SAH Archipedia uses terms from the Getty Art and Architecture Thesaurus (AAT) to categorize and classify metadata for the entries in the database. For more information on the Getty AAT, click here

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Plastic based on polyether or polyester resin.

polyurethane foam

Versatile plastic foam used as casting, mounting, packing, and transfer material in applications such as upholstery, thermal insulation, garments, material for sculpture, and in objects conservation.

polyvinyl chloride

A thermoplastic resin derived by the polymerization of vinyl chloride, used for thin coatings, insulation, and pipes.

Pompeian red (pigment)

An unstandardized name used for Pozzuoli red, Tuscan red, and dragon's blood.

ponderosa pine (wood)

Wood from the Pinus ponderosa, found in western North America.

poplar (wood)

Soft, lightweight wood of trees belonging to the genus Populus, with color ranging from white to pink or brownish. It has a uniform, straight grain, fine texture, and is easy to work but it is prone to warping. It is primarily used for paneling, light construction, packing crates, joinery, flooring, kitchen utensils, veneer, cardboard, and paper pulp, but historically was used for Italian panel paintings and for sculptures in southern Germany in the late Gothic period.

Populus deltoides (species)

Species of cottonwood poplar native to much of North America; it is known in three subspecies. It is one of the largest North American hardwood trees, growing to nearly 30 meters (100 feet) in height. It has thick glossy leaves and bark that is silver-white and smooth, becoming darker and deeply fissured on older trees. Due to the flat stem of the leaf, the leaf has the tendency to shake from even the slightest breeze. This is one of the identifying characteristics.

Populus fremontii (species)

Species of cottonwood poplar native to southwestern North America.

porcelain (material)

A material comprising white clay, or "kaolin," and a feldspathic rock, that react when fired so the clay serves to hold the shape of the object and the rock fuses into a natural glass. In China, it includes any such ware that is highly fired enough to produce a ringing sound when struck. In Europe, it is limited to hard-fired ceramic that is translucent.

porcelain enamel

A surface created by fusing a thin layer of glass to a metal object in order to prevent corrosion or enhance its beauty.

porcelain tile
No description is available for this term.


A dark purplish-red rock, first quarried in ancient Egypt, containing relatively large crystals in a fine-grained igneous matrix. One of the hardest rocks, it takes a high polish and is valued as a durable sculptor's material and as a decorative architectural material. It is considered the best material for the muller and slab used for grinding artists' colors.


Roofed porchlike spaces, open along at least one side and usually associated with an entrance, supported by columns and often surmounted by a pediment; porticoes may project from the main building mass or be recessed in it.

portland cement

binding material in the form of a finely ground powder, usually gray, that is manufactured by burning and grinding a mixture of limestone and clay or limestone and shale. The cementitious binder for most structural concrete; obtained by pulverizing clinker consisting essentially of hydraulic calcium silicates; contains calcium sulfate as an interground addition. When mixed with water, the anhydrous calcium silicates and other constituents in the portland cement react chemically with the water, combining with it (hydration) and decomposing in it (hydrolysis) and hardening and developing strength. Joseph Aspdin, of England, patented the basic process in 1824, naming it for the resemblance of the cement when set to portland stone, a limestone from the Isle of Portland.

Portland sandstone

Stone of English origin consisting of fossils cemented together with lime.

Portland stone (limestone)

An oolitic limestone widely used for building in England, particularly in London; it is quarried on the Isle of Portland, off the coast of England.

post oak (wood)

Hard, close-grained, durable wood of the species Quercus stellata, native to sandy soils of the central and southern United States. It is tough and rot-resistant, used for fence posts, rough construction, and as a fuel for barbequing meat.

post-tensioned prestressed concrete

Prestressed concrete in which tubes, conduits, or channels are inserted in the concrete where steel reinforcement is needed. After curing, reinforcing steel is inserting into the tubes, stretched to the appropriate tension, and anchored at the ends.

posts (structural elements)

In architecture or other construction, refers to stiff, vertical, relatively isolated members of considerable length. Posts are typically round, square, or rectangular in cross-section and are used in building as supports for a superstructure or to provide a firm point of lateral attachment. They are characteristically relatively undecorated and made of a single timber, but may be made of stone, metal, another material, or composite materials. The term is particularly used for any main vertical support in a timber frame structure. For square uprights in classical style, and for square and rectangular masonry uprights, use "piers (supporting elements)"; for most cylindrical uprights, and for all uprights in steel and concrete frames, use "columns (architectural elements)."

pot-metal glass

Refers to a type of glass characterized by being one deep color throughout its thickness. The process by which it is made is ancient, and requires the combination of silica, potash, and lime, with metal oxides added to the molten glass for color. The name refers to the metal oxides and the custom of melting the compound in a clay pot in the furnace. This type of glass was generally used in making stained-glass windows, with the typical effect of relatively little light penetrating the deep, saturated colors of the glass. A technique was later developed to create "flashed glass," which layers color over clear or white glass and allows more light to pass through the window.

poteaux sur solle construction

Timber frame construction in which the upright posts are raised above damp ground on individual foundation blocks to avoid rotting the frame members and to facilitate replacement of foundation pieces without rebuilding the frame; common in the vernacular architecture of the Lower Mississippi Valley.

Potomac breccia

A striking breccia quarried in the Blue Ridge Mountains in Maryland and Virginia; it consists mostly of limestone, quartz pebbles, and multicolored fragments ranging from sand grains to cobbles, all cemented together in a calcareous matrix. It can be extremely difficult to work as the hard pebbles tend to break away from the softer matrix.

Potsdam sandstone

A siliceous sandstone, from Saint Lawrence County in New York, containing a small amount of iron oxide, giving it its red or reddish-brown color. Although soft enough to work economically when first quarried, it becomes incredibly hard upon exposure, making it an incredibly durable building stone.


Fragments of pottery, especially in archaeological contexts.

potter's pink

A pink pigment used in ceramics and as a pale pink artists color. It was first developed ca. 1790 by a potter in Staffordshire. The color is produced when chromic oxide and tin oxide fuse in the presence of lime. The color is dependent on particle size and is not always uniform. The same pink can also be formed by the combination of chromium and zircon oxides.

precast concrete

Concrete that is cast and cured in other than its final position. For concrete that is deposited in liquid form in the place where it is required to harden as part of a structure, use "cast-in-place concrete."


Substance added to materials, natural science specimens, or foodstuffs to preserve them against deterioration, discoloration, or spoilage. In paint or adhesive, prevervatives are nonvolative chemicals added to prevent fermentation and mold growth.

pressed brick

A stiff mud brick made under high pressure; it is homogeneous, and has increased density and strength.

prestressed concrete

Concrete in which effective internal stresses are induced artificially, usually by means of tensioned steel, prior to loading the structure.

primary wood

Wood derived directly from forest trees, such as lumber, posts, poles, pulp, plywood, particleboard, fiberboard, excelsior, and others, including items such as furniture and woven wood baskets that made directly from tree saplings.

primavera (wood)

Firm, lightweight, fine-textured wood obtained from the species Tabebuia donnell-smithii native to Mexico and Central America. Although the tree is unrelated to true mahogany, the wood resembles it in being easy to work, lustrous, and free of tendency to warp. When first cut, it is pale yellow in color; upon exposure to air and light it darkens to a yellowish rose with streaks of red, orange, and brown. Primavera is used, either in thin lumber or veneer form, for paneling, furniture, veneers, inlaying, and cabinetmaking.

prismatic glass

Glass in which one surface is smooth, while the other is marked by ridges of prismatic section; illuminates very large internal spaces.

private gardens

Originally, gardens designed to reflect the power and largesse of the aristocracy. Contemporary usage extends to gardens maintained by individuals that are somehow enclosed or secluded, regardless of size, and that may evoke the fanciful or fantastic. Variations of the private garden may be designed to house a collection of artworks, or to highlight a particular plant genus.

Pseudotsuga menziesii (species)

Species of North American fir tree having several forms, one with reflexed bracts, that are sometimes considered to be separate species. Trees may reach heights in excess of 90 m (295 feet) and have diameters of more than 4 m (13 feet), but most contemporary stands are composed of trees that are much smaller, due to the fact that many old specimens have been logged. It is noted as one of the best timber trees in North America, as well as a popular ornamental and Christmas tree, and is used for reforestation along the Pacific Coast.

pudding stone

Conglomerate rock containing numerous rounded pebbles.


Wood suitable for making paper pulp.

pumice (volcanic rock)

A pale gray, porous variety of the volcanic stone rhyolite; it is composed of potassium aluminum silicate with small amounts of iron and alkalis. Pumice is used as an abrasive for polishing jewelry, cleaning metals, and smoothing vellum and parchment. In its solid form it is used as an abrasive and aggregate and in its powdered form it is used as a polish and abrasive.

punk (wood)

Wood rendered dry, crumbly, and easily ignitable by the action of certain fungi; often used as tinder.

purple slate

Slate that has components of hematite and chlorite, causing a purplish color.

Pyrex (TM)

A low-expansion type of bora-silicate glass.

quahog shells
No description is available for this term.

quarry tile

Unglazed ceramic tile, machine-made by the extrusion process from natural clay or shales.

quarter-sawed lumber

Lumber that has been sawed so that the wide surfaces extend approximately at right angles to the annual growth rings. Lumber is considered edge grained when the rings form an angle of 45 degrees to 90 degrees with the wide surface of the piece.

quartz (mineral)

The most common variety of silica; commonly occurs as crystals.

quartz crystal

A transparent variety of the silica mineral quartz that is valued for its clarity and total lack of color or flaws. Vessels and spheres have been carved from large crystals since ancient times, and the application of the word "crystal" to fine glassware derives from this practice. Quartz crystal formerly was used extensively as a gemstone, usually brilliant-cut, although it has now been largely replaced by glass; rhinestones originally were quartz pebbles found in the Rhine River. The optical properties of quartz crystal led to its use in lenses and prisms; its piezoelectric properties are used to control the oscillation of electrical circuits. Its physical properties are those of quartz.

quartz porphyry

A porphyritic rhyolite containing phenocrysts of quartz and alkali feldspar in a microcrystalline or cryptocrystalline groundmass.


A metamorphic rock composed largely of granular quartz which is cemented by silica forming a homogeneous mass of very high tensile and crushing strengths; especially used as a building stone, as gravel in road construction, and as aggregate in concrete.

queen's metal

A britannia metal with a small amount of zinc.

Quercus (genus)

Genus containing around 450 species of ornamental and timber trees and shrubs, found chiefly in north temperate regions and at high altitudes in the tropics. The durable wood has a distinctive coarse grain. The thick bark from some species is used for its buoyancy. Tannins and dyes can be extracted from the bark. Oak emits organic acids as it ages. Many plants commonly called "oak" are not Quercus, including African oak, Australian oak, bull oak, etc.

Quercus agrifolia (species)

Species of oak native to the Pacific coastal regions of North America from California to the Baja peninsula; most often shrubby, but may reach heights of 20 m. Distinguished by holly-like leaves; may live to 250 years in age. The hard wood has been used for shipbuilding in the past, but now the tree is primarily used as an ornamental and for shade.

Quercus alba (species)

Species of oak native to the eastern United States, reaching 45 m (50 feet) in height, having pale-gray, shallowly fissured, scaly bark, and glossy, bright green leaves that narrow toward the base and turn wine red in autumn. Specimens are known to have lived for up to 600 years. It is an important timber tree, having light brown, coarse-grained, strong wood, used for millwork and flooring.

Quercus laevis (species)

Species of small, slow-growing deciduous shrubby tree native to the dry, sandy areas of the southeastern United States, on the coastal plain from Delaware to Florida and Louisiana. It reaches 10 meters in height, has deeply incised leaves with 3-7 slender lobes, and acorns that take 18 months to mature. It hybridizes easily with southern red oak (Q. falcata), bluejack oak (Q. incana), laurel oak (Q. laurifolia), and water oak (Q. nigra). Its name "turkey oak" is derived either from the turkey-footprint shape of its leaves or from the fact that wild turkeys eat the acorns.

Quercus virginiana (species)

Species of evergreen tree native to the southeastern and gulf area of the United States into Mexico, and Cuba, having a coarse, reddish brown bark and reaching 50 feet in height. Valued for its hard, durable wood, formerly used in shipbuilding; today most often used for shade trees. It is readily hybridized, and thus confusion regarding varieties and certain common names has arisen.


Stones used to form the corner of a wall of masonry, especially when accentuated by a difference in the surface treatment from that of the rest of the wall mass.

racks (supporting devices)

Frameworks of wire, pegs, bars, gratings, or shelves in or on which articles are placed or suspended, often for storage or stowage; may be freestanding or attached to surfaces.

railroad ties

Strong internal rectangular supports for the rails in railroad tracks.

rails (transit system elements)

Rolled steel bars, commonly T-sections, designed to be laid end to end, usually in pairs and in parallel lines, to provide the running surface for certain transit vehicles.

rammed earth

A material usually consisting of clay, sand, or other aggregate, such as sea shell, and water, which has been compressed and dried; used in building construction.

random ashlar

Building material comprising roughly squared stone blocks of different sizes laid in courses. The horizontal and vertical joints do not line up consistently and smaller stones may be used to fill in gaps.


Synthetic fiber made from regenerated cellulose.

No description is available for this term.

red beech (wood)

Wood of the species Nothofagus fusca, native to cooler regions of the southern hemisphere. It is used in the making of flooring, toys, and tool handles.

red cedar (wood)

General term referring to wood of many evergreen trees of the cypress family.

red fir (wood)

General term for wood from any of many species coniferous trees, including the Scots pine, Fraser fir, Douglas fir, red fir (silvertip fir), and silver fir.

red granite

Granite with a mineral composition that results in a red color and usually a relatively coarse texture.

red gum (wood)

Wood of the species Corymbia calophylla, native to Australia. It is yellowish-red in color, and is used in the manufacture of flooring, paving, and stair treads.

red marble

Marble with a mineral composition resulting in a predominantly red color.

red oak (wood)

In the lumber trade, a general term for wood of many species of oak, including Q. rubra, belonging to a subgroup of oak trees native to North and South America, characterized by having bristle-tipped leaves, acorns with hairy shell linings, and bitter seeds that mature in two seasons. Red oak wood is typically hard, coarse-grained and used commercially for flooring, furniture, cabinets, paneling, and millwork.

red ocher (pigment)

Earth color made from clay or by calcining selected grades of yellow ocher. This type is sometimes called burnt ocher.

red pigment

Pigment having the color red, which is produced by light having a spectrum dominated by energy with a wavelength of about 630–700nm.

red pine (wood, general)

Wood from any of various trees, usually pines or other conifers having reddish bark or wood.

red slate

Slate that has a component of hematite, causing a reddish color.

redwood (wood)

Wood from any of several species of cypress, pine, or cedar having reddish wood.

reflecting pools

Designates artificial areas of water, usually of geometric shape, specifically designed and located so as to mirror buildings or other structures.

reflective glass

Window glass coated on the outside with a transparent metallic coating that reflects light and radiant heat.

reinforced concrete

Concrete that contains embedded reinforcements, typically steel bars, in order to increase strength.

reinforcing bars

Steel bars, usually with manufactured deformations or threading, used in concrete and masonry construction to provide additional strength.

resin (organic material)

General term for solid or semisolid organic substance usually obtained from plant secretions, but sometimes obtained from insects or synthetically produced. It is soluble in organic solvent but not in water, and is commonly used in varnish, printing ink, and size. It is distinguished from "gum" by not being dissoluble in water. To distinguish between natural and synthetic resins, use the narrower terms "natural resin" or "synthetic resin."


Any of a number of extrusive acid igneous rocks, usually porphyritic and exhibiting flow lines, with phenocrysts of quartz and alkali feldspar in a glassy to cryptocrystalline groundmass; the extrusive equivalent of granite.


Layers, facings, or protective embankments comprised of large irregular and randomly placed stones to prevent erosion, scour, or sloughing; also the stone so used.


The land margins of rivers.

riverine bodies of water

Bodies of flowing water moving in one direction, including streams and rivers.


18th-century term for ornamental trimming in the form of bands or stripes on a robe or gown.

rock (inorganic material)

Naturally formed aggregate of one or more minerals. For processed or dressed rock use "stone."

No description is available for this term.

Roman brick

Brick whose nominal dimensions are 2 2/3 x 4 x 12 inches.

Roman tile

A channel-shaped, tapered, single lap, roofing tile.

Romanesque Revival

Refers to the style in European and American architecture dating from the 1820s to the end of the 19th century. Based on the style of the 11th- and 12th-century Romanesque church architecture, it is characterized by semicircular arches, groin and barrel vaults, and the spare use of naturalistic ornament.


Any material used as a roof covering (such as shingles, slate, sheet metal, or tile) to make it wind- and waterproof, and often to provide thermal insulation.

roofing slate

A thin, usually rectangular, piece of certain varieties of slate or other stones which split readily into sheets and are used to cover the roofs of buildings.

roofing tile

Type of tile for roofing, usually of fired clay, concrete, or asbestos cement; available in many configurations and types such as plain tiles, single-lap tiles, and interlocking tiles.


Heavy cord, at least 1/4 inch in diameter, formed by twisting or braiding three to six yarns of natural or artificial fiber. In ancient Egypt, rope was made from reeds or date palm fibers. Ancient rope was also made from flax, grass, esparto grass, hemp, sisal, coir, cotton, jute, papyrus, and camel hair. Up to 1850, most rope was made from hemp or sisal. After this point, abaca and agave became the fibers of choice. By the 1950s, synthetic fibers (nylon, rayon, saran, polyester, etc.) became predominant. Glass and metallic fibers have also been incorporated into rope for added strength and resistance to fire and chemicals.

Rosa Porriiño granite
No description is available for this term.

rose quartz

A pink variety of quartz used as a gemstone.

rosewood (wood)

Wood from several tropical trees of the genus Dalbergia, all having a dark red or purplish color streaked and variegated with black. Rosewood timber produces a rose-like smell when cut. The wood has a fine grain, smooth texture, and polishes to a high gloss, but because of its resinous nature is difficult to work. It is used for cabinets, musical instruments, piano cases, and veneer. It was popular during the late 18th and early 19th centuries. It is still used to fashion xylophone bars, but waning supplies restrict its use. Only around 15 of the species in the large genus Dalbergia yield rosewood.


The solid, brittle, clear resinous residue left after the distillation of turpentine from balsam, having a color ranging from yellow or reddish-brown. It becomes sticky when warm and has a faint pine-like odor. Primarily composed of abietic acid (about 80%), rosin reacts in hot alkaline solutions to form rosin soaps. Rosin weathers poorly, becoming oxidized and brittle with age. It also has poor moisture resistance. Although many of its aging properties are undesirable, rosin is or was used as an ingredient in paints, varnishes, inks, adhesives, sealing wax, soldering fluxes, sizing paper, and linoleum. Because it increases sliding friction, it is commonly used for coating bows of some stringed instruments, and as a slip preventative on the floors of stages and shoes of dancers. The inexpensive resin is also used for sizing paper.


Plaster made of lime mixed with shells or pebbles and used for covering buildings usually by being thrown from a trowel forcibly against a wall.

round barns

Historic barn design that flourished between the late 19th and early 20th centuries in the United States and Canada. Round barns were built in a variety of shapes: octagonal, polygonal, or circular.


Rough, broken stones or bricks. For use in masonry, use "rubblework."

rubble concrete

Form of concrete reinforced by broken stones or brick.