Fat lime slakes vigorously while hydraulic lime slakes slowly. Fat lime is used to prepare mortar with sand or surkhi while hydraulic lime is used to prepare mortar for thick walls and damp places.

The thickness of steel mould is usually 6 mm. These are used to manufacture bricks on a large scale. They are prepared from steel plates and channels.

In order to develop hydraulicity, it is necessary to have alumina and silica present in chemical combination with limestone. Silicates of magnesium, aluminium and calcium are responsible for hydraulicity.

Bullet-proof glass is made of many layers of plate glass. Alternate layers of vinyl-resin plastic are present in this type of glass. This glass does not allow bullet to pierce through it.

The process of grinding clay with water and making clay plastic is called pugging. Unsoiling is removal of top layer of soil which is full of impurities. In digging, clay is dug out from ground and n spread on levelled ground. In process of wearing, clay is exposed to atmosphere for softening.

Moulding of clay can be done with help of wooden moulds, potter?s wheel or by mechanical means. The method of moulding of clay by potter?s wheel is adopted when shape of tile is circular when on wheel.

Porcelain is prepared from felspar, clay, quartz and minerals and is non-porous, hard and brittle. Low voltage porcelain is obtained by dry process while high voltage porcelain is obtained by wet process.

To prepare soluble glass, quartz sand is melted and n it is grinded and thoroughly mixed with soda ash, potassium carbonate or sodium sulphate. This type of glass is used to prepare acid-resistant cement.

Fat lime is prepared by calcination of a comparatively pure carbonate of lime. It should be composed of about 95% calcium oxide. The percentage of impurities in limestones should not exceed 5% for preparing fat lime.

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.