Leather and its process

Leather is a strong, flexible and durable material obtained by tanning or chemically treating animal hides and hides to prevent decay. The most common hides come from cattle,sheep,goats,equines,buffaloes,pigs and wild boars,as well as aquatic animals such as seals and alligators.Leather is used to make a variety of items including clothing,footwear,handbags,furniture,tools and sports equipment and lasts for decades.The tanning industry has a history of over 7,000 years and today the major leather producing countries are China and India.Critics of tanneries claim they engage in unsustainable practices that pose health hazards to nearby people and the environment.

Production processes 

The leather manufacturing process is divided into three basic sub-processes:preparation phase,tanning and crusting.A further sub-process,finishing,can be added to the leather crafting sequence,but not all leathers receive finishing.The prep phase is the stage where the hide is ready for tanning.Preparation stages may include soaking,dehairing,liming,deliming,softening,bleaching and pickling.Tanning is a process of stabilizing hide and hide proteins, especially collagen,which increases the thermal, chemical and microbiological stability of hides and hides,making them suitable for various end-use applications.The key difference between rawhide and tanned leather is that rawhide dries to a hard, inflexible material that rots when rewetted whereas tanned material dries to a soft form that does not rewet rot.Many tanning methods and materials exist.In a typical process,the tanner loads the hides into drums and dips them into vats containing tanning "liquid".The hide is soaked while the drum rotates slowly around its axis, allowing the tanning solution to slowly penetrate the entire thickness of the hide.Once the process has achieved uniform penetration, workers slowly raise the pH of the liquid in a process called alkalization, which fixes the tanning material on the hide.The more fixed tanning material, the higher the hydrothermal stability and shrinkage resistance of the leather.Scabbing is a process that thins and lubricates the leather.It usually includes shading operations.Chemicals added during scabbing must be fixed in place. Scabs end with drying and softening procedures,which may include splitting,shaving,staining, whitening,or other methods.With some leathers, tanners apply a surface coating called a 'finish'.Finishing operations may include oiling,brushing,buffing,coating,buffing,embossing,varnishing or tumbling, among others.Leather can be oiled to increase its water resistance.This curry treatment after tanning replenishes the natural oils left on the leather itself,which can be washed away with repeated exposure to water.Regularly oiling the leather with mink oil, cowsfoot oil or a similar material will keep it supple and extend its life considerably.

Tanning method

Tanning processes vary widely in the chemicals used in the tanning liquor. Some common types include:Vegetable tanned leather is      tanned using tannins extracted from plant matter, such as bark prepared in bark factories.This is the oldest known method.It is a soft light brown,the exact shade depending on the mix of materials and the color of your skin.Tan gets its name from the appearance of undyed, vegetable-tanned leather.Vegetable tanned leather is unstable in water; it discolours easily,and if soaked and then allowed to dry, it shrinks and hardens, a characteristic of vegetable tanned leather utilized in traditional shoemaking.In hot water,it shrinks dramatically and partially coagulates,becoming hard and eventually brittle.An example of this is boiled leather, where leather is hardened by immersing it in boiling water,wax,or a similar substance.Occasionally used as armor when hardened historically, also used to bind books.Chrome tanned leather is tanned using chromium sulfate and other chromium salts.Undyed leather has a pale blue color and is also known as "wet blue".Chrome tanning usually takes about a day to complete and is therefore best suited for large-scale industrial use.This is the most common method in modern use.It is softer and more flexible than vegetable tanned leather and will not discolor or deform in water as drastically as vegetable tanned leather.However, this tanning method has environmental concerns because chromium is a heavy metal; while the trivalent chromium used for tanning is harmless, other by-products may contain toxic variants.The method was developed in the second half of the 19th century when tanneries wanted to find ways to speed up the process and make the leather more water resistant.