Leather is not simply the skin of dead animal ; it is a material made by tanner. Once an animal has been killed for food , the skin becomes a waste product, which could be thrown away and allowed to decompose. Instead, it is transformed into a flexible , tactile material with a multitude of uses.Leatherworkers have long been aware of the special nature of leather, but it was not until the coming of microscopy that the underlying structure of leather was discovered and its secret revealed. From the leatherworkers point of view, the most important part of an animal skin is the corium. The corium consists mainly of the protein collagen, the fibres of which are grouped together into "bundels" it is the three-dimensional interweaving of these bundles of fibres throughout the thickness of the skin that gives leather its unique structure and adaptability. The largest bundles are found in the middle of the corium , and the fibres become finer and more closely woven towards the surface of the grain.It is the organization of the bundles of fibres and their ability to move in response to stresses and strains that give leather its characteristics - its flexibility , strength , elasticity, malleability and ability to breathe. By studying the structure of the fibres , leather chemists have discovered how to affect the angle at which the fibres are woven and so to produce a range of leathers suited to a variety of specific needs.
TANNING
Tanning can be described as the production from animal skin of a chemically and biologically stable material by a process that leaves the original fibre structure more or less intact. It is a process that transforms animal skin , which is a highly complex product of nature , into a sophisticated material with countless uses.Before tanning can begin , hides and skins have to be modified by a series of pre-tanning operations. These includes the removal of the hair and epidermis from the top. a process known as liming , and the removal of the layer of flesh from underneath , which is known as fleshing. it is the middle layer , the corium , that is left and that becomes leather.
Tanning methods using smoke , animal ,and fish oils, and alum salts (known as tawing), are still practised throughout the world on a small scale. The two main methods of tanning in use today , however , are chrome tanning and vegetable tanning.
