Painting oil

Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, and varnish may be added to increase the glossiness of the dried oil paint film. Oil paints have been used in Europe since the 12th century for simple decoration, but were not widely adopted as an artistic medium until the early 15th century. Common modern applications of oil paint are in finishing and protection of wood in buildings and exposed metal structures such as ships and bridges. Its hard-wearing properties and luminous colors make it desirable for both interior and exterior use on wood and metal. Due to its slow-drying properties, it has recently been used in paint-on-glass animation. Thickness of coat has considerable bearing on time required for drying: thin coats of oil paint dry relatively quickly.

The technical history of the introduction and development of oil paint, and the date of introduction of various additives (driers, thinners) is still—despite intense research since the mid 18th century—not well understood. The literature abounds with incorrect theories and information: in general, anything published before 1952 is suspect. Until 1991 nothing was known about the organic aspect of cave paintings from the Paleolithic era. Many assumptions were made about the chemistry of the binders.

The oldest known oil paintings date from 650 AD, found in 2008 in caves in Afghanistan's Bamiyan Valley, "using walnut and poppy seed oils."

Though the ancient Mediterranean civilizations of Greece, Rome, and Egypt used vegetable oils, there is little evidence to indicate their use as media in painting. Indeed, linseed oil was not used as a medium because of its tendency to dry very slowly, darken, and crack, unlike mastic and wax (the latter of which was used in encaustic painting).

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