P. (paint - pitch)

Paint - Any pigmented liquid, liquefiable, or mastic composition designed for application to a substrate in a thin layer which is converted to an opaque solid film after application. Paint applied to masonry may be solvent or water based, or may be a masonry paint of a slightly cementitious nature specially formulated with various types of aggregate or thickening agents to smooth rough or uneven masonry walls. Colour washes based on lime, such as whitewash, although not technically considered to be paint, and colour stains which do not form a film on top of the masonry, but instead penetrate into the masonry substrate, have traditionally provided many of the same benefits as paint.
Grimmer (1984)

Paraffin wax - A white, translucent odourless hydrocarbon wax that is chemically inert. Paraffin was first produced commercially in 1867 as a refined petroleum product composed of a mixture of saturated straight chain hydrocarbons (C₂₂-C₃₆). Production consists of separation by distillation followed by chemical treatment and decolorisation. Synthetic paraffin wax made from coal products was introduced after World War II. The snow-white synthetic paraffin is harder and purer than petroleum-based paraffin waxes. Paraffin is used to make sealing materials and for masonry and concrete treatment. Microcrystalline wax is a special refined grade of paraffin wax. 
Synonyms: microcrystalline wax; paraffin scale
Museum of Fine Arts, Boston (2000)

Paraform -   Paraformaldehyde, an additive used with wood flour as a hardener in adhesives. See also resorcinal resin adhesive. 
RS Means Building Glossary (undated)

Parchment - A material made by stretching a wet skin, usually calf-, deer-, goat- or sheepskin, which has been unhaired using lime, on a framework and allowing it to dry in the untanned condition under tension. Often the grain layer is scraped away, using a special knife, and the surfaces are then treated with hot water, chalk and other materials to remove grease and give a more uniform substrate.
Trench (2000)

Parchment glue - A jelly-like, water soluble product of cooked parchment scraps. Parchment glue is composed of gelatin. 
Synonyms: parchment size
Museum of Fine Arts, Boston (2000)

Parchment size - Parchment size is listed as one of the organic additives used for stucco marble preparation according to literature.  In particular, parchment size is defined as gelatine made from parchment waste. See also : parchment glue.
Wittenburg (1999); Museum of Fine Arts, Boston (2000)

Pargeting  (Pargetting or Parging) -  External decorative plasterwork often incised or modelled with ornamental impressions or patterns made with a mould or comb. It consists of a tough lime plaster, made of lime putty or mixtures of lime and gypsum plaster, reinforced with ox hair, and with tallow sometimes added as a plasticizer and a water-repellent. The surface of the pargeting was frequently limewashed; occasionally linseed oil or wax was used as a protective coating. It was usually applied to timber-framed houses, especially during 15th  and 16th centuries in south-east England. 
Ashurst (1983); Grimmer (1984); Trench (2000);  English Heritage (2000)

Parian cement - Patented J. Keating 1846. A hard finish plaster used for interior stucco decoration. It was similar to Keene's cement plaster, except borax was used as an additive to finely powdered gypsum in place of alum, to accelerate the setting. Plaster of Paris was soaked in a solution of borax (sodium borate), cream of tartar (potassium hydrogen tartrate) in water and subsequently calcined. Parian cement was free working and possessed good tensile strength. It had high strength and could be polished. It was a hard-finish plaster, used  neat for mouldings over a float coat of one part Portland cement to three parts sand. It was also used for flooring and for imitation tiling, as well as for sgraffito.
Synonyms: gypsum cement; hard-finish plaster
Ashurst (1983); Museum of Fine Arts, Boston (2000);  RS Means Building Glossary (undated); Trench (2000)

Pearlite - A eutectic structure of cast iron composed of alternating layers of ferrite and cementite. Pearlite occurs when the carbon content reaches 0.8% (Scott 1991). It is commonly found in ancient steels.
Museum of Fine Arts, Boston (2000)

Pebble  -  Rock fragment (diameter 4-64mm) larger than gravel and smaller than cobble, combined with other  material e.g. flint, for decorative effect.
English Heritage (2000)

Pebbledash  -  A render with small washed stones added as aggregate. Popular in the early 20th  century. 
English Heritage (2000)

Penetrant -   An additive that increases a liquid's ability to penetrate a surface or enter the pores of a substrate. Penetrants are typically used as wetting agents. 
RS Means Building Glossary (undated)

Perlite -  1. A eutectic material formed between ferrite and cementite. 2. A type of obsidian found in California that is 70-75% silica, 12-14% alumina and 6-8% alkalis. Perlite contains a high proportions of cracks, spheroids and water. When it is flash roasted to 1000*C, perlite expands to 20 times its size forming bubble-filled beads. This white aggregate is then crushed and used as an extender. Expanded perlite is also used to make insulating bricks.
Synonyms: Pearlite
Museum of Fine Arts, Boston (2000)

Persian berries - Persian berries, also called buckthorn berries, are small berries from any shrub of the buckthorn family, such as Rhamnus infectorius, R. amygdalinus, R.oleodies, or R.alaternus. Buckthorn plants are native to the near East and have been cultivated in Europe since Roman times. A water-soluble dye was extracted from the berries for use in lake pigments. The unripe berries produce a yellow juice or sap that is used for making a yellow pigment called sap green. The ripe berries were used to make Dutch pink, a yellow lake. The principle colorant, rhamnetin, is extracted from the dried berries by boiling water. Some plants also contain other colorants such as kaempferol (R.cartharticus), quercetin, xanthorhamnin and emodin. Sap green lake is made with alum and can vary in colour from yellow to green. A fugitive yellow colour prepared on alum was widely used in house paints in England in the 18th century. Persian berries are listed among the additional pigments used for colouring stucco marble in the nineteenth century.
Synonyms: French berries; buckthorn berries; dyer's buckthorn; Persian berry lake; yellow berries; sap green; Dutch pink; grain d' Avignon (Fr.); Avignon berries; Gelbbeere (Ger.) Spincervino (Ital.) Espino cerval (Sp.); Persische bessen (Dut.); rhamnetin
Wittenburg (1999); Museum of Fine Arts, Boston (2000)

Pigments  -  A coloured powder which, unlike dye, is insoluble. When they are mixed in large amounts with a clear binding medium, pigments become paint, but they can also be added in small quantities to fluid materials to act as colouring agents. A limited range of pigments, including ochres, umbers and some inorganic pigments such as cobalt blue, chrome green and chrome yellow, can be used to colour lime mortars, concrete and plaster. Early literature has indicated that mineral pigments as well as organic dyes were used for the coloration of stucco marble.  Usually, different manuals recommended choosing the pigments used for frescoes - resistant to light and to the caustic action of lime - even though this was not always the practice, especially in the nineteenth and twentieth century.  During the baroque period, the pigments recommended were those used for fresco paintings. Mixtures containing organic dyes have been much less used than mineral pigments because natural dyestuffs tend to fade.  Organic dyes (tannins from gall-nuts, brown wood, logwood, walnut husk for black marble imitation) were typically used for dark colours. In the twentieth century, coloration was obtained by chemical reaction involving copper vitriol, iron vitriol, gypsum and alum with lime.
Trench (2000); Wittenburg (1999)

Pitch - A sticky, black residue obtained from the distillation of coal tar, petroleum or pine tar. Pitch is used as a sealant as well as a component in roofing and water proofing. 
Synonyms: Burgundy pitch; Canada pitch; Jew's pitch
Museum of Fine Arts, Boston (2000)
 
 

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