Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. The most common types of plaster mainly contain either gypsum, lime, or cement, but all work in a similar way.
source/image(PrtSc): OUROBOROS ARQ
The plaster is manufactured as a dry powder and is mixed with water to form a stiff but workable paste immediately before it is applied to the surface. The reaction with water liberates heat through crystallization and the hydrated plaster then hardens.Watch the video from OUROBOROS ARQ where he plasters this amazing miniature concrete house.
Plaster can be relatively easily worked with metal tools or even sandpaper, and can be moulded, either on site or to make pre-formed sections in advance, which are put in place with adhesive.
Plaster is not a strong material; it is suitable for finishing, rather than load-bearing, and when thickly applied for decoration may require a hidden supporting framework, usually in metal.