Plaster is a mixture of Portland cement, sand, and water that is applied in a thick, mud-like consistency to a base of wood or metal lath or perforated plasterboard. It is usually applied to lath, foundation of a plaster wall i.e.., thin sheets of wood, sheets of expanded metal, or specially prepared gypsum boards, but it may also be applied to any masonry surface rough enough to hold it. For interior work, two coats are generally applied- a rough sandy undercoat and a smooth white finish coat which can be left as it is or painted, papered or covered with canvas or other fabric as embellishment and protection.
Plaster has been used for ages because it is not costly, can be applied without visible joints to surfaces of almost any shape, smoothly hides anything behind it. And it is an excellent background for varied surface treatments. Its disadvantages are it does crack and often chips.
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