiery expedition be my wing, ..."
-Wm. Shakespeare, RICHARD III, Act IV Scene III
Richard H. ("Ric") Swenson, Teacher,
Office of International Cooperation and Exchange of Jingdezhen Ceramic Inst=
itute,
TaoYang Road, Eastern Suburb, Jingdezhen City.
JiangXi Province, P.R. of China.
Postal code 333001.
Mobile/cellular phone : 86 13767818872
< RicSwenson0823@hotmail.com>
http://www.jci.jx.cn
> Date: Thu, 8 Apr 2010 21:03:27 -0500
> From: vpitelka@DTCCOM.NET
> Subject: Re: toxic chemicals in the kiln - which contaminate the kiln?
> To: Clayart@LSV.CERAMICS.ORG
>
> Shula wrote:
> "In the past, I have avoided barium in glazes like the plague. However, I=
bought a book on dry glazes and I have fallen in love with those beautiful=
barium blue glazes. I'm thinking of creating some sculptural forms and usi=
ng barium glazes. But before I do, I want to know whether firing barium con=
taining glazes in my kiln will negatively effect my kiln and the functional=
pieces I subsequently fire in the kiln (L&L fired outside with a vent). I =
remember reading that if you fire lead containing glazes, the lead contamin=
ates the kiln and may effect pieces that are subsequently fired in the kiln=
. Does barium do the same thing? Are there any other chemicals that contami=
nate the kiln and could negatively impact subsequent firings of functional =
ware? By the way, I do use a respirator and gloves when weighing and mixing=
glazes and spray glazes outside. I have lots of allergies and asthma and d=
on't want to aggravate either."
>
> Shula -
> I agree with everything that James Freeman said about barium. It is a ver=
y special glaze material, and strontium does not create the same results. A=
s long as you use it carefully, there is absolutely no reason not to use it=
in glazes, and it will not adversely affect your kiln or other ware in any=
way. Barium matts and semi-matts can be really magical glazes.
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
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