Plaster

From MaterialProject.org, the free architectural material catalog

Jump to: navigation, search

Material Catalog · Material by MasterFormat · Help

Material analysis

MasterFormat Number: 092000

Traditional uses

Artistic and structural. A common building material as well as a versatile medium in sculpture.
Plaster has traditionally been used as a finish material for walls and ceilings. Plaster is applied to a substrate such as wood, metal, or gypsum board lath to create a smooth or textured finish.
Plaster is used to cover drywall and create an acoustically controlled finish on walls and ceilings. It can also be used for decorative textures and custom moldings and details.

Emerging uses / trends

Plaster is often used to create decorative textures, moldings, and shapes.
Aesthetic architectural and artistic applications by incorporating color, texture and pattern.
Plaster have been in use in passive fire protection, as fireproofing products.
It is preferred today for the uniformity and wears resistance of its finish, and the creative option it offers. It is also used to match existing finishes in older building

Finish and aesthetic qualities

Plaster is typically available in white, beige, or yellow, however it accepts paint well and can be painted any color. Plaster can also be sanded to create a polished surface and can be easily manipulated with tools.
Plaster can be painted when dry, or mixed with pigments while still wet, as in fresco painting. If painting on dry surface, the plaster may take up to 30-60 days to fully dry.
The surface of a plaster sculpture must be sealed to keep dirt from building up in its pores -- commonly with wax, shellac or linseed oil.
Plaster conforms to the dimensions of the substrate.
In order to bond plaster to a flat surface such as a sheet of plywood, obtain a strong wire-screen material, and staple it to the wood, intentionally leaving gaps between some of the wood and the screen. Your choice of wire-screen -- poultry fencing, hardware-cloth, etc. -- depends largely on the size of the project.
Plaster walls and ceilings present smooth, cool surfaces that can be straight or curved.

Surface forms / shapes

Plaster is sold as a powder in bags, or boxes, as pre-mixed in pails, and can be either slow or fast set. In its powder form plaster must be mixed with water on-site before it is applied and often requires special tradesman for its application.

Cost analysis

20 pounds for about $14

Material properties

Primary structural use

Applied, non-structural finish material applied to a substrate.

Material performance

Fairly soft
Easily manipulated with metal tools or sandpaper.
Once painted or sealed the surface is a lot more durable.
Plaster is a pasty composition of gypsum (or lime or Portland cement) with sand and water.
Plaster makes an excellent base for almost any kind of wall finish: wallpaper, vinyl coverings, cloth, tile, etc. Under tile or any other locations that are expected to be wet, cement plaster should be used.
Unsealed plasters are porous and discolor with airborne grease and dust.

Dimensional and opening restriction

Can be custom poured and sculpted

Acoustic property

Varies depending on binders added and additional ingredients.

Manufacturing process and assembly

Plaster consists of gypsum, lime, portland cement, sand, and water. Binders such as animal hair and fiber may also be added.
Plaster usually refers to plaster of Paris also called gesso-- a mixture of powdered and heat-treated gypsum, which can be mixed with water about 2 parts plaster to each part of water, hardening to a smooth solid which does not shrink or lose volume because it hardens before all the water can evaporate.
Plaster is usually applied in three coats. The first, the scratch coat, is applied directly to the lath and a cross-hatch is etched as it sets. The second coat is called the brown coat and is about 1/2” thick which evens out the surface. The last coat or finish coat may require two people to apply in order to create a smooth surface. Plaster continues to be used on walls and ceilings and it is often used to create intricate moldings and shapes which are cast off-site.
Plaster expands while hardening, and then contracts slightly just before hardening completely. This makes plaster excellent for use in molds, and it is often used as an artistic material for casting.

Environment and Life Safety

Environmental impact

(Sustainability, Off-gassing issues Maintenance/Resilience/Durability:) Lime based plasters have a slightly lower embodied energy than portland-cement based plasters. Lime based plasters do not include petroleum ingredients.
Airborne plaster dust is hazardous to eyes and when inhaled, so proper safety equipment must be worn.
Plaster can be broken up and recycled as hardcore.
The chemical reaction that occurs when plaster is mixed with water is exothermic in nature.
Some variations of plaster that contain powdered silica or asbestos may present health hazards if inhaled.

Flammability rating

Non-Flammable, but varies by wall construction and application.
The finished 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. It also provides some insulation to retard heat flow into structural steel elements that would otherwise lose their strength and collapse in a fire.

References

Notes

Interior Material & Surfaces by Helen Bowers
Construction Material for Interior Design by William Ruff with Arnold Friedmann, Drawings by Philip Farrell.
Material for Interior Environment by Corky Binggeli, ASID

Student contributions

Elisabeth Grace, 2005
Amanda Zani, Spring 2007
Rania Makkas, Spring 2008
Neha Shah, Spring 2009

External links

Additional resources

Material Specific Resources

Shivers, Natalie. Walls and Moldings: how to care for old and historic wood and plaster. New York: Wiley, 1996.

Shivers, Natalie. Walls & Moldings- How to Care for Old & Historic Wood and Plaster. National Trust For Historic Preservation: John Wiley & Sons, 1990.

General Material Resources

Millar, William. Plastering Plain and Decorative. Donhead Pub. Limited, 1998.

Leading manufacturers