The unique character of Chinese painting developed as a result of the materials used and the kind of format evolved in ancient times. Painting on silk or on paper calls for fluid ink and water-color pigments, which alone are suitable to these light and absorbent materials. Conversely, the distinctive materials and forms were retained over many centuries and developed by artists because these means alone produced the aesthetic qualities which the Chinese most admired.
The earliest paintings now known, fragments from the fifth to the third century B.C. recovered at Ch'ang-sha in Hunan, are done in ink and light color on silk. For a long time following the invention of paper, traditionally in A.D. 105, silk continued in favor for paintings and good calligraphy. After paper came into more general use as a ground for painting, the choice between the two materials was a matter of the artist's personal inclination. At all times silk has been used more often than paper for highly colored paintings because the relatively heavy pigments adhere better to the more textured surface (no. 15 and no. 5). Silk tends to darken in tone through long exposure to light, so that frequently old pictures, especially the vertical hanging scrolls, are often distinctly somber (no. 6). A nearer approximation to the original pale golden tone is sometimes found on album leaves which have been more protected from light and dirt (no. 33 and no. 34).
Painting silk, prepared with a sizing of alum and glue, unquestionably varied a great deal, regionally and from century to century, in weave, weight, and other characteristics. Although there is considerable material about painting silks in old Chinese texts, it is extremely difficult to correlate textual descriptions with existing examples. The landscape attributed to Kuo Hsi (no. 7), and Hui-tsung Finches and Bamboo (no. 15), for example, are painted on smooth, closely woven silk, while the silk of the fifteenth-century Mountain Landscape -- the Four Seasons (pl. 34) is much more loosely woven. To what extent such differences are historically significant must await further careful study.
Letters and documents written on paper dating from possibly the second and certainly the mid-third century A.D. have been recovered in Central Asia, but as yet no paintings on paper have been found from so early a date. Although a variety of excellent papers were made in the T'ang Dynasty and extensively used for the writing and printing of Buddhist texts, this material probably did not come into general use for paintings and fine calligraphy . . .