PAINTING MATERIALS
production soon after 1935 for use in printing inks and paints, it is not known
that it has been used, as yet, in artists' paints. Because of its brilliant color and
other desirable properties, however, it may be expected soon to find use for that
purpose.
Monastral Blue (see Phthalocyanine Blue).
Mordant is a general term for a fixing agent. It is derived from the Latin,
morderey 'to bite.' In dye processes, the term is used to indicate certain chemicals
which are used for fixing colors on textiles by adsorption. The more common
mordants are the soluble salts of aluminum, chromium, iron, tin, etc., which are
precipitated on the fibres along with the dye by an alkali. These mordant salts
are particularly necessary for fixing adjective dyes tuffs to fibres. Occasionally,
the term applies to the base or substrate employed in the preparation of lake
pigments from organic dyes (see Lake). In the technical language of the fine arts,
the term refers to the adhesive film used to fix gold leaf in one type of gilding
(see also Mordant, p. 35).
Mosaic Gold is artificial tin (stannic) sulphide (SnS2), and it is made by
combining tin with sulphur in various ways (see Colour Index., p. 306). This
sulphide, which looks like bronzing powder, consists of fine, soft, yellow scales
with a golden glint. It was formerly used for gilding purposes as a sort of gold
substitute. According to Thompson, who has described the preparation and his-
tory of this material (The Materials of Medieval Painting, pp. 182-184), it was
known in Europe as early as the XIII century. There are many recipes for making
it in XIV and XV century texts, and it is found occasionally on mediaeval manu-
scripts. In the Bolognese MS. (XV century), a whole chapter is given to the
preparation of mosaic gold or 'purpurino9 and its use in painting (see Merrifield,
II, 458). Stannic sulphide is a fairly stable compound; it is unaffected by light
and by mineral acids, but is soluble in sodium hydroxide and in aqua regia.
Mountain Blue (see Azurite).
Mountain Green (see Malachite).
Mummy* A brown, bituminous pigment was once actually prepared from the
bones and bodily remains of Egyptian mummies which had been embalmed with
asphaltum (see Church, p. 236, and Eibner, Malmaterialienkunde, p. 213). It was
claimed that, through time, the asphaltum had lost some of its volatile hydro-
carbons, and the powder from the ground-up, embalmed remains was more solid
than recent asphaltum and was better suited for a pigment. Apparently, it was
once a favorite with some artists. Church says (p. 237) that it was certainly used
as an oil paint at least as early as the close of the XVI century. Little is known
about its history; it has not been mentioned in reports on the identification of
materials in paintings. It is now perhaps unobtainable and is no longer desired
in the arts. Some oil paints sold under that name are substitutes which contain
bituminous earths like Van Dyke brown. The microscopic character of true
mummy has not been described, but probably its properties and behavior are
much like those of asphaltum (see Asphaltum).