Question: what are the characteristics of good bricks?
Answer: Bricks should be uniform in color, size and shape. ... 
They should be sound and compact.
They should be free from cracks and other flaws such as air bubbles, stone nodules etc. ... 
Bricks should not absorb more than 1⁄5 of their own weight of water when immersed in water for 24 hours (15% to 20% of dry weight).