An exploration, with 61 illustrations, of the relationship between the structure and physical properties of materials and the aesthetic quality of objects made from them. The artist's fingers physically interacting with matter can no more be neglected than the concept in his mind. Many details are shaped by surface or interfacial tension. Capillarity forms and joins the gold grains in Etruscan jewelry, it restricts the silver drops in Japanese gama hada, it determines the spots in Tang dappled ware, in Shigaraki ware and in oil-spot temmoku. It forms the glaze on Egyptian frit. It binds the sand or clay in a porous mold and it restrains molten metal. If the balance of interface energy between iron crystals and liquid oxide slag had been the same as in copper, there could have been no iron age for iron cannot be melted in primitive furnaces and consolidation by welding would have been impossible. The basic relation between technique and design is discussed at length. Thirteen different techniques used in making molds for Chinese bronzes are listed, each with some effect on the appearance, but the main quality of the bronzes arises from the fact that the decorative details were developed in the mold, not on a model. Worked metals demand a different quality of design from those made by casting, and objects forged integrally differ from those constructed by joining together pre-shaped parts of wire or sheet. The value of metallography in reconstructing ancient techniques is illustrated with a study of Cretan bronze armor made from sheet and wire. The use of etching to produce decorative patterns seems to have begun with carnelian beads in Harappa. lt was used on metal in China about 500 B. C. in a process involving mineralization in situ rather than complete removal of metal. It was used to bite designs on armor before its use in the graphic arts. The Japanese sword guard maker used etching to achieve very subtle surface textures based on the internal structure of his alloys, sometimes dendritic crystals, sometimes equiaxed grains but best of all in the twophase alloy of copper and silver, shibuichi. The Japanese sword is the best example of a satisfactory art form based on the inner nature of metal. The texture of the metal itself depends upon intricacies of forging, and the intricately-shaped interface between hard and soft metal follows a pattern of diffusion of carbon and heat under conditions only partially controlled by the smith. Though based upon the microstructure of materials, the paper suggests that form, in its broadest sense, arises in the mutual two-way interaction between parts and wholes, between imperfections in atomistic structures and historically-based larger ones, between human control and the nature of matter. Much of man's exploitation of the richness of materials has come about because he can see them at a scale where a new quality is emerging from the structural hierarchy of quantity .