Tom Fossier on fri 25 apr 03
I am considering using barium, but I wish to read up on its toxicity first.
I would like to know how much quantitative exposure, in what form, over what
period of time, etc, poses a health hazard. Can anyone recommend a book or
website which thoroughly discusses this subject? Even better, can anyone
recommend a book or website which thoroughly discusses the potential
toxicity of all of the commonly used ceramic materials?
Ron Roy on sun 27 apr 03
Monona's book is the best I have found - if you are getting into Barium
make sure the glazes buckets have good lids - if pets drink the water you
will have evidence of it's toxicity - it is used as a rat poison.
Those who work for industry will minimize danger - they have to - part of
thier job.
RR
>I am considering using barium, but I wish to read up on its toxicity first.
>I would like to know how much quantitative exposure, in what form, over what
>period of time, etc, poses a health hazard. Can anyone recommend a book or
>website which thoroughly discusses this subject? Even better, can anyone
>recommend a book or website which thoroughly discusses the potential
>toxicity of all of the commonly used ceramic materials?
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Tony Hansen on sun 27 apr 03
Check the barium carbonate record at www.ceramicmaterials.info.
There is lots of info in the toxicity and article links. Here is
part of it:
Barium carbonate powder is well known as a poisonous substance whereas barium sulfate is insoluble and non-toxic. Barium carbonate performs certain physical and oxide sourcing functions in ceramic glazes and bodies for which substitutes can be either very difficult or expensive to implement. Determining the threat of barium is not as simple as simply saying “all uses of barium are dangerous”. Barium carbonate supplies BaO to glazes which may or may not be soluble in acids that come into contact with the glaze surface. This solubility depends on the chemical balance of the glaze, that is, the degree to which it locks the BaO molecules into the glass structure. In bodies, minute percentages of barium carbonate precipitate soluble salts that cause surface scumming in fired ware and no other material is known to effectively perform this function. Thus discussions of barium toxicity relate to the actual use of the powder in the studio or plant and the degree of solubility of ware made using barium compounds.
Where barium carbonate is employed for chemistry reasons, hazards related to its raw form can be minimized by using a frit that sources barium oxide. This involves doing chemistry calculations to introduce the frit without changing the overall chemistry of the glaze.
Harzards related to the quality of ware produced are not connected to the material sourcing the BaO, but to the availability of BaO ions to solubility. This can be a complex issue and tradeoffs must be considered. Where small percentages are involved, the likelihood of danger is also small if the glaze is balanced (e.g. well melted and having adequate silica and alumina). But at the same time small amounts are likely candidates for substitution with other fluxing oxides without significant effects on physical properties or appearance of the glaze. Where larger amounts are involved successful substitution is much less likely. Crystalline matte surfaces done with barium, for example, often have a character that is difficult to duplicate with other oxides. For example, there are many frits intended for the production of matte glazes that employ BaO as the mechanism. One alternative is to develop a base matte glaze using another mechanism (i.e. high CaO, SrO) and substitute the colorants, opacifiers and variegators into it. The presence of barium is key to the development of certain colors (e.g. barium blue) and substitution of other oxides often will not work.
It is possible to achieve barium-unique effects and still have a glaze that has low solubility. However most would agree to the ethical position that such glazes should not be used on food surfaces without additional leach testing on over and underfired ware. Even then the possibility that a glaze has a fragile chemical balance that protects leachability presents the possibility that small variations in materials could disproportionately increase solubility at times.
For more information, check the article links for the barium carbonate at www.ceramicmaterials.info. These provide detailed toxicity data and information about the use of barium to precipitate soluble salts in clay bodies.
One final note: Barium is considered dangerous when swallowed, however it is much less toxic as dust or in skin contact. The author has worked in a local ceramic industry that has routinely used barium carbonate in tile, brick and pottery bodies for 90 years and the silicosis threat from quartz in the clay has always completely overshadowed toxicity ingestion or inhalation issues surrounding barium.
> I am considering using barium, but I wish to read up on its toxicity first.
> I would like to know how much quantitative exposure, in what form, over what
> period of time, etc, poses a health hazard. Can anyone recommend a book or
> website which thoroughly discusses this subject? Even better, can anyone
> recommend a book or website which thoroughly discusses the potential
> toxicity of all of the commonly used ceramic materials?
========
Tony Hansen
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