Leather is a strong, flexible and durable material obtained from the tanning, or chemical treatment, of animal skins and hides to prevent decay. The most common leathers come from cattle, sheep, goats, equine animals, buffalo, pigs and hogs, and aquatic animals such as seals and alligators.
Leather can be used to make a variety of items, including clothing, footwear, handbags, furniture, tools and sports equipment, and lasts for decades. Leather making has been practiced for more than 7,000 years and the leading producers of leather today are China and India.
Critics of tanneries claim that they engage in unsustainable practices that pose health hazards to the people and the environment near them.
The leather manufacturing process is divided into three fundamental subprocesses: preparatory stages, tanning, and crusting. A further subprocess, finishing, can be added into the leather process sequence, but not all leathers receive finishing.
The preparatory stages are when the hide is prepared for tanning. Preparatory stages may include soaking, hair removal, liming, deliming, bating, bleaching, and pickling.
Tanning is a process that stabilizes the proteins, particularly collagen, of the raw hide to increase the thermal, chemical and microbiological stability of the hides and skins, 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.
Leather can be oiled to improve its water resistance. This currying process after tanning supplements the natural oils remaining in the leather itself, which can be washed out through repeated exposure to water. Frequent oiling of leather, with mink oil, neatsfoot oil, or a similar material keeps it supple and improves its lifespan dramatically.
Tanning processes largely differ in which chemicals are used in the tanning liquor. Some common types include:
In general, leather is produced in the following grades:
Today, most leather is made of cattle hides, which constitute about 65% of all leather produced. Other animals that are used include sheep (about 13%), goats (about 11%), and pigs (about 10%). Obtaining accurate figures from around the world is difficult, especially for areas where the skin may be eaten.Other animals mentioned below only constitute a fraction of a percent of total leather production.
Horse hides are used to make particularly durable leathers. Shell cordovan is a horse leather made not from the outer skin but from an under layer, found only in equine species, called the shell. It is prized for its mirror-like finish and anti-creasing properties.
Lamb and deerskin are used for soft leather in more expensive apparel. Deerskin is widely used in work gloves and indoor shoes.
Reptilian skins, such as alligator, crocodile, and snake, are noted for their distinct patterns that reflect the scales of their species. This has led to hunting and farming of these species in part for their skins. The Argentine black and white tegu is one of the most exploited reptile species in the world in the leather trade. However, it is not endangered and while monitored, trade is legal in most South American countries.
Kangaroo leather is used to make items that must be strong and flexible. It is the material most commonly used in bullwhips. Some motorcyclists favor kangaroo leather for motorcycle leathers because of its light weight and abrasion resistance.Kangaroo leather is also used for falconry jesses, soccer footwear, (e.g. Adidas Copa Mundial ) and boxing speed bags.
Although originally raised for their feathers in the 19th century, ostriches are now more popular for both meat and leather.Ostrich leather has a characteristic "goose bump" look because of the large follicles where the feathers grew. Different processes produce different finishes for many applications, including upholstery, footwear, automotive products, accessories, and clothing.
In Thailand, stingray leather is used in wallets and belts. Stingray leather is tough and durable. The leather is often dyed black and covered with tiny round bumps in the natural pattern of the back ridge of an animal. These bumps are then usually dyed white to highlight the decoration. Stingray rawhide is also used as grips on Chinese swords, Scottish basket hilted swords, and Japanese katanas. Stingray leather is also used for high abrasion areas in motorcycle racing leathers (especially in gloves, where its high abrasion resistance helps prevent wear through in the event of an accident).
For a given thickness, fish leather is typically much stronger due to its criss-crossed fibers.
Leather produces some environmental impact, most notably due to:
Estimates of the carbon footprint of bovine leather range from 65 to 150 kg of CO2 equivalent per square meter of production.
One ton of hide or skin generally produces 20 to 80 m3 of waste water, including chromium levels of 100–400 mg/L, sulfide levels of 200–800 mg/L, high levels of fat and other solid wastes, and notable pathogen contamination. Producers often add pesticides to protect hides during transport. With solid wastes representing up to 70% of the wet weight of the original hides, the tanning process represents a considerable strain on water treatment installations.
Leather biodegrades slowly—taking 25 to 40 years to decompose. [ failed verification ] However, vinyl and petrochemical-derived materials take 500 or more years to decompose.
Tanning is especially polluting in countries where environmental regulations are lax, such as in India, the world's third-largest producer and exporter of leather. To give an example of an efficient pollution prevention system, chromium loads per produced tonne are generally abated from 8 kg to 1.5 kg. VOC emissions are typically reduced from 30 kg/t to 2 kg/t in a properly managed facility. A review of the total pollution load decrease achievable according to the United Nations Industrial Development Organization posts precise data on the abatement achievable through industrially proven low-waste advanced methods, while noting, "even though the chrome pollution load can be decreased by 94% on introducing advanced technologies, the minimum residual load 0.15 kg/t raw hide can still cause difficulties when using landfills and composting sludge from wastewater treatment on account of the regulations currently in force in some countries."
In Kanpur, the self-proclaimed "Leather City of World"—with 10,000 tanneries as of 2011 and a city of three million on the banks of the Ganges—pollution levels were so high, that despite an industry crisis, the pollution control board decided to shut down 49 high-polluting tanneries out of 404 in July 2009.In 2003 for instance, the main tanneries' effluent disposal unit was dumping 22 tonnes of chromium-laden solid waste per day in the open.
In the Hazaribagh neighborhood of Dhaka in Bangladesh, chemicals from tanneries end up in Dhaka's main river. Besides the environmental damage, the health of both local factory workers and the end consumer is also negatively affected.After approximately 15 years of ignoring high court rulings, the government shut down more than 100 tanneries the weekend of 8 April 2017 in the neighborhood.
The higher cost associated with the treatment of effluents than to untreated effluent discharging leads to illegal dumping to save on costs. For instance, in Croatia in 2001, proper pollution abatement cost US$70–100 per ton of raw hides processed against $43/t for irresponsible behavior.In November 2009, one of Uganda's main leather making companies was caught directly dumping waste water into a wetland adjacent to Lake Victoria.
Enzymes like proteases, lipases, and amylases have an important role in the soaking, dehairing, degreasing, and bating operations of leather manufacturing. Proteases are the most commonly used enzymes in leather production. The enzyme must not damage or dissolve collagen or keratin, but should hydrolyze casein, elastin, albumin, globulin-like proteins, and nonstructural proteins that are not essential for leather making. This process is called bating.
Lipases are used in the degreasing operation to hydrolyze fat particles embedded in the skin.
Amylases are used to soften skin, to bring out the grain, and to impart strength and flexibility to the skin. These enzymes are rarely used.
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 humidities. Although it is chemically irreversible, treatments can add handling strength and prevent disintegration of red rotted leather.
Exposure to long periods of low relative humidities (below 40%) can cause leather to become desiccated, irreversibly changing the fibrous structure of the leather. Chemical damage can also occur from exposure to environmental factors, including ultraviolet light, ozone, acid from sulfurous and nitrous pollutants in the air, or through a chemical action following any treatment with tallow or oil compounds. Both oxidation and chemical damage occur faster at higher temperatures.
There are few methods to maintain and clean leather goods properly such as using damp cloth and avoid using a wet cloth or soaking the leather in water.Various treatments are available such as conditioners. Saddle soap is used for cleaning, conditioning, and softening leather. Leather shoes are widely conditioned with shoe polish.
Due to its excellent resistance to abrasion and wind, leather found a use in rugged occupations. The enduring image of a cowboy in leather chaps gave way to the leather-jacketed and leather-helmeted aviator. When motorcycles were invented, some riders took to wearing heavy leather jackets to protect from road rash and wind blast; some also wear chaps or full leather pants to protect the lower body.
Leather's flexibility allows it to be formed and shaped into balls and protective gear. Subsequently, many sports use equipment made with leather, such as baseball gloves and the ball used in cricket and gridiron football.
Leather fetishism is the name popularly used to describe a fetishistic attraction to people wearing leather, or in certain cases, to the garments themselves.
Many rock groups (particularly heavy metal and punk groups in the 1970s and 80s) are well known for wearing leather clothing. Extreme metal bands (especially black metal bands) and Goth rock groups have extensive black leather clothing. Leather has become less common in the punk community over the last three decades, as there is opposition to the use of leather from punks who support animal rights.
Many cars and trucks come with optional or standard leather or "leather faced" seating.
In countries with significant populations of individuals observing religions which place restrictions on material choices, vendors typically clarify the source of leather in their products. Such labeling helps facilitate religious observance, so, for example, a Muslim will not accidentally purchase pigskin or a Hindu can avoid cattleskin. Such taboos increase the demand for religiously neutral leathers such as ostrich and deer.
Judaism forbids the comfort of wearing leather shoes on Yom Kippur, Tisha B'Av, and during mourning.Also, see Teffilin and Torah Scroll.
Jainism prohibits the use of leather, since it is obtained by killing animals.
Many forms of artificial leather have been developed, usually involving polyurethane or vinyl coatings applied to a cloth backing. Many names and brands for such artificial leathers exist, including "pleather", a portmanteau of "plastic leather", and the brand name Naugahyde.
Another alternative is cultured leather which is lab-grown using cell-culture methods,mushroom-based materials and gelatin-based textile made by upcycling meat industry waste. Leather made of fungi or mushroom-based materials are completely biodegradable.
Tanning is the process of treating skins and hides of animals to produce leather. A tannery is the place where the skins are processed.
Shell cordovan or cordovan is a type of leather commonly used in high-end shoemaking. Cordovan is an equine leather made from the fibrous flat connective tissue beneath the hide on the rump of the horse. The leather derives its name from the city of Cordoba, Spain, where it was first produced by the Visigoths in the seventh century, and later also by the Moors. It is a difficult and expensive leather to make, and in the late 19th and early 20th century was mostly used for razor strops to sharpen razors in barber shops. More recently it has been increasingly used for shoes, wallets, and watch straps due to its aesthetic qualities and exceptional durability. It is also used in archery to protect the fingers. It is smooth and durable, ideal for a finger tab. Shell cordovan has a unique non-creasing characteristic. Because it is made of connective tissue, it is smooth and lacks the pebbled effect of leather derived from animal skin.
Industrial wastewater treatment describes the processes used for treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater may be reused or released to a sanitary sewer or to a surface water in the environment. Some industrial facilities generate wastewater that can be treated in sewage treatment plants. Most industrial processes, such as petroleum refineries, chemical and petrochemical plants have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with the regulations regarding disposal of wastewaters into sewers or into rivers, lakes or oceans. This applies to industries that generate wastewater with high concentrations of organic matter, toxic pollutants or nutrients such as ammonia. Some industries install a pre-treatment system to remove some pollutants, and then discharge the partially treated wastewater to the municipal sewer system.
Artificial leather, also called synthetic leather, is a material intended to substitute for leather in upholstery, clothing, footwear, and other uses where a leather-like finish is desired but the actual material is cost prohibitive or unsuitable, or for ethical concerns. Artificial leather is known under many names, including leatherette, imitation leather, faux leather, vegan leather, PU leather, and pleather.
Nubuck is top-grain leather that has been sanded or buffed on the grain side, or outside, to give a slight nap of short protein fibers, producing a velvet-like surface. It is resistant to wear, and may be white or coloured.
Ostrich leather is the result of tanning skins taken from African ostriches farmed for their feathers, skin and meat. The leather is distinctive for its pattern of bumps or vacant quill follicles, ranged across a smooth field in varying densities. It requires an intricate, specialised and expensive production process making its aesthetic value costly.
Morocco leather is a vegetable-tanned leather known for its softness, pliability, and ability to take color. It has been widely used in the manufacture of gloves and the uppers of ladies' shoes and men's low cut shoes, but is commonly associated with wallets, linings for fine luggage, and bookbindings.
Title 40 is a part of the United States Code of Federal Regulations. Title 40 arranges mainly environmental regulations that were promulgated by the US Environmental Protection Agency (EPA), based on the provisions of United States laws. Parts of the regulation may be updated annually on July 1.
This article discusses topics related to the environment of Pakistan.
The leather manufacturing process is divided into three sub-processes: preparatory stages, tanning and crusting. All true leathers will undergo these sub-processes. A further sub-process, surface coating may be added into the sequence. The list of operations that leathers undergo vary with the type of leather.
S.B. Foot Tanning Company is a leather production facility located in Red Wing, Minnesota. It processes leather for use in the crafting of shoes, boots, belts, and leather accessories. In 2010, the factory processed nearly 6 million linear feet of hides. S.B. Foot Tanning Company is a wholly owned subsidiary of Red Wing Shoes Company, Inc. and is the principal supplier of leather to their shoe manufacturing plants. The company also supplies over 1.5 million linear feet of leather for use in the production of military footwear per year, extending a tradition that began with World War I, when the tannery supplied boot leathers for the construction of soldier boots.
The Tannery is a historic tannery building constructed by the colonial Moravians in Bethlehem, Northampton County, Pennsylvania. It is a limestone building built in 1761, and is part of the Bethlehem Colonial Industrial Quarter.
Humanity has used animal hides since the Paleolithic, for clothing as well as mobile shelters such as tipis and wigwams, and household items. Since ancient times, hides have also been used as a writing medium, in the form of parchment.
The introduction of Polypropylene drums permitted the routine commercial use of a range of highly corrosive chemicals in the tanning industry, for processes such as depilation and bleaching. In spite of the cheapness of the processes, the required chemicals are too aggressive for most practical choices of metal drums.
Russia leather is a particular form of bark-tanned cow leather. It is distinguished from other types of leather by a processing step that takes place after tanning, where birch oil is worked into the rear face of the leather. This produces a leather that is hard-wearing, flexible and resistant to water. The oil impregnation also deters insect damage. This leather was a major export good from Russia in the 17th and 18th centuries because of its high quality, its usefulness for a range of purposes, and the difficulty of replicating its manufacture elsewhere. It was an important item of trade for the Muscovy Company. In German-speaking countries, this leather was also known by the name Juchten or Juften.
[Islamabad]] has many environmental issues, severely affecting its biophysical environment as well as human health. The industrialization as well as lax environmental oversight have contributed to the problems. The various forms of pollution have increased as Karachi which has caused widespread environmental and health problems. Air pollution, lack of proper waste management infrastructure and degradation of water bodies are the major environmental issues in Karachi.
The conservation and restoration of leather objects is the process of determining the causes of deterioration, followed by deciding the best course of action for preserving the leather objects for the future.
Chouara Tannery is one of the three tanneries in the city of Fez, Morocco. It is the largest tannery in the city and one of the oldest. It is located in the Fes el Bali, the oldest medina quarter of the city, near the Saffarin Madrasa along the Oued Fes. Since the inception of the city, the tanning industry has been continually operating in the same fashion as it did in the early centuries. Today, the tanning industry in the city is considered one of the main tourist attractions. The tanneries are packed with the round stone vessels filled with dye or white liquids for softening the hides. The leather goods produced in the tanneries are exported around the world.
Leather is created when an animal skin or hide is chemically treated in a process called tanning to preserve them for long term use as material for clothing, handbags, footwear, furniture, sports equipment and tools. Alligator leather is also commonly used to create similar items as mentioned above.
Carl Erengisle Hyltén-Cavallius, born 19 February 1817 in Vislanda; died 29 October 1853 in Gothenburg, was a Swedish pharmacist and chemist; he invented the now dominating technology of tanning by using chromium salts.