A Set of Six Chinese Export Pith Paper Pictures of Birds,
Circa 1840-60.
Gouache (from the Italian guazzo, "water paint, splash") is a type of paint consisting of pigment suspended in water. Gouache differs from watercolour in that the particles are larger, the ratio of pigment to water is much higher, and the presence of an inert white pigment such as chalk. This makes gouache heavier and more opaque, with greater reflective qualities.[1]
Pith paper is commonly mistaken as rice paper. Pith comes from the central column of spongy cellular tissue in the stem of a small tree called Tetrapanax Papyrifera, native to south-west China. It has had a variety of uses, some going back many centuries. At the imperial court both men and women wore coloured flowers made from pith in their hair. It has been used to produce toys for children and in craftwork. It is still sold as Chinese medicine to make a diuretic infusion. For use in painting, it is cut by hand with a knife into thin sheets from short lengths of the spongy tissue. Cutting is highly skilled and the constraints of the process mean that the finished sheets for painting seldom, if ever, measure more than about 30cms by 20cms. The sheets are dried, trimmed and used for painting without any further processing.
Because of the nature of pith and its cellular structure, the gouache used by the Chinese sat on the surface and produced a bright and even sparkling effect. Very fine detail could be achieved but pith did not lend itself to the flat wash of colour favoured for European watercolours