The oldest method of improve plasticity is aging or souring. This includes weathering and wintering. After mining the moist clay lumps is stored in the open yard so that it slowly disintegrates under the influence of moisture and temperature changes. The other effect of weathering in open atmosphere is the oxidation of impurities like pyrate into iron sulphate which is washed away in solution by rain.
The effect of weathering can be accelerated by frequent wetting and turning of the clay or by the action of steam.
Fermentation in a clay body containing algae or bacteria can improve the plasticity by creating layers of viscous organic matter surrounding the particles. Unworkable clay can be made into workable by improving its plasticity by weathering process for about 2 or 3 years.
To be contd……
