Gypsum panels are a construction material, consisting of large, flat sheets of gypsum plaster sandwiched between two layers of paper. Gypsum panels are also known as drywall, wallboard, gypsum board, or Sheetrock®. They are used for covering interior walls and ceilings, and have gained popularity for being faster, cheaper, and easier to use than traditional alternatives.
A mineral with the chemical composition CaSO4·2H2O, gypsum comes from one of two sources. Natural gypsum is obtained by crushing mined gypsum crystals. Synthetic gypsum is created as a byproduct of coal- or oil-burning power plants, through a process called flue-gas desulfurization (FGD). Both synthetic and natural gypsum are chemically bonded to water that must be removed before it can be used. This is accomplished through a calcining process in which the gypsum is heated to about 350° Fahrenheit (176.7 Celsius).
The calcined gypsum is mixed with water, paper or fiberglass fibers, and various chemical additives to create a plaster. The wet plaster is fed between two rolls of paper to make sheets. The sheets are then dried in a kiln and cut into panels. Upon drying, the gypsum plaster hardens and bonds to the paper sheets, creating a solid, durable construction material.
Gypsum panels were developed in order to reduce the amount of time required to finish interior walls in a home. Before their invention, walls were finished by applying multiple layers of wet plaster, a messy and time-consuming process. The first gypsum panels were created late in the 19th century by Augustine Sackett. These used sheets of felted wool rather than wood pulp paper, and were usually used as an underlay for plaster rather than as a wall finishing. By 1930, gypsum panels had more or less reached their modern form, though refinements in the materials and manufacturing process would continue through the 20th century.
In addition to ease of application, gypsum panels provide additional benefits. Gypsum is naturally fire-resistant, and the panels are usually treated with additional fire retardants. When heated by fire, water trapped in the plaster boils off, lowering the temperature in adjacent rooms. The panels are also usually treated to resist mold and mildew.
The Gypsum Association, an industry trade group, points to numerous environmental benefits of using gypsum panels. They claim that nearly 100% of the paper used in manufacturing is recycled. The FGD process, by which synthetic gypsum is created from fossil fuel emissions, keeps sulfur out of the air, and using it as a building material keeps it from becoming solid waste. In the early first decade of this century, the use of synthetic gypsum increased dramatically, and it now accounts for nearly a third of the gypsum used.