Define Plaster of Paris?

Plaster of Paris (POP) is a quick-setting material made by heating gypsum to about 150°C, used in construction, art, and medicine. Plaster of Paris is one of the most commonly used building and sculpting materials. It is lightweight, easy to mold, and quick to harden. POP is widely used in making decorative designs, false ceilings, and even in medical casts for broken bones.

Chemical Composition

Plaster of Paris is chemically known as calcium sulfate hemihydrate (CaSO₄ · ½H₂O). It is produced by heating gypsum (CaSO₄ · 2H₂O) at about 150°C. The reaction is:

CaSO₄ · 2H₂O → CaSO₄ · ½H₂O + 1½H₂O

Properties of Plaster of Paris

• Quick Setting: Sets within 5–10 minutes when mixed with water.
• Lightweight: Easy to transport and use.
• Porous: Allows it to absorb moisture, which can be both useful and limiting.
• Smooth Finish: Gives a shiny, smooth surface when applied.

Uses of Plaster of Paris

• Construction: Used in making decorative ceilings, wall coatings, and designs.
• Art and Sculptures: Used by artists to make models and statues.
• Medical Use: Used in making orthopedic casts for fractured bones.
• Fireproofing: Acts as a protective coating for buildings.

Advantages and Disadvantages