Fish scale the surface, interacting only with the riblet tips, not causing any high-veloctiy flow in the valleys. Since this high velocity flow now only interacts with the riblet-tip, which is a very small surface area, the momentum transfer which causes drag is now much lower than before, thereby effectively reducing drag. Also, this reduces the cross-stream velocity fluctuations, which aids in momentum transfer too. The rough, sandpaper-like texture of shark and ray skin, coupled with its toughness, has led it to be valued as a source of rawhide leather, called shagreen. One of the many historical applications of shark shagreen was
Santiniketan Leather Goods cotton pad or a glass, which has a smooth surface, is used to make the grains of the leather shine. The raw materials used in making these goods are classified according to the grain quality and smoothness as E.I. Tanned leathers of sheepskin or goatskin that are dyed with vegetable colours. Three leather types are defined: "Paper" which has a coarse grain and spots is the skin of larger goats or sheep, and "Bind" and "Kid" which are both derived from smaller animals and are of superior quality. Other materials used to make the final product include paper board of