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Fired Properties
The fired properties include fired shrinkage, water absorption and fired colour.
Fired shrinkage
The shrinkage of the material during the firing stage is important. The extent of these contractions will determine the size of the finished product. If the shrinkage is too large or it is allowed to occur too rapidly, cracking or distortion of the product is likely. The fired shrinkage of the clay provides information on the variations in the composition of the clay.
% dry-fired linear shrinkage( dry basis) is given by
Dry length –Fired length        x   100%
Dry length
Water absorption
The vitrification characteristics of a ceramic material of body may be determined by measuring the water absorption of samples fired at different temperatures. The water absorption is determined using the " boiling technique". The fired specimen was first weighed (Fired Weight). The specimen was then immersed in boiling water for 2 hours after which they are left to soak in cool water. Excess moisture is wiped away from the surface of the specimen and then weighed ( Soaked Weight).

% water absorption is given by

Soaked weight – Fired weight   x   100%
Fired weight
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