iandol on fri 2 may 03
If you read Lawrence and West carefully you will realise that in spite =
of giving pictures which show aligned pen strokes in the diagram =
representing clay which is being slapped about onto a surface or cut and =
re-assembled in the wedging process that they tell you water in plastic =
clay becomes a solid substance. Read page 80. For this to make sense a =
reader has to understand the meaning of "Adsorbed Water" and "..the non =
liquid nature of the initially adsorbed water..". Earlier, p 55, "..The =
incorporation of such an ion (cf Ca2+) in this position would greatly =
strengthen the structure and enhance its build up and extension to large =
distances from the surface of the crystal..."
Now for a quote you will not have read, from Dr. Wayne E. Brownell, =
Professor of Ceramic Science, New Your State College of Ceramics at =
Alfred University, written in 1976.
"....The action of the ions to structure the water is caused by the =
attraction of the appropriate points of the tetrahedral molecules to the =
electrically charged ion: a long range structure is built up by dipole =
attraction of one water molecule after another which results in an "ice =
like" structure surrounding each ion. If enough ions are present, the =
whole bulk of the water is affected..."
He also points out that when the concentration of clay is high enough in =
water the mixture does not exhibit a freezing point. I have found that =
when clay freezes a proportion of water changes to Ice but the remainder =
does not separate and the clay/water combination has a brittle fracture =
surface when broken suggesting only one phase is present in the =
material. The obvious interpretation of this is that all but a small =
proportion of the water in plastic clay is behaving as Ice, that it will =
have all of the properties of Ice.
If you were willing to do the research i'm sure you would find this =
information in the library at Alfred.
I need prove nothing. You continue to believe and teach what you have =
learned. Pots we make will be unforgiving of our ignorance.....
Ivor Lewis. Redhill, South Australia