Plaster of Paris (POP) is a quick-setting gypsum plaster (\(CaSO_4 \cdot \frac{1}{2}H_2O\)) that hardens when mixed with water, widely used for decorative interior ceilings, wall finishes, and orthopedic casts. Known for being fire-resistant, lightweight, and durable, it provides a smooth, customizable finish for intricate moldings.