Glossary.  Materials used in 19th and 20th century Plaster Architecture.
By: JoAnn Cassar and Roberta de Angelis 
 

A. (alum- azurite)
 

Alum - A general name used for aluminium sulphate salts. Most commonly the term alum, or potash alum, refers to aluminium potassium sulphate. It is a colourless, crystalline material. Other materials referred to as alum are aluminium sulphate or the mixture of aluminium sulphates obtained by treating pulverised bauxite with sulphuric acid, ferric ammonium sulphate, chromium sodium sulphate and chromium ammonium sulphate. Alum is listed among the inorganic additives used for stucco marble preparation according to literature. See also : alum-gypsum.
Synonyms: aluminium potassium sulphate; aluminium ammonium sulphate; aluminium sulphate; alum cake; alunite.
Wittenburg (1999);   Museum of Fine Arts, Boston (2000)

Alum-gypsum - It is a mixture of CaSO4 with alum ­ i.e. plaster of Paris soaked with alum solution, then burnt again and finely ground.  After setting, it obtains high mechanical strength and hardness.  According to Leixner, alum-gypsum, also called marble-gypsum, has been primarily used up to the 1960s.
Wittenburg (1999); Leixner (1993) 

Aluminous cement -   See cement. 
RS Means Building Glossary (undated)

Ammonium carbonate - A white powder that smells strongly of ammonia. Ammonium carbonate slowly decomposes in air to form ammonia and carbon dioxide. It is used in ammonium casein glue. Ammonium carbonate is commonly called hartshorn because it was historically prepared by the destructive distillation of the antlers from harts (red deer). Hartshorn is actually composed of a double salt of ammonium bicarbonate and ammonium carbamate. 
Synonyms: hartshorn; volatile alkali; carbonate of ammonia; smelling salts; crystal ammonia; ammonium sesquicarbonate; sal volatile; rock ammonia.
Museum of Fine Arts, Boston (2000)

Anhydrite CaSO4 - A naturally occurring mineral of anhydrous calcium sulphate that is often found in gypsum deposits. Anhydrite was first identified as a mineral in deposits at Innsbruck, Austria. Anhydrite can be transparent or translucent and has a lustrous sheen. It occurs in several colours such as white, grey, blue, pink, red and lavender. Anhydrite was used in ancient Egypt for carved objects and vessels, many of which are in the shape of animals (Fay, 1998). It is used in the manufacture of Portland cement to control the set.
Synonyms: blue marble; calcium sulphate.
Museum of Fine Arts, Boston (2000); RS Means Building Glossary (undated)

Anhydrous lime -     See lime. 
RS Means Building Glossary (undated)

Animal black - An impure black carbon pigment prepared from burnt animal bones. Animal black, or bone black, contains about 10% carbon along with 84% calcium phosphate with smaller amounts of magnesium phosphate and calcium carbonate. The blue-black pigment is denser than carbon black and has a good working quality for oil paints and watercolours. A fine particle grade of bone black is now sold as ivory black and an inferior grade has been sold under the name of Paris black. Drop black is dried lumps formed after bone black is mixed with water and glue. Drop black was commonly used in the 19th  century for house paints. 
Synonyms: bone black; ivory black; drop black; Frankfort black; German black; Pigment Black 9; CI 77267; Paris black; abaiser.
Museum of Fine Arts, Boston (2000)

Animal glue - A strong, liquid adhesive consisting primarily of gelatin and other protein residues of collagen, keratin or elastin. The primary amino acids in animal glues are: glycine (24.7%), proline (13%), analine (10.1%), glutamic acid (9.7%), arginine (8.2%) and hydroxyproline (7.4%) (Mills and White 1994). Gelatin (size) is similar to glue, but purer and better refined. Animal glue has been made from ancient times from bones, skins and intestines of animals (fish, goats, sheep, goats, cattle, horses, etc.). These agglutinating materials are hydrolysed and broken down in boiling water; the cooled solution yields a jelly-like substance which is gelatin or glue. The water soluble glue occurs in a wide variety of forms and colours ranging from transparent to opaque and white to brown. Glue is soaked in cool water to form a turbid jelly that will become clear and thinner with gentle heating. Glue will decompose and darken when it is boiled. Top-quality animal glues are made from rabbitskin, sturgeon bladders and parchment clippings. Hide glues are used in the manufacture of  gessoes, gilding and paints. Animal glues are available as, pellets, hot melts or a liquid solutions (with a plasticizer or preservative).
Synonyms: glue; gelatin; size; isinglass; fish glue; bone glue; parchment glue; Cologne glue; calfskin glue; nikawa; hide glue; rabbitskin glue; sturgeon glue; pearl glue; carpenter's glue; scotch glue.
Museum of Fine Arts, Boston (2000)

Antifreeze - An additive used to lower the freezing point of a liquid. When added to fresh mortar or rendering, the anti-freeze additive increases the rate of heat evolution by accelerating the set. The additive is here often calcium chloride.
Ashurst (1983); Museum of Fine Arts, Boston (2000)

Aqua regia -  Common name for an acid mixture that contains 3 parts hydrochloric acid and 1 part nitric acid. Aqua regia was used to produce tin chloride, also called killed spirits, in the 18th century. This dark red colorant was made by dropping a block of tin in the aqua regia solution. Aqua regia will dissolve all metals except silver.
Synonyms: nitrohydric acid; yellow fuming liquid; nitro-muriatic acid; nitrohydrochloric acid; chloronitrous acid; chlorazotic acid.
Museum of Fine Arts, Boston (2000)

Architectural coating - A paint or varnish designed for use on the interior and exterior of buildings. Architectural coatings are used for protection and decoration on residential, commercial, institutional and industrial buildings. Under normal weathering and use, the lifetime of an architectural coating is expected to be 5-20 years.
Museum of Fine Arts, Boston (2000)

Argillaceous limestone - A limestone that contains a significant amount of clay. Argillaceous limestone is used in cement manufacturing.
Synonyms: pelitic; cement rock.
Museum of Fine Arts, Boston (2000)

Artificial marble -  A synthetic, moulded stone prepared to imitate the appearance of marble. One type of artificial marble, called Marbelite, is made by heating potassium alum in water then adding 10% heavy spar and marble dust (Brady 1971). Another type of artificial marble, called Exsilite, is made by fusing grains of silica and pigments to form a slab that simulates onyx marble. Artificial marble is one historic technique for decorating architectural surfaces.  Other techniques besides artificial marble are scagliola, stucco marble, stucco lustro and marmorino. See also : artificial stone
Synonyms: Marbelite; Exsilite.
Brady (1971); Wittenburg (1999);  Museum of Fine Arts, Boston (2000)

Artificial stone - Any mixture of cement or plaster prepared to imitate the appearance of natural stone. In early Egyptian tombs and Roman buildings, walls were coated with lime and gypsum plaster then painted to simulate the appearance of natural stone (Proudfoot 1996). By the 16th century, recipes for artificial stones included marble dust, lime and glue. Manufacturing centres were preparing cast stones based on terra cotta (Coade Stone) or cement (Pulham stone, Haddon stone) by the mid 19th century for use in buildings, statuary and decoration. Also in the 19th century, various mixtures of modified gypsum plasters, such as Keeneís cement, crushed stone and colouring materials were patented as artificial marbles, many of which were case into slabs for interior decoration.  Cement, mixed with sand and crushed stone, and often referred to as cast, reconstituted or reconstructed stone, was widely used from the late 19th century in Europe and North America to produce balustrades, columns, architraves, arches and tracery windows. Various aggregates such as granite and other stone dusts, slag and crushed brick were used to produce a range of colours and textures; pigments could also be introduced. Artificial stone can often be distinguished from natural stone by its appearance and by the fact that the latter is colder to the touch. More precise identification of the simulant can involve microscopic examination and chemical analysis of its components.
Synonyms: cast stone; reconstructed stone; reconstituted stone; oxychloride cement; renders; Victoria stone; Protean stone; Frear stone; Siliceous Concrete Stone; Coade's stone; Rangerís artificial stone; Permastone; Pulham stone; Haddon stone; Bradstone; Empire Stone; Pulhamite Stone; Guattaris marble; artificial marble; scagliola; marezzo; stucco lustro.
Trench (2000); Proudfoot (1996);  Museum of Fine Arts, Boston (2000);  English Heritage (2000)

Asbestos -  A common name given to any of several fibrous silicate minerals. The most widely used asbestos mineral is a type of serpentine called chrysotile (white asbestos). Other asbestos minerals are: riebeckite, crocidolite (blue asbestos), amianthus, anthophyllite, amphibole, amosite (brown asbestos), tremolite, or actinolite. Asbestos is non-combustible and heat resistant. It was used by the ancient Greeks, Egyptians and Chinese as a fireproof fabric. In the 19th  and early 20th  centuries, asbestos was used for fireproofing and insulating new houses. Small asbestos fibres were mixed with binders and compressed into boards, shingles, tiles and sprayed onto ceilings. Health concerns have limited the use of asbestos since the early 1960s. In the U.S., it was declared a hazardous material in 1986.
Synonyms: amphibole; asbestus; serpentine; earth flax; chrysotile; cork fossil; mountain leather; mountain cork; mountain flax; mineral fibre; amosite; crocidolite; silicate fibre; amianthus; riebeckite; anthophyllite; tremolite; actinolite; salamander wool.
Museum of Fine Arts, Boston (2000)

Ash (residue) - A greyish white to black powdery residue that remains after a substance has burned. The residual ash is composed of non-combustible, or mineral, matter such as silica, alumina, iron oxide, clay, etc. Ash from plant material generally contains high amounts of lime, sodium carbonate and/or potassium carbonate. Wood ash was the principal source for potassium for several hundred years. Phosphorus was obtained from the ash of animal bones (calcium phosphate). Ash from sea plants contains high amounts of iodine.
Museum of Fine Arts, Boston (2000)

Azurite  2CuCO3-Cu(OH)2  - A deep blue mineral composed of basic copper carbonate that is naturally found with the green copper carbonate mineral called malachite. Azurite and malachite have been used as gemstones and paint pigments since before 3000 BCE. They are prepared as pigments by careful selection, grinding, washing and levigation. Coarsely ground azurite gives a deep blue colour while finely ground particles give a lighter more transparent tone. Azurite is lightfast but is sensitive to acids and sulphur fumes. Basic copper carbonate can also be made artificially by colouring chalk with copper sulphate. The synthetic pigment, called blue verditer, blue bice, Bremen blue or ashes blue, tends to have regularly sized particles with rounded edges. The colour is similar to finely ground azurite. It is listed among the pigments used for colouring stucco marble in the nineteenth and twentieth century.
Synonyms: blue verditer; mountain blue; Pigment Blue 30; CI 77420; ashes blue; Bremen blue; blue bice; Armenian stone; lapis armenius; chessylite; blue malachite; mineral blue; basic copper carbonate; basic cupric carbonate; copper blue; chessy copper; bleu d'Allemagne (Fr.); Bergblau (Ger.); Bergasur; Azurit (Ger.); azurite (Fr.); azzurrite (It.); azzurro della magna  (It.); azurita (Sp.); azurium citramarinum.
Wittenburg (1999);  Museum of Fine Arts, Boston (2000)
 

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