Editing Plaster (section)

===Fire protection===
{{Unreferenced section|date=February 2020}}

[[File:Himeji Castle The Keep Towers.jpg|thumb|''[[Himeji Castle]]'', [[Himeji]], [[Hyogo Prefecture]], [[Japan]]]]

Plasters have been in use in [[passive fire protection]], as [[fireproofing]] products, for many decades.

Gypsum plaster releases water vapor when exposed to flame, acting to slow the spread of the fire, for as much as an hour or two depending on thickness. Plaster also provides some [[thermal insulation|insulation]] to retard [[heat]] flow into [[structural steel]] elements, that would otherwise lose their strength and collapse in a fire. Early versions of protective plasters often contain [[asbestos]] fibres, which since have been outlawed in many industrialized nations.

Recent plasters for fire protection either contain cement or gypsum as binding agents as well as mineral wool or glass fiber to add mechanical strength.
[[Vermiculite]], [[polystyrene]] beads or chemical expansion agents are often added to decrease the density of the finished product and increase thermal insulation.

One differentiates between interior and exterior fireproofing. Interior products are typically less substantial, with lower densities and lower cost. Exterior products have to withstand harsher environmental conditions. A rough surface is typically forgiven inside of buildings as dropped ceilings often hide them. Fireproofing plasters are losing ground to more costly [[intumescent]] and [[endothermic]] products, simply on technical merit. Trade jurisdiction on unionized construction sites in North America remains with the plasterers<!-- ?? -->, regardless of whether the plaster is decorative in nature or is used in passive fire protection. Cementitious and gypsum based plasters tend to be endothermic. Fireproofing plasters are closely related to [[firestop]] mortars. Most firestop mortars can be sprayed and tooled very well, due to the fine detail work that is required of firestopping.