John Baymore on fri 29 sep 00
So the question is- when we put barium in the clay, are we putting
ourselves at risk for ingesting it through the skin? Is is safe in the
classroom?
Surprised that you didn't get an ONSLAUGHT of responses. Barium carbonat=
e
seems to always be a "hot button" issue. Maybe it has been discussed so
much lately that people just don't want to get into it again so soon .=
=
I would strongly urge you to search the archives....you'll find LOTS of
thoughts on barium carbonate. Check out Monona Rossol's "Keeping Claywor=
k
Safe and Legal" and Dr. Michael McCann's "Artist Beware" books. Also for=
a
completely disenting view from those texts, see Jeff Zamek' Ceramics
Monthly article "Is Barium Carbonate Safe".
As to the archives........ there seem to be two "camps" on all things
health and safety in ceramics...... those who see the glass as half empty=
,
and those who see the glass as half full . =
Unfortunately...... there is little specific research on many of the issu=
es
with which we as handcraft potters are confronted. There is room here fo=
r
some good science to be done (not "potter science"), but potters are such=
an insignificant population that there is no money available to fund the
research. Maybe ACERS could pick up the funding on some of this kind of
long term medical study?????
First off....a little terminology adjustment . "Ingesting" usually
refers to an oral route. Toxins coming through the skin usually are
refered to as being "absorbed". Stuff breathed in is "inhalation". Stuf=
f
contained in a clay body probably is of as much concern through inhalatio=
n
of general studio dusts as it is for possible skin absorbtion issues.
Like most health and saftey questions in ceramics.......... no simple
"black and white" answer. =
The simplest answer from my personal "knowledge base" is ....... MOST
LIKELY it is not a SIGNIFICANT hazard due to the low amount typically
used........ but ............ .........the terms "most likely" and
"significant" are the key words in the prior statement.
How much possible hazard is acceptable? How sure about the risks do you
need to be? Most of us would somewhat agree on the degree and sureness o=
f
hazard from a robber holding a gun at our back and saying "Give me your
wallet". This barium issue is nowhere as clear or severe . You and
your school administration will have to decide that one given the availab=
le
info you can amass. =
Except where health and safety stuff is exactly governed by law (and
sometimes not even then), like US OSHA's airborne PEL's and the US FDA le=
ad
and cadmium ceramic standards, this stuff is never very clear cut. In o=
ur
US society these days, a kid with a swiss army knife in school might be
treated the same as a kid with a switchblade, simply for having a "knife"=
.. =
Yes.... all offer more "risk" than if a cutting device was not present in=
the school. How much risk from a "knife" is OK? Opinions vary. =
("Nah...... THIS is a knife. - Crocodile Dundee )
The frequency of exposure, the intensity, and the duration all come into
play. The relative toxicity of the material is important, it's
bioavailability, and how it enters the body. Genetic predisposition is a=
factor. Other ailments and conditions can create susceptablity to a
toxin's effects. Variables are all over the place. Each can affect the
significance of the risk. All this is difficult to exactly quantify in
studio situations.
Getting more technical ..........
The job of the barium carbonate added to the clay body is to chemically
change the nature of the soluble materials that cause the scumming into
insoluble types. In the process this also changes the barium carbonate t=
o
a less toxic form. Any barium carbonate added in excess of the EXACT
amount needed to tie up the solubles will remain as barium carbonate in t=
he
clay body. This barium carbonate still exhibits it's toxic properties as=
listed on a MSDS. So if you don't want barium carbonate floating around =
at
all in the dust from the clay as well as in the wet plastic clay.........=
..
then you have to get the barium carbonate addition exactly correct.
Are you prepared to do the testing to do this? Or are you going to just
use the "rule of thumb" addition amount? If you use the "rule of thumb"
addition.......... then the barium carbonate in the clay "risk factor"
probably went up a little. How much? Who the heck knows .
The practical approach to this BC addition is to experiment with the
claybody recipe, adding very small increments of barium carbonate until t=
he
scumming issue just stops. In most cases you'll probably find that you a=
re
under 1/4 of one percent dry weight. This addition is easiest done in a
body you mix yourself from dry ingredients. Altering a commercial wet bo=
dy
just introduces a lot more labor to get the BC into the mix in even
distribution. Pain in the butt. =
Keep in mind that batches of clay can vary over time as to the soluble
content. So the necessary barium carbonate addition can vary too.
So........
No definitive, exact "off the shelf" answers to this kind of stuff becaus=
e
there is no extensive hard "handcraft pottery specific" data from which t=
o
evaluate. There is no question that barium carbonate has the POTENTIAL t=
o
be a hazardous material to use....simply reading the federally mandated
MSDS tells you that. However, in practical studio usage......how hazardo=
us
is it? No one has the 20 year medical study of handcraft potters workin=
g
with barium carbonate containing clay to refer to in evaluating risk
factors. Pretty much everything that is available on barium carbonate is=
from industrial studies using the materials under differrent conditions o=
r
for different exposure situations.
In the final analysis, you have to decide given the available information=
,
how you want to deal with this kind of question.
Best,
........................john
PS: My personal approach to these types of questions is that if there i=
s
insufficient data to prove that a material is a hazard, then I also do no=
t
have the proof that it is non-hazardous...... and some educated prudence =
is
probably in order. When it comes to health....a bit cautious rather than=
sorry later.
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752 (s)
800-900-1110 (s)
JBaymore@compuserve.com
John.Baymore@GSD-CO.com
"Earth, Water, and Fire Noborigama Woodfiring Workshop August 18-27,
2000"
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