Thangka means literally "thing that unrolls". Painted images served the same purpose as the gilt bronze statues but perhaps more effectively: to focus the mind of the practitioner, thus aiding concentration and merging consciousness with the deity; to gain merit for the donor; and to satisfy an obligation in an established system of gift-giving, especially between the Tibetans, Chinese and Mongolians. The production of the paintings was largely prescribed and followed consistent steps. The fabric ground was temporarily stretched, then prepared with sizing of proteins and organic matter. When the ground was sufficiently smooth, a preparatory layer of chalk (or kaolin, white porcelain clay) mixed with water was applied with a knife. The surface, front and back, was polished with a small stone or shell. The painter traced a network of fine geometric lines using a chalk line or compass, which corresponded to diagrams developed for each deity and secondary figures; proportions were established by ancient Sanskrit texts. Colors were derived from finely ground minerals (blue from azurite; green from malachite; reds and yellows from cinnabar, vermilion, realgar, or orpiment; orange from red lead; white from chalk), and were enhanced by gold and black outlining from graphite or burnt wood. "Opening the eyes" of the divine figures was among the last steps, and was an integral part of the consecration ritual.