Leather is a durable and flexible material created by tanning animal rawhides, mostly cattle hide. It can be produced at manufacturing scales ranging from cottage industry to heavy industry.
Leather is used to make various goods, including clothing (especially footwear), in bookbinding, and as a furniture covering. It is produced in a wide variety of types and styles, decorated by a wide range of techniques. The earliest record of leather artefacts date back to 1300 BC and
The leather manufacturing process is divided into three fundamental subprocesses: preparatory stages, tanning, and crusting. A further subprocess, surface coating, can be added into the leather process sequence, but not all leathers receive surface treatment.
The preparatory stages are when the hide is prepared for tanning. Preparatory stages may include: liming, deliming, hair removal, degreasing, bleaching, and pickling.
Tanning is a process that stabilizes the proteins of the raw hide so it does not putrefy, making it suitable for a wide variety of end applications. The principal difference between raw and tanned hides is that raw hides dry out to form a hard, inflexible material that, when rewetted, will putrefy, while tanned material dries to a flexible form that does not become putrid when rewetted.
Many tanning methods and materials exist although the traditional method used tannin, an acidic substance derived from oak trees. The process sees tanners load the hides into a drum and immerse them in a tank that contains the tanning "liquor". The hides soak while the drum slowly rotates about its axis, and the tanning liquor slowly penetrates through the full thickness of the hide. Once the process achieves even penetration, workers slowly raise the liquor's pH in a process called basification, which fixes the tanning material to the leather. The more tanning material fixed, the higher the leather's hydrothermal stability and shrinkage temperature resistance. Chrome-tanned leather pH is typically between pH 3.8 and 4.2.