Primitive man covered himself with the skins of animals he killed.

They had three major defects: 
1) they were damp,
2) they would putrefy,
3) they lost their flexibility and softness upon drying. (They dried the skins to stop putrefaction).

The making of leather is one of the oldest crafts (>3000years). Hides and skins are turned into leather by tanning. 

Tanning causes following changes:
1) putrefaction does not take place,
2) the skin remains flexible on drying

Hides and skins (hides- of larger animals; skins- of smaller animals) become durable and capable of being used for a wide range of purposes. Many uses of leather demand different properties. These are obtained by choice of raw material and variation of processes.  Skins of mammals, ox, cow, calf, buffalo, sheep, goat, pig and horse form the main raw material but kangaroo and camel may also be used. Marine animals (whales, seals, sharks and bony fish) and reptiles (alligators, snakes, lizards) are processed as well.

The technology of leather making is in its broadest sense, a series of operations which aim at isolating collagen by removing noncollagenous components of skin and then at making it resistant to physical, chemical and biological factors. First part is carried in tannery beam house, the second in tanning and finishing departments.