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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paint (coating)

Any dispersion of pigment in a liquid binder. Paint is applied with a brush, roller, sprayer, or by dipping and dries to form a decorative or protective film.

paintings (visual works)

Unique works in which images are formed primarily by the direct application of pigments suspended in oil, water, egg yolk, molten wax, or other liquid, arranged in masses of color, onto a generally two-dimensional surface.

palisades (outworks)

Barriers composed of long stakes, usually with pointed tops, driven into the earth close together, sometimes connected by horizontal beams.

pampas grass (material)

Material comprising the stem and leaves of the grass species Cortaderia selloana, used for making ropes and baskets.

panel (wood by form)

Wood in the form of broad, thin, flat or sometimes curved pieces that serve as a support for media in visual works; examples are paintings on wood. In architecture and other constructive arts, use "panels (surface components" to refer to a panel, whether of wood or another material, that is typically a compartment of a surface either sunken below or raised above the general level, and set in a molding or other border, as in a frame, sometimes of different color or material.

panel painting (image-making)

Refers to the activity of painting portable paintings on wood from the painting of other types, such as mural paintings and manuscript illuminations, especially with reference to the Medieval and Early Renaissance periods.


Wall coverings consisting of panels of wood or other material joined in a continuous surface.

panels (surface components)

Distinct portions, sections, or divisions of a surface, especially when sunk below or raised above the general level or enclosed by a frame or border. Common on walls, ceilings, and doors, and also on furniture pieces.


In ancient architecture, a term used to describe a flat tile or tegula. In modern usage, an S-curved roofing tile, laid so the down curve of one tile overlaps the up curve of the next one.

papier mâché

Composite material used for molding objects; made of repulped or pulverized paper and a liquid adhesive binder. May also comprise strips of paper, sometimes reinforced with textiles, stuck together with a wet adhesive, and used to form an object. The object becomes solid when the paste dries; the object may then be sanded, lacquered, and painted. Such objects are very durable; they first developed in Asia and were common in Europe and elsewhere since the 17th century.

papyrus (fiber product)

A writing material prepared from thin strips of the pith of the papyrus plant laid together, soaked, pressed, and dried.

paragon (marble)

Black marble quarried in Greece and Egypt, used as a touchstone and from the late 16th century in Verona used for painting on.


Low walls, projecting from the edge of platforms, terraces, or roofs, or surmounting the cornices of a building; also, walls forming the uppermost part of defensive walls or ramparts.


Marquetry executed in a geometrical pattern, used especially for floors.

particle board

A composite wood board made from small wood chips mixed with a water-insoluble adhesive, then compressed into a dense solid panel. Particle boards were originally made in 1915 as wallboards. The most common adhesive in particle boards is urea formaldehyde glues are used which release volatile formaldehyde. Some particles boards are made with polyurea or phenolic resins. Particle boards are water-resistant, insect resistant, and dimensionally stable during humidity and temperature fluctuations. Particle boards are commonly used in the construction of inexpensive furniture, cabinetry and mobile homes.

paste (glass)

A brilliant glass of high lead content used for the manufacture of artificial gems; also an imitation gem made of this material.

paver (material)

Any brick, tile, stone, or other material fabricated in shaped units and used for paving.

paving asphalt

Natural or modified asphalt or an asphalt aggregate intended for use as a binder in asphalt concrete.

paving brick

A vitrified brick, especially suitable for use in pavements where resistance to abrasion is important.

paving stone

A block or chunk of stone that is shaped or selected by shape for a paved surface.

paving tile

Tile designed to be used for areas of pavement.


A white or drab yellow marble with purplish veins, it was supposedly favored by the emperor Hadrian. The word pavonazzo means peacock blue, violet, or purple in Italian. The ancient marble is also known as Phrygian marble because it is believed to have come from Phrygia in Asia Minor.

pea gravel

Small-diameter (6.4 to 9.5 mm or 1/4 to 3/8 in.) natural gravel, screened to specification.

pearl (animal material)

A smooth round bead formed primarily within the shells of two distantly related groups of molluscan bivalves or clams, including the ocean-dwelling pearl oysters and the freshwater river mussels. Pearls are used in jewelry and for other ornamental puposes; they are considered a gem.

pebble (rock)

A rock fragment, generally rounded by abrasion, larger than a granule and smaller than a cobble; it has a diameter in the range of 4 to 66 mm, or a size between that of a pea and that of a tennis ball.

pebble dash

Textured surfaces made from mortar with small stones embedded in it, used as a coating for walls or floors.

pecan (wood)

Wood of the species Carya illioensis, native to the southeastern United States and Mexico having reddish brown heartwood with dark brown stripes. It is used for interior millwork, handles, and other items.


Plants which remain green and leafy throughout the year, usually with new herbaceous growth from perennating parts.

perforated brick

Brick with vertical perforations or holes; the addition of holes decreases the weight of the brick without significantly reducing its strength.

permanent white

An unstandardized name for certain white pigments, referring often to blanc fixe, zinc white, or mixtures of barium sulfate with zinc white.

pewter (tin alloy)

Alloy of tin and various proportions and combinations of lead and antimony, and sometimes also copper.

photovoltaic cells

Devices in which electromagnetic radiation is generated by a potential at a junction between two types of material, upon absorption of radiant energy.

Picea (genus)

Genus of around 35 species of coniferous evergreen trees in the family Pinaceae, order Pinales, found in northern temperate and boreal. Mature trees may be 20-60 m (66-200 feet) tall. They are distinguished from similar genera by whorled branches, conical form, with needle-like leaves attached singly to the branches in a spiral fashion, and rough rather than smooth branches. As needles are shed throughout the life of the tree, the branches retain a rough appearance from the pulvinus, to which the needles had been attached. Comprises around 40 species of evergreen ornamental and timber trees native to the temperate and cold regions of the Northern Hemisphere. They are pyramidal trees with whorled branches and thin, scaly bark.

Picea sitchenis (species)
No description is available for this term.

pierced walls

Masonry walls in which material has been removed without jeopardizing structural integrity, either for decorative or structural reasons. Masonry walls in which material has been removed without jeopardizing structural integrity, either for decorative or structural reasons.


Any relatively insoluble organic, inorganic, natural or artificial substance that imparts a color to another substance or mixture and always appears as the same specific color when viewed in white light. It is the constituent of paint or ink that provides the color. Distinguished from a dye, which is soluble in the vehicle, a pigment is insoluble in the vehicle, but instead is held in a suspension.

pilaster brick

A brick for constructing pilasters or slightly projecting piers, the end of which is so notched or rebated that it bonds more readily with the backing, thus increasing the stiffening of the wall.

piles (structural elements)

Timber, steel, or precast concrete columns serving as subsurface supports for vertical loads; distinct from "piers (foundation components)" which are larger and are never clustered.

pin oak (wood)

Wood from the species Quercus palustris, native primarily to bottomlands and moist uplands of eastern North America, but found as far west as Oklahoma and Ontario, Canada. It is a reddish brown hard wood that shrinks and cracks with drying; sometimes sold as red oak for flooring and lumber, but it is weaker and contains more knots.

pine (wood)

Wood from numerous trees of the genus Pinus. Pine is used largely in the construction and paper industries, although it is also a source of turpentine, resins, and oils, among other products.

pine tar

Wood tar produced by distilling pine wood, used in wood preservatives and medicinal products.

pink granite

Granite with a mineral composition that results in a pink color.

pink marble

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

Pinus (genus)

Genus containing about 90 species of ornamental and timber evergreen conifers in the family Pinaceae.

Pinus ponderosa (species)

Species of widespread and variable pine native to western North America and widely cultivated elsewhere for its timber and for ornament.

pipe clay

A type of fine white clay used to make tobacco pipes and fine earthenwares.


A building material consisting of stiff earth or clay forced in between forms.

plain sawed lumber

Wood cut at a tangent to the annual growth rings.

plank (wood)

Wood in the form of long, wide, square-sawn, smooth, flat pieces. A plank is typically characterized by being a length of timber sawn for building or other purposes to a thickness of from two to six inches, a width of nine inches or more, and eight feet or upwards in length.

plant material
No description is available for this term.

planters (containers)

Any of various containers in which plants are grown or placed for decorative purposes.


Refers to a soft, plastic material that can be spread or daubed on a wall, ceiling, or other surface, where it afterwards hardens. In the context of art and architecture, it generally refers specifically to a mixture of water, lime, and sand, often combined with other materials, such as animal hair, to give the resulting material strength, texture, and if the surface is to be painted, porosity.

plaster of Paris

Calcium sulfate hemihydrate, a white powder, which sets rapidly upon the addition of water; used for molds, sculpture, casts.

plasterwork (visual works)

Visual works made of plaster, which is a soft, plastic material, in this context usually a mixture of water, lime, and sand, often combined with other materials, such as animal hair. Plasterworks are either applied smoothly to a surface or as a combination of high-relief, sculptural, and surface decoration.

plastic (organic material)

A general term for any of a large and varied class of natural or synthetic organic materials that can be molded, extruded, or cast when soft or liquid, and then set into a rigid or slightly elastic form. Natural plastics include tree resins, beeswax, gutta-percha, horn, and clay. Synthetic plastics were first made in the 19th century. Plastics are used widely in manufacturing.

plastic laminate

Resin-impregnated materials, such as paper or fabric, produced under heat and high pressure to form an insoluble homogeneous piece. Laminates were first made in 1907 by Leo Baekeland when he coated canvas with phenol formaldehyde. Distinguished from "laminated plastic" which is a thin sheet of superimposed layers of plastic bonded or impregnated with resin and compressed under heat.

Platanus acerifolia (species)

Species that is a hybrid of Platanus occidentalis and Platanus orientalis. It combines characteristics of both in varying degrees. It is a little shorter and more squat than the American (occidentalis) tree and usually has bristly, paired seedballs. There are variegated forms of London plane. It is planted widely in cities for its resistance to air pollution and to diseases that more readily affect other plane trees.

Platanus occidentalis (species)

Species of plane tree native to North America; the tallest of the plane trees, reaching more than 50 m (160 feet) in height. Its pendent, smooth, ball-shaped seed clusters usually dangle singly and often persist after leaf fall. It is distinguished from other trees by its mottled exfoliating bark, which flakes off in great irregular masses, leaving the surface mottled, and greenish-white, gray and brown. For trees known simply as "sycamore," use Acer Pseudoplatanus, which is a species of maple.

plate glass

Any glass that has been rolled or cast into a sheet and then ground and polished.

platform frames

Wood structural frames in which the studs are only one story high, the floor joist of each story rests on the top plates of the story below or on the foundation sill for the first story, and the bearing walls and partitions rest on the subfloor of each story.

platinum (metal)

Pure metallic element having symbol Pt and atomic number 78; a lustrous, malleable, ductile, silvery white metal, considered a precious metal. Use also for this metal as processed and formed, usually in combination with other substances, to make objects and materials.

Plexiglas (TM)

Proprietary name for polymerized methyl methacrylate, used as a substitute for glass in products such as windows, skylights, illuminated signs, and aircraft. Plexiglas was trademarked by Rohm and Haas AG in Germany ca. 1930s.

plinth brick

A brick beveled on its face or end to provide for the reduction in thickness between the plinth and the main part of a wall.

plug tobacco

Chewing tobacco produced in the form of a flat cake.

plum (fruit)

Drupe, or stone-fruit, from several trees of the genus Prunus. The plum usually has red, purple, or yellow skin, and when ripe, a powdery bloom.


Wood board consisting of a number of thin layers of rotary-cut veneers glued together so that the grain of each layer is at right angles to the grain of the adjacent layer.


Thermoplastic polyester used in glazing, including bullet- and explosion-resistant laminates.

polyester (resin)

Resin formed by the reaction between dibasic acid and dihydroxy alcohol.


A group of polyolefin polymers derived from ethylene by polymerization by heat and pressure.

polygonal masonry

Building material comprising uncoursed masonry used in the ancient Mediterranean world. Laid up of large blocks of stone in rough polygonal shapes, often fitted together without mortar. Similar to "cyclopean masonry," but with more precise fitting of stones due to the straight hewn sides.


A clear plastic or stiff foam, a polymer of styrene, used chiefly as an insulator in refrigerators, air conditioners, and for packaging.


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.