The following defects in brick occur throughout manufacturing process :-
Defects in size
Defects in shape
Defects in raw materials
In this article, discussion is made on the defects occur in size.
Oversize in all three dimensions
The brick is underfired.
The existence of excessive sand will reduce the amount of dying.
The brick will be lighter as compared to normal standard and if the brick is crashed with another brick, a dull sound will be created rather than a metallic sound.
Oversize in width and length
The brick is squeezed when it is still drench.
It may occur if the brick is laid down on the ground or drying rack once it is molded or when a slop molded brick is pressed to level a deformity.
Oversize in thickness
This problem is mostly found in wire cut bricks.
While wire cutting is progressed, the block of clay is pushed through a row of wire.
The force on the wire may produce movement that modifies the dimension of the opening which the clay moves through.
Undersize in all dimensions
The brick may be built up with an undersized mod, but another reason may be the issue of extreme high of clay content in the batch or if adequate water is used throughout the mixing phase.
Another reason may be over firing, common to bricks around the tunnels in field kiln.