Characteristics of good bricks :
1. Appearance and colour : A good brick should have a uniform rectangular shape with even surfaces and sharp corners. It should be free from cracks. It should have a uniform brick-red colour.
2. Structure : If the brick is broken into two, the broken surface should be compact and free from cracks.
3. Hardness and soundness : Good bricks should be hard and should not be scratched by fingernail. Also, should give a metallic sound when two brick are struck to each other.
4. Strength : A good brick is strong enough to not to break, when dropped on another brick from a height of about 1.25 Meters.
5. Compressive strength : A good brick should have a minimum of 35 kg/Sqcm. compressive strength.
6. Absorption of water : A good brick when immersed in water at ambient temperature for 24 hours should not absorb more than 20% of water by weight.
7. Efflorescence : It should not contain alkalis or any hygroscopic matter, which cause efflorescence resulting in brick decay.
8. Durability : A good brick should be able to withstand weathering actions of Sun, rain wind etc.
9. Fire resistance : A good brick should be able to withstand a
temperature up to 1500˚ F or 816˚ C.