M. (madder - marmorino)

Madder - A natural red dye obtained from Rubia tinctorium, a perennial herb cultivated in Europe and Asia Minor. The cultivation of madder spread to Asia Minor about the 10th  century; it was introduced into Europe by the 13th. The dye contains three principle colouring components: alizarin (red), purpurin (red) and xanthine (yellow). The colours are extracted from the dried, powdered root as a precipitate when it is boiled in water. Alum lakes of madder, madder lake and rose madder, were used as artists pigments. Madder forms a bright red colour when precipitated on aluminium hydroxide. Tin, chromium and iron mordants can produce purple, brown and pink colours. After commercial introduction of the synthetic alizarin in 1871, the natural product was no longer used, though natural rose madder was still used occasionally as a lake for artists' colours. Madder lake  is listed among the pigments used for colouring stucco marble in the nineteenth and twentieth century. The presence of purpurin along with alizarin has been used to distinguish natural madder dyes from the synthetic alizarin dyes. Purpurin fluoresces a bright yellow-red while alizarin produces a pale violet colour.
Synonyms: madder lake; alizarin (natural); purpurin (natural); xanthine (natural); garancine; Pigment Red 83; CI 58000:1; Natural Red 9; CI Nos. 75330, 75420; dyer's root; Farberröte (Ger.); Krapplack (Ger.); laque de garance (Fr.); lacca di robbia (Ital.); laca de rubia (Sp.); rose madder; Turkey red
Wittenburg (1999); Museum of Fine Arts, Boston (2000)

Magnesian limestone - Permian limestones which have had their chemical composition naturally altered with the calcium content being replaced by magnesium. Fine grained and varying from yellow/brown to cream in colour, although  they weather to a dark grey. 
Synonyms: magnesium limestone
English Heritage (2000); Museum of Fine Arts, Boston (2000)

Malachite  CuCO₃-Cu(OH)₂  -   An opaque green mineral composed of basic (hydrated) copper carbonate with pronounced, often concentric, banding. It has a Mhos hardness of 4. Malachite occurs naturally with the blue copper carbonate mineral called azurite with malachite being the more abundant of the two. Major deposits of the copper ores have been found in Siberia (Nizhne-Tagilsk), France (Chessy), Nambia (Tsumeb), and the U.S. (Bisbee, Arizona). Both malachite and azurite have been used as gemstones and paint pigments since before 3000 BCE. Malachite is prepared as a pigment by careful selection, grinding, washing and levigation. Coarsely ground malachite gives a dark green colour while finely ground particles give a lighter more transparent tone. Malachite 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 green verditer, tends to have regularly sized particles with rounded edges. The colour is paler than malachite. It was rarely used in fine art paintings, but rather for both distemper and oil based interior house paints in the 19th century. It is listed among the pigments used for colouring stucco marble in the nineteenth and twentieth century.
Synonyms: basic copper carbonate; basic cupric carbonate; green hydrous copper carbonate; green bice; Bremen green; green verditer; Hungarian green; mountain green; mineral green; copper green; iris green; Olympian green; Berggrün (Ger.); Malachit (Ger.); verdetto della Magna (It.); malachito (It.) malaquita (Sp.); malachite (Fr.); rokusho (Jap.); shih lü (Chin.)
Wittenburg (1999); Museum of Fine Arts, Boston (2000); Trench (2000)

Manganese oxide MnO -  1. Manganese oxide is a general name for the various oxide forms of manganese: such as manganese oxide (MnO), manganese dioxide (MnO2), manganese sesquioxide (Mn2O3) and  manganese tetroxide (Mn3O₄). 2. Manganese oxide (MnO) is a bright green powder that can be oxidised to form the other manganese oxide compounds. 
Synonyms: manganous oxide; manganese monoxide
Museum of Fine Arts, Boston (2000)

Man made material  - A material or combination of materials manufactured by human effort, or fashioned into shape by man or a man made industrial process (excluding metal). 
English Heritage (2000)

Marbelite - A synthetic, mouldable, artificial marble. Marbelite is made by heating potassium alum in water then added 10% heavy spar and marble dust (Brady 1971). It is cast into rubber moulds.
Synonyms: artificial marble
Museum of Fine Arts, Boston (2000)

Marble  CaCO₃ -  A hard, dense, crystalline stone primarily composed of calcium carbonate. Marble is limestone or dolomite that has been metamorphosed with heat and pressure. Pure calcite marble is white, but impurities produce a wide variety of colouring and patterns. Marble has fine grains and polishes to a smooth, high gloss. It is used for statuary and buildings. Marble has been quarried from sites around the world. Mayer (1969) lists the following locations and types of marbles:  - Greece: Parian marble, Pentelic marble, rosso antico, Eleusinian marble - Italy: Carrara marble, bardiglio, cipolin, parmazo marble - Belgium: rance, Belgian black, St. Anne marble - France: Languedoc marble, griotte, Sarrancolin marble     - U.S.: Vermont white statuary, Georgia white, Colourado Yule statuary, Alabama cream, Tennessee pink, Rockingham royal black.
The technique used in the production of scagliola, which employs coloured mixes of gypsum plaster and small chips of stone, was developed to imitate the rich colour of pietre dure.
Synonyms: calcium carbonate; Marmor (Ger.); marbre (Fr.); marmo (It.) marmol (Sp.)
Museum of Fine Arts, Boston (2000); Mayer (1969); Trench (2000)

Marble dust - Marble chips that have been crushed to form a powder. Marble dust is used as an inert pigment and filler in paints. Even as a fine powder, some of the crystalline surfaces reflect light adding a sparkle to regions in which it has been added to the plaster used in a fresco support.
Synonyms: marble meal; marble grit
Museum of Fine Arts, Boston (2000)

Marble-gypsum -  An alternative name for alum-gypsum. 
Wittenburg (1999)

Marezzo marble - A similar material to Scagliola, also used to imitate marble, but relying entirely on pigments rather than stone aggregates for effect. Coloured Keeneís cement or gypsum plaster is used, together with animal glue and pigments, if a coloured marble is being copied. Frequently marezzo was cast on smooth sheets of slate or glass to give a polished surface; some polishing with pumice stones then followed. However, as the mould itself creates a reasonably smooth surface, the polishing process is not as lengthy as that for scagliola and thus marezzo is easier to produce. It was sometimes used for small areas of external cladding. 
Ashurst (1983); Trench (2000)

Marmorino - A mortar prepared from lime mixed with marble dust. It is mentioned as one of the historic technique for decorating architectural surfaces.
Synonym : marmorina
Paolini and Faldi (2000); Wittenburg (1999)
 
 

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