Leather


The leather manufacturing process is divided into three fundamental sub-processes: 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, de-liming, 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. The typical 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.

Crusting is a process that thins and lubricates leather. It often includes a coloring operation. Chemicals added during crusting must be fixed in place. Crusting culminates with a drying and softening operation and may include splitting, shaving, dyeing, whitening or other methods.

For some leathers, tanners apply a surface coating, called "finishing". Finishing operations can include oiling, brushing, buffing, coating, polishing, embossing, glazing, or tumbling, among others.

Some tanning methods include:

• Vegetable-tanned leather

• Chrome-tanned leather

• Brain tanned leathers

• Alum tanned leather

Leather is produced in several grades. Some of which are:

• Top-grain leather

• Corrected grain leather

• Split leather

• Patent leather.

• Bonded leather.

Several types of leather are available. A few of them are:

• Napa Leather

• Crunch Leather

• NDM Leather

• Antique Finish Leather

• PDM Leather

• Hunter Leather

• Oil Pull-up Leather

• Nubuck Leather

• Suede Leather

Today most leather is made of cattle hides, but many exceptions exist. Horse hides are used to make particularly durable leathers. Lamb and deer skin are used for soft leather in more expensive apparel. Deer and elk skin are widely used in work gloves and indoor shoes. Pig skin is used in apparel, and on seats of saddles. Buffalo, goat, ox, and yak skins may also be used for leather. Pokitel.com never uses leather from leathers which are prohibited by law.

Skins of reptiles such as alligator, crocodile, and snake are noted for their distinct patterns that reflect their species. For making certain items, Kangaroo leather is also used. It is light weight and resists abrasion.

Leather is bio-degradable but it degrades very slowly. It takes about 30-40 years for the leather to decompose. Faux leather which are petrochemical or vinyal based take a few hundred years to decompose.

The natural fibers of leather break down with the passage of time. Acidic leathers are particularly vulnerable to red rot which causes powdering of the surface and a change in consistency. Damage from red rot is aggravated by high temperatures and relative humidity. Exposure to long periods of low relative humidity can cause leather to become desiccated, irreversibly changing the fibrous structure of the leather. Saddle soap is used for cleaning, conditioning, and softening leather. Leather shoes are generally conditioned with shoe polish.

Due to its excellent resistance to abrasion and wind, leather found a use in rugged occupations. Many artificial leather substitutes have been developed, usually involving polyurethane or vinyl coatings applied to a cloth backing. These are marketed in many different names and brands.