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Leather is a strong, flexible and durable material obtained from the
tanning Tanning may refer to: *Tanning (leather), treating animal skins to produce leather *Sun tanning, using the sun to darken pale skin **Indoor tanning, the use of artificial light in place of the sun **Sunless tanning, application of a stain or dye to ...
, or chemical treatment, of animal skins and hides to prevent decay. The most common leathers come from
cattle Cattle, taurine cattle, Eurasian cattle, or European cattle (''Bos taurus'' or ''Bos primigenius taurus'') are large domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a signific ...

cattle
,
sheep Sheep (''Ovis aries'') are quadruped The zebra is a quadruped. Quadrupedalism is a form of terrestrial locomotion where a tetrapod Tetrapods (; from Greek 'four' and 'foot') are four-limbed animals constituting the superclass Tetrapo ...

sheep
, goats,
equine Equinae is a subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family (biology), family but more inclusive than genus. Standard nomenclature rules end subfamily bo ...
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. Animal rights groups claim that modern commercial leather making and the consumption of its products is unethically killing animals. According to the life-cycle assessment (LCA) report for the United Nations Industrial Development Organization, 99% of the raw hides and skins used in the production of leather derive from animals raised for meat and/or dairy production. Critics of
tanneries Tanning may refer to: *Tanning (leather), treating animal skins to produce leather *Sun tanning, using the sun to darken pale skin **Indoor tanning, the use of artificial light in place of the sun **Sunless tanning, application of a stain or dye to ...
claim that they engage in unsustainable practices that pose health hazards to the people and the environment near them. The processing stages of tanneries use thousands of liters of water for one hide or animal skin and release toxic liquid waste into the environment that can cause soil depletion and health issues related to the human skin, respiratory system and more. However, advancements have been made in the amount and treatment of water used by tanneries to reduce impact.


Production processes

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,
delimingThe deliming operation in leather Leather is a durable and flexible material created by tanning animal rawhide and skins. The most common raw material is cattle hide. It can be produced at manufacturing scales ranging from artisan to modern ...
, bating,
bleaching Bleach is the generic name for any chemical product which is used industrially and domestically to remove color from a fabric or fiber or to clean or to remove stains in a process called bleaching. It often refers, specifically, to a dilute s ...
, and
pickling Pickling is the process of preserving or extending the shelf life of food Food is any substance consumed to provide Nutrient, nutritional support for an organism. Food is usually of plant, animal or Fungus, fungal origin, and contains essen ...
.
Tanning Tanning may refer to: *Tanning (leather), treating animal skins to produce leather *Sun tanning, using the sun to darken pale skin **Indoor tanning, the use of artificial light in place of the sun **Sunless tanning, application of a stain or dye to ...
is a process that stabilizes the
protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , and from one location to another. Proteins differ from one another primarily ...

protein
s, particularly
collagen Collagen () is the main structural in the found in the body's various s. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole-body protein content. Collagen consists of ...

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 Dyeing is the application of dyes 300px, Yarn drying after being dyed in the early American tradition, at living_history_museum.html"_;"title="Conner_Prairie_living_history_museum">Conner_Prairie_living_history_museum. A_dye_is_a_ Conner_Pr ...

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 In mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It ...
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 Mink oil is an oil used in medical and cosmetic products. It is obtained by the rendering of mink Mink are dark-colored, semiaquatic, carnivorous mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate anim ...
,
neatsfoot oil upNeatsfoot oil Neatsfoot oil is a yellow oil rendering (industrial), rendered and purified from the shin bones and feet (but not the hoof, hooves) of cattle. "Neat" in the oil's name comes from an Old English word for cattle. Neatsfoot oil is use ...
, or a similar material keeps it supple and improves its lifespan dramatically.


Tanning methods

Tanning processes largely differ in which chemicals are used in the tanning liquor. Some common types include: * is tanned using
tannin Tannins (or tannoids) are a class of , ic s that bind to and s and various other organic compounds including s and s. The term ''tannin'' (from ''tanner'', from ''tannāre'', from ''tannum'', ) refers to the use of oak and other bark ...
s extracted from
vegetable matter Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is applied to plants collectively to refer to all edible plant matter, including the flowers A flower ...
, such as tree
bark Bark may refer to: * Bark (botany), an outer layer of a woody plant * Bark (sound), a vocalization of some animals Places * Bark, Germany * Bark, Warmian-Masurian Voivodeship, Poland Arts, entertainment, and media * ''Bark'' (Jefferson Airp ...
prepared in
bark mill Bark mills, also known as Catskill’s mills, were water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the mai ...
s. It is the oldest known method. It is supple and light brown in color, with the exact shade depending on the mix of materials and the color of the skin. The color tan derives its name from the appearance of undyed vegetable-tanned leather. Vegetable-tanned leather is not stable in water; it tends to discolor, and if left to soak and then dry, it shrinks and becomes harder, a feature of vegetable-tanned leather that is exploited in traditional shoemaking. In hot water, it shrinks drastically and partly congeals, becoming rigid and eventually brittle.
Boiled leather Boiled leather, often referred to by its French translation, cuir bouilli (), was a historical material for various uses common in the Middle Ages and Early Modern Period. It was leather that had been treated so that it became tough and rigid, as w ...
is an example of this, where the leather has been hardened by being immersed in boiling water, or in
wax Waxes are a diverse class of organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, ...
or similar substances. Historically, it was occasionally used as
armor Armour (British English British English (BrE) is the standard dialect of the English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, whi ...

armor
after hardening, and it has also been used for
book binding Bookbinding is the process of physically assembling a book A book is a medium for recording information Information can be thought of as the resolution of uncertainty; it answers the question of "What an entity is" and thus defines ...
. * Chrome-tanned leather is tanned using chromium sulfate and other
chromium Chromium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science tha ...

chromium
salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure fo ...
s. It is also known as "wet blue" for the pale blue color of the undyed leather. The chrome tanning method usually takes approximately one day to complete, making it best suited for large-scale industrial use. This is the most common method in modern use. It is more supple and pliable than vegetable-tanned leather and does not discolor or lose shape as drastically in water as vegetable-tanned. However, there are environmental concerns with this tanning method, as chromium is a heavy metal; while the trivalent chromium used for tanning is harmless, other byproducts can contain toxic variants. The method was developed in the latter half of the 19th century as tanneries wanted to find ways to speed up the process and to make leather more waterproof. * Aldehyde-tanned leather is tanned using
glutaraldehyde Glutaraldehyde, sold under the brandname Cidex and Glutaral among others, is a disinfectant, medication, preservative, and fixative. As a disinfectant, it is used to sterilize surgical instruments and other areas of hospitals. As a medication, ...
or
oxazolidine An oxazolidine is a five-membered ring compound consisting of three carbon Carbon (from la, carbo "coal") is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elem ...

oxazolidine
compounds. It is referred to as "wet white" due to its pale cream color. It is the main type of "chrome-free" leather, often seen in shoes for infants and automobiles.
Formaldehyde Formaldehyde ( , also ) (systematic nameA systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance A chemical substance is a form of matter In classical physics and general chemist ...
has been used for tanning in the past; it is being phased out due to danger to workers and sensitivity of many people to formaldehyde. **
Chamois leather Chamois leather () is a type of porous leather, traditionally the skin of the chamois (''Rupicapra rupicapra''), a type of European mountain goat, but today made almost exclusively from the flesh split of a sheepskin. Uses The leather is favo ...
is a form of aldehyde tanning that produces a porous and highly water-absorbent leather. Chamois leather is made using marine oils (traditionally cod oil) that oxidize to produce the aldehydes that tan the leather. * Brain tanned leathers are made by a labor-intensive process that uses emulsified oils, often those of animal brains such as deer, cattle, and buffalo. They are known for their exceptional softness and washability. * Alum leather is transformed using
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
salts mixed with a variety of binders and
protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , and from one location to another. Proteins differ from one another primarily ...

protein
sources, such as flour and egg yolk. Alum leather is not actually tanned; rather the process is called "tawing", and the resulting material reverts to rawhide if soaked in water long enough to remove the alum salts.


Grades

In general, leather is produced in the following grades: * Top-grain leather includes the outer layer of the hide, known as the grain, which features finer, more densely packed fibers, resulting in strength and durability. Depending on thickness, it may also contain some of the more fibrous under layer, known as the corium. Types of top-grain leather include: **Full-grain leather contains the entire grain layer, without any removal of the surface. Rather than wearing out, it develops a
patina Patina (or ) is a thin layer that variously forms on the surface of , , and similar ( produced by oxidation or other chemical processes), or certain s, and wooden (sheen produced by age, wear, and polishing), or any similar acquired change ...

patina
during its useful lifetime. It is usually considered the highest quality leather. Furniture and footwear are often made from full-grain leather. Full-grain leather is typically finished with a soluble
aniline Aniline is an organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, and sy ...
dye.
Russia leatherRussia 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 (leather), tanning, where birch oil is worked into the rear face of the leather. This ...
is a form of full-grain leather. ** Corrected grain leather has the surface subjected to finishing treatments to create a more uniform appearance. This usually involves buffing or sanding away flaws in the grain, then dyeing and embossing the surface. **
Nubuck Nubuck (pronounced ) is top-grain leather Leather is a strong, flexible and durable material obtained from the tanning Tanning may refer to: *Tanning (leather), treating animal skins to produce leather *Sun tanning, using the sun to darken p ...
is top-grain leather that has been sanded or buffed on the grain side to give a slight nap of short protein fibers, producing a velvet-like surface. * Split leather is created from the corium left once the top-grain has been separated from the hide, known as the drop split. In thicker hides, the drop split can be further split into a middle split and a flesh split. **
Bicast leather Bicast leather (also spelled as bi-cast leather or bycast leather) is a material made with a split leather backing covered with an embossed layer of polyurethane or Polyvinyl chloride, vinyl. Bicast leather was originally made for the apparel indust ...
is split leather that has a polyurethane or vinyl layer applied to the surface and embossed to give it the appearance of a grain. It is slightly stiffer than top-grain leather but has a more consistent texture. **
Patent leather Patent leather is a type of coated leather Leather is a durable and flexible material created by tanning animal rawhide and skins. The most common raw material is cattle hide. It can be produced at manufacturing scales ranging from arti ...
is leather that has been given a high-gloss finish by the addition of a coating. Dating to the late 1700s, it became widely popular after inventor
Seth Boyden 300px, Seth Boyden Seth Boyden (November 17, 1788 – March 31, 1870) was an American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the United States The United St ...
developed the first mass-production process, using a linseed-oil-based lacquer, in 1818. Modern versions are usually a form of bicast leather. **
Suede Suede (pronounced ()) is a type of leather with a fuzzy, napped finish, commonly used for jackets, shoes, Textile, fabrics, Handbag, purses, furniture, and other items. The term comes from the French , which literally means "gloves from Sweden". ...
is made from the underside of a split to create a soft, napped finish. It is often made from younger or smaller animals, as the skins of adults often result in a coarse, shaggy nap. *
Bonded leather Bonded leather, also called reconstituted leather or blended leather, is a term used for a manufactured upholstery material which contains animal hide. It is made as a layered structure of a fiber or paper backer covered with a layer of shredded le ...

Bonded leather
, also called ''reconstituted leather'', is a material that uses leather scraps that are shredded and bonded together with polyurethane or
latex Latex is a stable dispersion (emulsion An emulsion is a mixture of two or more liquids that are normally Miscibility, immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class o ...

latex
onto a fiber mesh. The amount of leather fibers in the mix varies from 10% to 90%, affecting the properties of the product.


From other animals

Today, most leather is made of
cattle Cattle, taurine cattle, Eurasian cattle, or European cattle (''Bos taurus'' or ''Bos primigenius taurus'') are large domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a signific ...

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 Image:Wingoxford.jpg, 225px, Shell cordovan oxford Brogue shoe, Brogue Shell cordovan or cordovan is a type of leather commonly used in Luxury goods, high-end shoemaking. Cordovan is an equine leather made from the fibrous flat connective tissue (o ...
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 An alligator is a crocodilia Crocodilia (or Crocodylia, both ) is an Order (biology), order of mostly large, predatory, List of semiaquatic tetrapods, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago ...
, crocodile, and
snake Snakes are elongated, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Many species of snakes ...
, 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 Kangaroo leather is a strong light weight leather derived from the hide of the kangaroo. Kangaroos Kangaroo industry, are harvested. Both the Kangaroo meat, meat and the hides are sold. Although most species of Macropodidae, macropod are protecte ...
is used to make items that must be strong and flexible. It is the material most commonly used in
bullwhip A bullwhip is a single-tailed whip (implement), whip, usually made of braided leather, designed as a tool for working with livestock. Bullwhips are pastoral tools, traditionally used to control livestock in open country. A bullwhip's length, fl ...

bullwhip
s. Some
motorcyclists Motorcycling is riding a motorcycle A motorcycle, often called a motorbike, bike, or cycle, is a two- or three-wheeled motor vehicle. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commutin ...

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, and boxing speed bags. Although originally raised for their feathers in the 19th century,
ostrich ''Struthio'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a ...

ostrich
es 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 Thailand ( th, ประเทศไทย), historically known as Siam, () officially the Kingdom of Thailand, is a country in Southeast Asia. It is located at the centre of the Mainland Southeast Asia, Indochinese Peninsula, spanning , wi ...

Thailand
,
stingray Stingrays are a group of sea rays, which are cartilaginous fish Chondrichthyes (; from Greek χονδρ- 'cartilage', ἰχθύς 'fish') is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartil ...

stingray
leather is used in
wallets and ATM card, cards, and a window to display an identification card A wallet is a small, flat case or pouch that can be used to carry such small personal items as paper currency, credit cards, and identification documents (driver's license, iden ...
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
katana A is a Japanese sword A is one of several types of traditionally made sword A sword is an edged and bladed weapons, edged, bladed weapon intended for manual cutting or thrusting. Its blade, longer than a knife or dagger, is attached t ...

katana
s. 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.


Environmental impact

Leather produces some environmental impact, most notably due to: * The carbon footprint of cattle rearing (see
environmental impact of meat production The environmental impact of meat production varies because of the wide variety of agricultural Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary hu ...
) * Use of chemicals in the tanning process (e.g.,
chromium Chromium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science tha ...

chromium
, , nonyl phenol ethoxylate soaps,
pentachlorophenol Pentachlorophenol (PCP) is an Organochloride, organochlorine compound used as a pesticide and a disinfectant. First produced in the 1930s, it is marketed under many trade names. It can be found as pure PCP, or as the sodium salt of PCP, the latte ...

pentachlorophenol
and
solvent A solvent (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

solvent
s) * Air pollution due to the transformation process (
hydrogen sulfide Hydrogen sulfide is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havi ...

hydrogen sulfide
is formed during mixing with acids and
ammonia Ammonia is a compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fort ...

ammonia
liberated during deliming, solvent vapors)


Carbon footprint

Estimates of the
carbon footprint A carbon footprint is the total greenhouse gas (GHG) emissions caused by an individual, event, organization, service, place or product, expressed as carbon dioxide equivalent. Greenhouse gases, including the carbon-containing gases carbon dio ...

carbon footprint
of bovine leather range from 65 to 150 kg of CO2 equivalent per square meter of production.


Water footprint

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.


Disposal

Leather biodegrades slowly—taking 25 to 40 years to
decompose Decomposition is the process by which dead organic substance , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds com ...

decompose
. However, vinyl and petrochemical-derived materials take 500 or more years to decompose.


Chemical waste disposal

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 VOC, VoC or voc may refer to: Science and technology * Open-circuit voltage (VOC), the voltage between two terminals when there is no external load connected * Variant of concern, a category used during the assessment of a new variant of a virus * ...

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 The United Nations Industrial Development Organization (UNIDO) (French/Spanish acronym: ONUDI) is a specialized agency United Nations Specialized Agencies are autonomous organizations working with the United Nations The United Nation ...
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 Kanpur ( ), is a metropolitan city in the background A metropolis () is a large city or conurbation which is a significant economic, political, and cultural center for a country or region, and an important hub for regional or internatio ...

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 The Ganges ( ) (in India: Ganga ( ); in Bangladesh: Padma River, Padma ( )). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international river to which India, Bangladesh, Nepal and China are the riparian ...

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 Bangladesh (, bn, বাংলাদেশ, ), officially the People's Republic of Bangladesh, is a country in South Asia South Asia is the southern region of Asia, which is defined in both geography, geographical and culture, ethno-c ...

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 , image_flag = Flag of Croatia.svg , image_coat = Coat of arms of Croatia.svg , anthem = "Lijepa naša domovino ''Lijepa naša domovino'' (; ) is the national anthem A national anthem is a song that ...

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 Lake Victoria ( luo, Nam Lolwe; lg, 'Nnalubaale; rw, Nyanza; also ''Ukerewe'') is one of the African Great Lakes. Though having multiple local language names, the lake was renamed after Queen Victoria by the explorer John Hanning Speke, the ...

Lake Victoria
.


Role of enzymes

Enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

Enzyme
s like
protease A protease (also called a peptidase or proteinase) is an enzyme Enzymes () are s that act as s (biocatalysts). Catalysts accelerate . The molecules upon which enzymes may act are called , and the enzyme converts the substrates into differe ...

protease
s,
lipase A lipase (, ) is any enzyme Enzymes () are s that act as s (biocatalysts). Catalysts accelerate . The molecules upon which enzymes may act are called , and the enzyme converts the substrates into different molecules known as . Almost all ...
s, and
amylase An amylase () is an enzyme Enzymes () are protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , and from one lo ...
s 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 Collagen () is the main structural in the found in the body's various s. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole-body protein content. Collagen consists of ...

collagen
or
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin Alpha-keratin, or α-keratin, is a type of keratin Keratin () is one of a family of fibrous structural proteins known as Scleroprot ...

keratin
, but should hydrolyze
casein Casein ( , from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman ...

casein
,
elastin Elastin is a key protein of the extracellular matrix. It is highly Elasticity (physics), elastic and present in connective tissue allowing many tissues in the body to resume their shape after stretching or contracting. Elastin helps skin to return ...
,
albumin Albumin is a family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subje ...
,
globulin The globulins are a family of globular protein 300px, 3-dimensional structure of hemoglobin, a globular protein. Globular proteins or spheroproteins are spherical ("globe-like") protein Proteins are large biomolecules or macromolecules that ...
-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.


Preservation and conditioning

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. 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 Shoe polish (or boot polish) is a waxy , , or that is used to polish, , and s or s to extend the 's life and restore its appearance. Shoe polishes are distinguished by their textures, which range from liquids to hard waxes. Solvent, waxes, a ...

shoe polish
.


In modern culture

Due to its excellent resistance to abrasion and wind, leather found a use in rugged occupations. The enduring image of a
cowboy A cowboy is an animal herder A herder is a pastoral A pastoral lifestyle is that of shepherds herd A herd is a social group of certain animals of the same species, either wildness, wild or Domestication, domestic. The form of ...

cowboy
in leather
chaps The Clearing House Automated Payment System (CHAPS) is real-time gross settlement Real-time gross settlement (RTGS) systems are specialist Electronic funds transfer, funds transfer systems where the transfer of money or securities takes place from ...

chaps
gave way to the leather-jacketed and leather-helmeted
aviator An aircraft pilot or aviator is a person who controls the flight of an aircraft An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using eit ...
. When
motorcycle A motorcycle, often called a motorbike, bike, cycle, or (if three-wheeled) trike, is a two- or three-wheeled motor vehicle Electric bicycles parked in Yangzhou's main street, Wenchang Lu. They are a very common way of transport in this city ...

motorcycle
s were invented, some riders took to wearing heavy leather
jackets A jacket is a garment for the upper body, usually extending below the hips. A jacket typically has sleeves, and fastens in the front or slightly on the side. A jacket is generally lighter, tighter-fitting, and less insulating than a coat (clothi ...

jackets
to protect from
road rash ''Road Rash'' is a motorcycle-racing video game series by Electronic Arts in which the player participates in violent, illegal street races. The series started on the Sega Genesis, Sega Genesis/Mega Drive and was released on various other systems ...
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 from leather, such as
baseball glove during the 1954 World Series. A baseball glove or mitt is a large leather glove worn by baseball Baseball is a bat-and-ball games, bat-and-ball game played between two opposing teams who take turns batting (baseball), batting and fiel ...

baseball glove
s and the
ball A ball is a round object (usually spherical of a sphere A sphere (from Greek language, Greek —, "globe, ball") is a geometrical object in three-dimensional space Three-dimensional space (also: 3-space or, rarely, tri-dimensional s ...
used in
American football American football, referred to simply as football in the United States and Canada and also known as gridiron, is a team sport played by two teams of eleven players on a rectangular American football field, field with goalposts at each end. ...

American football
. Leather fetishism is the name popularly used to describe a
fetishistic A fetish (derived from the French language, French ''fétiche''; which comes from the Portuguese language, Portuguese ''feitiço''; and this in turn from Latin ''facticius'', "artificial" and ''facere'', "to make") is an object believed to have s ...
attraction to people wearing leather, or in certain cases, to the garments themselves. Many
rock group A musical ensemble, also known as a music group or musical group, is a group of people who perform instrumental An instrumental is a recording normally without any vocals, although it might include some inarticulate vocals, such as shouted ...
s (particularly
heavy metal Heavy metal may refer to: *Heavy metals, a loose category of relatively dense metals and metalloids **Toxic heavy metal, any heavy metal chemical element of environmental concern *Heavy metal music, a genre of rock music **Heavy metal genres *Hea ...
and
punk Punk or punks may refer to: Genres, subculture, and related aspects * Punk rock Punk rock (or simply punk) is a music genre that emerged in the mid-1970s. Rooted in 1960s garage rock, punk bands rejected the perceived excesses of mainstream 1 ...
groups in the 1970s and 80s) are well known for wearing leather clothing.
Extreme metal Extreme metal is a loosely defined umbrella term for a number of related heavy metal music subgenres that have developed since the early 1980s. It has been defined as a "cluster of metal subgenres characterized by sonic, verbal, and visual wikt: ...
bands (especially
black metal Black metal is an extreme subgenre of heavy metal music Heavy metal (or simply metal) is a genre of rock music Rock music is a broad genre of popular music Popular music is music with wide appeal that is typically distributed to ...
bands) and
Goth rock Gothic rock (alternately called goth-rock or goth) is a style of rock music Rock music is a broad genre of popular music that originated as "rock and roll" in the United States in the late 1940s and early 1950s, developing into a range of dif ...
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 Punk ideologies#Animal rights and veganism, punks who support animal rights. Many cars and trucks come with optional or standard leather or "leather faced" seating.


Religious sensitivities

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 ''Struthio'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a ...

ostrich
and deer. Judaism forbids the comfort of wearing leather shoes on Yom Kippur, Tisha B'Av, and during mourning. Also, see Tefillin, Teffilin and Sefer Torah, Torah Scroll. Jainism prohibits the use of leather, since it is obtained by killing animals.


Alternatives

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.


References


Further reading

* * * * * (includes several diagrams) {{Authority control Leather, Hides (skin)