If moist clay articles are dried by passing in between porous clays, it dries very fast. However the strength will be reduced. When dried clay wares are exposed to the air, moisture is taken up again and they become mechanically weaker.
The shrinkage associated with drying is not uniformly distributed over the article. It would be the same everywhere with the evaporation of water was equal from all surfaces, but evaporation is most rapid from those which are swept by the air used for drying.
The method of shaping greatly influences drying shrinkage. In clay from an extrusion press the shrinkage is greater, parallel to the direction of extrusion than at right angle to it. For scientific purposes it is preferable to deal with volume changes rather than changes in linear dimensions when considering shrinkage.
To be contd…………..
