Dunhuang frescoes are painted with what medium to adjust the color?

Dunhuang murals are traditional Chinese cave murals, the production process includes the production of the ground battle layer and painting two steps, painting is the use of gum color painting technology, is to use plant gum (peach gum) and pigment powder made of pigment to paint, Dunhuang murals painted through the Wei Jin, Sui and Tang, Song, Yuan, Ming and Qing dynasties, before and after the time span of more than a thousand years, each period has its own technical characteristics and fixed color.

In general, Dunhuang murals use pigments to natural mineral pigments (not excluding the use of a number of plant organic pigments, and synthetic pigments), different colors of pigments of different chemical composition, the source of different, in general, iron oxide pigments used more, the source of such pigments is the composition of iron oxide clay, including ochre, earth yellow, brown, earth red, and so on; there is also a typical stone green, like stone green is also a typical stone green. Like stone green stone green is also a typical use of color, stone green is the main source of blue copper ore, stone green is the main source of malachite; white for the lime white (calcium carbonate), red also used artificial smelting of lead, vermilion and so on (the generation of this type of pigment is related to the ancient alchemy, the earliest product of the chemical industry).

The common method of pigment production is that the minerals are first crushed and ground into different granularity of the color paste with water (lime green is divided into head green, two green, three green, referring to the different granularity of lime green, the finer the particles, the lighter the color), and then mix it with vegetable gums, which became the pigment.