Joseph Herbert on sat 27 oct 01
Paul,
At the very least it is clear that the Unity Formula is a useful analytical
tool. I believe that its current usefulness is limited by the precision
(lack of) of analysis of the feedstocks that go into our recipes rather than
by an error in the underlying assumption of a "Glaze Molecule". It is not
unusual to use not-entirely-accurate models of things for analysis when
solving scientific problems. One of the most frequently seen examples is
the use of Newtonian equations of motion when relativistic equations are
more accurate. In the chemical world, the idea of "shells" an echo of the
Bohr planetary theory of the atom, is used many times even though quantum
mechanical probability clouds are (apparently?!) a more accurate
representation of the true structure of an atoms electrons. The word
"orbital" is used routinely even though the idea it was once intended to
convey has been largely superceded.
I have not seriously studied the history of ceramic science but the work of
Seger must have been a revelation in an industry that had relied on trial
and error development of trade secrets with little (no) idea of what was
going on. The effort to apply scientific observation to the development of
ceramic glazes must have been revolutionary. The revolution probably took
some time. Indeed, since we are having this discussion, it must still be
going on.
I suppose the greatest thing we gained from that research were pyrometric
cones. Before that I suppose draw rings were used but I wonder about the
process in the coal fired bottle kilns where all the ware was inside
saggars. There must have been some disconnect between any sample you could
draw, that was exposed to the acrid coal fumes, and the protected ware in
the closed saggars. Anyway, these little things we take for granted must
have been a great aid to increasing the consistency of firing in industrial
kilns.
The other thing gained was some freedom from the vagaries of materials
compositions. If a material becomes unavailable, the unity formula provides
a guide to recovering the glaze with other materials. It has become clear
in our non-industrial cases that the main oxide divisions of the formula do
not tell the whole story. Indeed, it seems clear in many cases that the
contribution of unrecognized trace elements must be very important. The
adage about glaze recipes not traveling well points to this possibility. It
is certainly true that the calculated recipe using other materials will
almost certainly not produce the same appearance as the recipe with the
original ingredients. BUT, we are guaranteed that the new recipe is
chemically similar to the desired glaze which make it a much better place to
start testing than is any alternative.
Whatever the flaws of the unity formula are, it offers us insight (no plug
intended here but this is probably why the name was chosen) into the
activities and contributions of all these different ingredients that we
send into the fire hoping for pretties in return.
Joseph Herbert
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