Explanation: There are two types of bricks prepared by hand moulding. These are ground-moulded bricks and table-moulded bricks. Moulding can also be done by machines. These machines are mainly divided into two categories – dry clay machines and plastic clay machines.

Explanation: A frog is used to indicate the trade name of the manufacturer. It is a mark of depth about 10-20 mm. It is placed on raw bricks during moulding and serves as a key for holding mortar.

Explanation: Continous kilns are continuous in operation which means that in these kilns, loading, firing, cooling and unloading, all are carried out simultaneously. The various types of continuous kilns are bull’s trench kiln, Hoffman’s kiln and tunnel kiln.

Explanation: Hoffman’s kiln is also known as a flame kiln. It is constructed overground. Bricks of good quality are produced in this kiln since they are burnt equally and evenly.

Explanation: The shape of Hoffman’s kiln is circular in plan. It is divided into a number of chambers and each chamber is provided with the main door for loading and unloading of the bricks.

Explanation: A good brick should be well burnt in kilns and should have a low thermal conductivity. It should give a clear ringing sound when struck with another brick. It should be uniform in shape and should be sufficiently hard.

Explanation: Second class bricks should not absorb water more than 22% by weight when soaked in cold water for one day. Also, first-class bricks should not absorb water more than 20% by weight.

Explanation: The minimum crushing strength of a brick is generally 35 kg/cm2. It is found out by placing the brick in a compression testing machine and it is then pressed till it breaks.

Explanation: Presence of soluble salts causes efflorescence on the surface of the bricks. The efflorescence on the surface of bricks is said to be slight if the white deposits cover about 10% of the surface. It becomes heavy if these deposits are found on more than 50% of the surface.

Explanation: First class bricks are table-moulded while second class bricks are ground-moulded. The surface and edges of first-class bricks are sharp and straight while the surface of second class bricks is somewhat rough.

Explanation: A cownose brick is moulded with a double bullnose on the end. A bullnose brick is moulded with a rounded angle and is used for a rounded quoin.

Explanation: Pressed and wire cut bricks are much heavier than the ordinary hand-moulded bricks. These bricks have sharp edges and corners. They exhibit uniform texture and their external surface is smooth.