Plaster

Plaster is a versatile building material used to cover walls and ceilings, as well as to create decorative shapes and designs. While “plaster” usually refers to indoor uses, “render” is the term for outdoor applications, and “stucco” describes plaster that is shaped to make raised, artistic patterns instead of flat surfaces.

Most common plasters are made from gypsum, lime, or cement. They start as a dry powder mixed with water to become a thick paste that hardens quickly. This makes plaster easy to shape with simple tools like metal spatulas or sandpaper, and it can also be molded into shapes either before or during application.

Besides building decoration, plaster has many other important uses. In medicine, plaster orthopedic casts support broken bones while they heal. In dentistry, plaster helps create models from dental impressions. Artists have long used lime plaster for fresco paintings, where colors become part of the hardened plaster itself. In ancient times, plaster was also used to make large decorative sculptures for walls, though many of these wonderful works have not survived to today.

History

Plaster has been used as a building material and for decoration for over 5,000 years, starting in the Middle East. In Egypt, people burned gypsum, crushed it into powder, and mixed it with water to make plaster. They used this plaster as a mortar between pyramid blocks and to create smooth wall surfaces. The Romans later spread plaster-working techniques to Europe.

Types

Plaster is a material used to cover walls and ceilings, making them smooth or adding decorative designs. There are several types of plaster, each with its own uses and properties.

Clay plaster is made from clay, sand, and water, sometimes with plant fibers added for extra strength. It has been used for thousands of years, including by settlers in early America. Clay plaster was often mixed with materials like straw or manure to help it stay strong.

Gypsum plaster, also called plaster of Paris, is made from a powder called calcium sulfate hemihydrate. When mixed with water, it hardens quickly and is used for making statues, toys, and even medical casts for broken bones. It is also used to make smooth walls and decorative designs on ceilings.

Lime plaster is made from calcium hydroxide and sand. It hardens when it reacts with carbon dioxide in the air. Lime plaster was commonly used in old buildings and is still used today for painting fresh, wet plaster with colorful designs.

Cement plaster is a mix of plaster, sand, Portland cement, and water. It is used to create smooth surfaces on walls, both inside and outside buildings. It is strong and lasts a long time.

Heat-resistant plaster is used when regular plaster would melt or fall off due to high temperatures, such as on walls near chimneys or in places that need to be fireproof. It is made from special mixtures that can handle heat better than regular plaster.

Applications

In decorative architecture

Plaster is a versatile material used to add beautiful details to the inside of buildings. It can create patterns that look like wood or stone, or designs inspired by nature such as leaves and flowers. Today, plaster is also used to make false ceilings, where thin sheets of plaster are attached to the ceiling and decorated with lights and colors.

Art

See also: Plaster cast

Plaster is often used in art because it is easier to shape than stone or wood. Artists use plaster to make detailed wall decorations and sculptures. It is also used to create molds for making terra cotta or concrete pieces. Plaster is great for casting because it expands and contracts slightly as it hardens, which helps make accurate molds.

Medicine

Plaster is important in medicine, especially for supporting broken bones. When mixed with water, plaster bandages harden around a broken limb to keep it still while it heals. Plaster is also used in dentistry to make models of teeth and gums, helping dentists create accurate dentures.

Fire protection

Plaster has been used for many years to help protect buildings from fire. When heated, gypsum plaster releases water vapor, which slows the spread of fire. It also insulates and protects structural steel from heat. Modern fireproofing plasters may contain materials like mineral wool or glass fiber to improve their performance.

3D printing

Plaster is used in some 3D printing techniques. In powder bed and inkjet head 3D printing, water reacts with gypsum plaster to create the desired object layer by layer.

Gallery

• Plasterwork in Pompeii (79 AD)
• Figure of a woman; 5th century; painted plaster; height: 38.4 cm (15.1 in), width: 14.7 cm (5.8 in), depth: 9.6 cm (3.8 in); Metropolitan Museum of Art
• Seated Voltaire; by Jean-Antoine Houdon; 1778; plaster, tinted to imitate terracotta; overall: 35.6 cm × 14.6 cm × 20 cm (14.0 in × 5.7 in × 7.9 in); Metropolitan Museum of Art
• Young girl; first modeled: 1779–1780; plaster; height: 36.8 cm (14+1⁄2 in); Metropolitan Museum of Art
• Nymph; 1805–1810; plaster; height: 155.6 cm (5 ft); Metropolitan Museum of Art
• Photo of a plaster model of an ornamental oeil-de-boeuf for the new Louvre; circa 1856; Metropolitan Museum of Art
• Jupiter and the Sphinx; 1868; tinted plaster; 116.8 cm × 112.1 cm × 60.3 cm (3 ft 10 in × 3 ft 8+1⁄4 in × 1 ft 11+3⁄4 in); Metropolitan Museum of Art
• The Young Mother; by Bessie Potter Vonnoh; circa 1896; plaster; Portland Museum of Art (Portland, US)

Safety issues

When plaster mixes with water, it can become very hot, and in large amounts, it may burn the skin. People working with plaster that contains certain materials like silica or asbestos should be careful not to breathe in the dust, as this can harm their health over time.

Special rules exist to keep workers safe when handling plaster. Limits have been set on how much plaster dust can be in the air during work to protect people’s breathing and overall health.