Vidreiro on sun 2 may 99
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=A1BaO again?=21 What topic on has been more tortured than this?
=3E ...Copper, for example, is quite different. There are a very few people=
who
have
=3EWilson's disease and find copper extremely toxic=3B however little is =
known about
the chronic effects of copper
=3Eon the general population.
Nonsense.Hooey. Horse Puckey. Balderdash. Bobagem. How else can it be put? =
How
many tens or hundreds
of =2Amillions=2A of US homes, offices, factories... employ(ed) Cu plumbing?=
You
don't have to use Bose-Einstein
statistics to recognize that systemic disease caused by heavy exposure to
omnipresent Cu (ions) in our
plumbing would have become abundantly obvious a long time ago. To suggest, =
as
has been done here that Ba
bearing blue glazes as a lot have the insidious character of Hepatitis-C, =
and
should therefore be subject to an
auto-da-fe toward the altar of granola fascism is nothing short of, well, =
wierd.
This is an issue that has been hyped and huffed with more evangelistic zeal =
than
even the ever
breathless Tony Alamo can muster. Ba is a primary ingredient in many glazes =
used
for extremely hostile
environments -- chemical vats, for example. It can and has been used in
tableware glazes for eons showing
utterly no ill effect toward the stability of the decoration and/or its =
owners.
Probably the most damage that's
ever been done by sending out a less than stable Ba/Cu blue (or any other
host/color combination, for that
matter) is that incurred to one's credibility as a competent professional.
Imagine Ben Stein's voice on the
phone: =22yooou took MY money for a dissolving pot=22.
At the core of this debate, and I've never heard it said, is that you can =
use
almost anything in the Periodic
Table in a =22glaze=22, but to obtain specifically desirable results or do =
more than
blither about the dustbins
looking for something =22else=22, and maybe making dissolving glaze, it =
takes an
elemental and intimate familarity
with the substances involved. God, I wish it were different, too.
This isn't to say that using implausible combinations of materials hasn't =
now
and again produced remarkable
effects, however (and here he goes with a Platitude), fooling with glaze =
absent
a bit of chemistry is like
trying to write poetry absent a bit of grammar. None of this is to deny =
potters
who prefer or are obliged to
use rustic methods and vast intuition. Hey, I, more than anyone, am =
completely
awed by Olarias in Brasil. It's
just that for most anyone reading this it's so easy to obtain pretty well
defined raw materials -- except, I
find, for the rare earths, but that's another post -- he said PO'd over this
batch of Pr green -- which, by the
way , flouresces orange...very cool effect.
The stability of any substance in a glaze is not a matter of winsome =
ambition,
but of careful combination of
its' mates. How this all goes is laid out in any number of the boilerplate
references, like
Parmelee/Harman/Greene, and some of the Studio lexicon. The literature on =
the
durability of glazes is actually
quite vast and where limits lie is pretty well understood for wide ranges of
compositions. That's all to say
that you can do it if you want to bother to go out and learn how. Not =
wanting to
learn how invites Sisyphisian
tasks like having to stir your goopy settled glaze all the damn time ....or
worse, having it dissolve before
someone who paid money for it.
Now having positioned himself as the Milosevic of glazeovo, Karl says: =
PbO-2SiO2
is an excellent thing to put
in a wide variety of glazes as a starting flux. As commercially prepared, it=
is
virtually insoluble --
certainly in anything to which it is to be exposed, like water in glaze =
slip.
For strong decorative effect --
deep color, high index glaze, PbO is essential and it is woefully underused =
in
many non-tableware applications.
It makes a palette which is unique (ie Pb-Cr crystalline Oranges), and PbO =
much
more so than BaO represents,
I'll argue, a legitimate and widely misapprehended region of ceramic =
decoration.
Try making Au ruby without it.
PbO, BaO, CuO and their kind are highly useful and completely safe things to=
use
on tableware. In fact, here in
the US the incidences of Pb poisoning glaze and glassware:
A. Were have been and are Extremely rare, and
B. Most (all?) instances of Pb poisoning in this now gone century in the US
involved imported wares -- often
really rude stuff, sometimes simply smeared with litharge for glaze. =
=2AMany=2A
places still use this sort of ware
for daily use, but certainly not here, and
C. The technologies for developing =2Ahighly=2A stable PbO, BaO, CuO bearing=
glazes
are very, very mature. An
afternoon in any decent university library should net you reams of =
literature on
the topic.
To can this up for the moment.... it's Saturday and the pretty lesbian has
agreed to have dinner again --
tonight I think we'll do Thai. So to close, it's well to recall that =
excluding
those who operate(d) sloppy
studios/factories or fools who smoke, drink, eat, pick their.... in the
batchroom and/or who did any number of
assorted other dumb things, like lick brushes, instances of studio =
poisonings
are statistically =A4microscopic=A4.
Less than triflingly small, like, pico scale. Dead Friskys and Spots, =
likewise.
Throughout the 50's-60's hobby
ceramics movement (can we call it that?) PbO glazes were common and let's =
note
that instances of Love Canal in
granny's basement or granny suddenly tottering about drooling uncontrollably
because of her potting are
virtually unheard of -- hell, the copper pipe didn't get her, either. Now
what.... Ah=21 Manganese=21 That's it=21
KpP
--
=22It's not what we don't know that hurts, it's what we know that isn't so.
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