Gypsum is a mineral building material based on calcium sulphate. From natural gypsum rock or from industrial by-products, calcined gypsum (hemihydrate) is produced by heating. Mix this powder with water and it sets quickly into a hard, stone-like mass. Gypsum is thus one of the most important materials in interior finishing.
Application
Gypsum is used for plastering walls and ceilings, for casting mouldings and ornaments, and as a raw material for plasterboard, gypsum blocks and anhydrite screeds. As a repair material for filling holes and chases it is also popular, because it hardens quickly and is easy to work.
An important advantage is that gypsum acts as a moisture regulator: it can absorb water vapour from the air and release it again later, contributing to a pleasant indoor climate.
Characteristics
Gypsum sets quickly and expands hardly at all, so cracking is limited. The material is light, fire-resistant and easy to work. A drawback is its limited moisture resistance: ordinary gypsum is not suitable for permanently wet rooms or outdoor use unless specially treated. The setting time can be controlled with retarders or accelerators.
Related terms
- plasterboard
- plaster layer
- plastering
- anhydrite screed
- lime
- binder
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