In forming process where there is no great application of pressure a trail shaping on the wheel or rolling out with a hand roller at different water contents in the body can be used to find out the workability. A widely used apparatus in laboratory is the Pfefferkorn apparatus in which a cylinder of plastic clay of a given height is forced to compress by a blow from a falling weight and the deformation developed and absorbed is plotted against water content. The plasticity determination by this method is most conveniently carried out in the following way. The water content required to give the most plastic body is determined subjectively by kneading the clay with water and using the thumb and index finger as the guide. The deformation height of sample is then determined and taken as measure of plasticity.
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