Bill Aycock on mon 26 may 97
I have followed the "compression", "compaction", "Platelete orientation" ;
"Heat rising" etc thread with pain. I practiced the physical sciences, as
a Rocket Engineer, have been a producing potter, and have managed a small
publication department, in my time. I know something about physics,
something about clay, and something about words. In ALL these aspects, I
was in pain.
The whole question is one of the difference between being technically
correct and being semantically correct. (semantics is the science of
communication and understanding). The question of "Intellectual Freedom"
is interesting, because it WAS displayed, with varying results, by MANY who
participated in the thread. (Think about it!)
1. Heat doesn't care which way is up. It is a form of energy and travels by
conduction, convection, and radiation. However, the action of heat on gases
(covered by the convection part) is to excite them to the point where they
expand, therefore have lower density, therefore are displaced by other,
cooler gases, in a direction away from the pull of gravity. These gasses
rise, and- miraculously, carry the heat with them. Believe me, the heat
energy that influenced the gasses IS going to rise with the gas.
2. Call it what you will, if you take the trouble to "massage" the inside,
bottom of a wheel thrown vessel, AND get as much water out as you can, you
will reduce the probability the you will get "S-cracks". The shape of the
cracks HAS to tell you something! The "S" is caused by the direction the
clay was pulled as the "ball" was opened up. Logic says that the water may
cause the crack, but NOT the shape.
In the commentary on this, the originator of the thread tended to be
purposefully adamant, Vince tended to be right, but in a hurtful way, as
usual, and Karl tended to be flatly dogmatic but very well founded in his
knowledge. It's too bad a discussion couldn't have been entered into,
without the personal attacks.
As a side note- I spent some time looking for some of my S-cracked pieces
(I KNOW I kept some, for use as planters!) and looking in my library for
references to the phenomenon. The surprise was that (using the indexes
only) I found NOT ONE reference to S-cracks, under "S", "cracks",
"compression", or "drying". My library is not small, even though it doesn't
(yet) contain Hamer.
Bill-sitting out a rainy Sunday, on Persimmon Hill.
Bill Aycock --- Persimmon Hill --- Woodville, Alabama, US
--- (in the N.E. corner of the State)
also-- W4BSG -- Grid EM64vr email@example.com