John Baymore on fri 11 apr 97
Karl Platt wrote (in part):
.........my experiences making chemical vat lining tiles. The glaze
contained about 4% BaO and the tiles never failed, showed color changes or
spoiled product owing to leaching. These were used ............
............ in the food processing industry.
Karl is a ceramic engineer with a pretty vast knowledge of ceramic
chemistry and many years of experience. He has the scientific
understanding and skills to work with a lot of materials that the average
ceramic artist, production potter, or hobby potter does not. He knows how
to formulate glazes and glass, how to fire them, and how to test them. He
has the ability at a technical level to do the things that we might dream
of.
........... only documented cases of leaching problems (poisoning)
have been with foreign products. Especially rustic stuff from Latin America
where smearing litharge onto a pot passes for glazing in a lot of places.
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I am sure that I will get flamed for this next comment, and I know that
generalizations are dangerous, but this is a key point that I think the
more expert people in the field often miss, coming from the viewpoint of
posessing a vast understanding of the subject.
(My advance apologies to those reading this that DO have a solid technical
background.)
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It is my experience in teaching pretty involved ceramic materials and kiln
courses at the college level and doing technical consulting to potters and
schools since the late 70's, that the VAST majority of people practicing as
(non industrial) potters "out there" in this country (can't say anything
about the rest of the world) have little or no technical understanding of
their materials or processes.
I have a background better than most (thank you Lyle Perkins for setting up
a great department at UMass in the 60's and inspiring me to continue
learning), hence I teach this type of material ("Ceramic Materials" and
"Kiln Design and Operation") to pottery students, ......... but I am FAR
from an engineer. To be honest, I barely feel competent as a "technician".
I have had college level chemistry, basic engineering calculus, and a
college trained potter's preping in ceramic materials science. I have done
a lot of continuing education in the technical area on my own over the
years. Yet, I have only scratched the surface in this field. But as
someone once said ............. "In the land of the blind, the one eyed man
is gifted."
The practice of "........smearing litharge onto a pot passes for glazing in
a lot of places" ........ or its toxicological equivalent passes for
glazing in way too many places IN THIS COUNTRY too as we approach THE 21st
CENTURY. Most potters work at a "macro" level of investigation at
best........ if it looks good, it is good.
Testing of fired products in any way is very uncommon, and chemical testing
is almost unheard of. Even among those who still use lead (and
interestingly, many do......... particularly in "lead-safe" glazes).
Simple pseudo-scientific "molecular" glaze calc is foreign to most, so even
a rudimentary "oxide level" grasp is far away. Many art colleges and
university art departments have dropped their (formerly) required ceramic
technical courses like "Glaze Calc" and "Kiln Design and Operation" (from
the 60's and 70's and early 80's) as the budget squeeze got tighter on the
department. Little information is included in the new texts being
published, and "unstable" formulas continue to be published in books and
magazines without any listed qualifications on usage.
It is this situation that is very worrisome to me.
I agree completely with the statement:
The point is that condemning this or that glaze component as a
matter of
ideology is, well, dumb. i. e. "Barium is BAD"
However, the discussion that goes on within this list and elsewhere is very
important in that it starts many people thinking about what it is that they
do. For many, it is the only source of more "technical" information that
they get. Our schools are NOT teaching much about this. And that is if
the potter even went to a school. Many practicing professionals are self
taught from very basic books and occasional workshops.
So statements from an expert who DOES know how to deal with the more toxic
materials in an appropriate manner, and who DOES know the chemistry
involved are important. Very important. It lets us know what is
accomplishable. These statements also let us know how much we still have
to learn, and hopefully inspire us to LEARN. Or at least question our
assumptions. It helps take us from attention getting generalizations like
"Barium is BAD" toward refinements that allow us to know WHEN barium is not
optimum, and eventually (if we have the timeto studi enough) to how to use
barium effectively and safely.
However, the fact that such a person can make a particular material work,
should not be taken as proof that someone with less knowldege can blithely
be, (and I take a liberty here) "............smearing a glaze containing
40% barium carbonate, 20% lithium carbonate and 6% copper carbonate onto a
pot and pass it off for glazing". This IS the current state of the
situation.
I think Karl is right............ well formulated and fired glazes
containing barium are probably very little hazard to the user.
Particularly when a quality control and testing program is in place to
assure no undue variations in the fired products.
I think Monona is pretty much on track too. The key issue here really is
that there are few who fall outside of engineering and industry that have
the equipment, the knowledge, and the testing tools to do this. Most are
not fully aware of any level of hazard to themselves or others.
So Karl......... keep sharing your technical knowledge on this stuff.
Explain in detail....... give us sources for further research. It helps us
clarify all of the disparate info out there and sort out the wheat from the
chaff. And Monona......... go right ahead and scare us into thinking about
what we do. Don't let us be complacent and uncaring. Awaken the sleeping!
And Ron and Tony........ keep up the focus on the oxide view of glaze
formulation. It'll get more people buying "Insight" and "Hyperglaze" and
the like and leaning to use them.
I continue to learn from all of you.
I'll stick my nose in now and again too. (OK .....got the flameproof suit
on >)
Best to all,
.................................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
(603) 654-2752
JBaymore@Compuserve.com
76506.3102@Compuserve.com
(16th annual Earth, Water, and Fire summer noborigama woodfiring workshop
in August....email for details)
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