Polished plaster is a term for the finish of some plaster

Plaster

Plaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...

s and for the description of new and updated forms of traditional Italian plaster finishes.

The term covers a whole range of decorative plaster finishes - from the very highly polished Venetian plaster

Venetian plaster

Venetian plaster is a wall and ceiling finish using thin layers of plaster applied with a spatula or trowel which are then burnished to create a smooth surface with the illusion of depth and texture. Venetian plaster techniques include marmorino, scagliola, and sgraffito....

 and Marmorino

Marmorino

Marmorino Veneziano is a plaster or stucco decoration used on walls. It was used as far back as Roman times, but was made popular once more during the Renaissance 500 years ago in Venice....

 to the rugged look of textured polished plasters. Polished plaster itself tends to consist of slaked lime

Calcium hydroxide

Calcium hydroxide, traditionally called slaked lime, is an inorganic compound with the chemical formula Ca2. It is a colourless crystal or white powder and is obtained when calcium oxide is mixed, or "slaked" with water. It has many names including hydrated lime, builders lime, slack lime, cal, or...

, marble dust, and/or marble chips (which give each plaster its distinctive look).

Polished plaster is mainly used internally, on walls and ceilings, to give a finish that looks like polished marble

Marble

Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.Geologists use the term "marble" to refer to metamorphosed limestone; however stonemasons use the term more broadly to encompass unmetamorphosed limestone.Marble is commonly used for...

, travertine

Travertine

Travertine is a form of limestone deposited by mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan, and cream-colored varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot...

, or limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

.

Such plasters are usually applied over a primer

Primer (paint)

A primer is a preparatory coating put on materials before painting. Priming ensures better adhesion of paint to the surface, increases paint durability, and provides additional protection for the material being painted.-When primers are used:...

 and basecoat base, from 1 to 4 layers. They are finished (burnish

Burnish

Burnishing is a form of pottery treatment in which the surface of the pot is polished, using a hard smooth surface such as a wooden or bone spatula, smooth stones, plastic, or even glass bulbs, while it still is in a leathery 'green' state, i.e., before firing. After firing, the surface is...

ed) with a specialised steel trowel

Trowel

A trowel is one of several similar hand tools used for digging, smoothing, or otherwise moving around small amounts of viscous or particulate material.-Hand tools:...

to a smooth glass-like sheen.

Polished plaster is usually sealed with a protective layer of wax.