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A variety of leather products and leather-working tools

Leather is a durable and flexible material created by "tanning animal "rawhide and skin, often cattle hide. It can be produced at manufacturing scales ranging from "cottage industry to "heavy industry.

People use leather to make various goods—including clothing (e.g., shoes, hats, jackets, skirts, trousers, and belts), "bookbinding, "leather wallpaper, and as a furniture covering. It is produced in a wide variety of types and styles, decorated by a wide range of techniques.

Contents

Forms[edit]

Several tanning processes transform hides and skins into leather:

Leather, usually vegetable-tanned, 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. "Russia leather was an important international "trade good for centuries.["citation needed][1] Frequent oiling of leather, with "mink oil, "neatsfoot oil, or a similar material keeps it supple and improves its lifespan dramatically.["citation needed][2]

Leather with the hair still attached is called "hair-on".["citation needed]

Types[edit]

In general, leather is sold in these four forms:

Less-common leathers include:

There are two other types of leather commonly used in specialty products, such as briefcases, wallets, and luggage:

The following are not "true" leathers, but are materials that contain some leather fiber. Depending on jurisdiction, they may still be labeled as "Genuine Leather", even though the consumer generally can only see the outer layer of the material and can't actually see any of the leather content:

From other animals[edit]

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Phone cases in "ostrich leather

Today, most leather is made of "cattle skin, but many exceptions exist. Lamb and deerskin are used for soft leather in more expensive apparel. Deer and elkskin are widely used in work gloves and indoor shoes. Pigskin is used in apparel and on seats of "saddles. Buffalo, goat, alligator, "snake, ostrich, kangaroo, ox, and yak skins may also be used for leather.

"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.[11] Kangaroo leather[12] is also used for falconry jesses, soccer footwear,[13] and boxing speed bags.[14] At different times in history, leather made from more exotic skins has been considered desirable. For this reason, certain species of snakes and crocodiles have been hunted.

Although originally raised for their feathers in the 19th century, "ostriches are now more popular for both meat and leather.[15] Different processes produce different finishes for many applications, i.e., upholstery, footwear, automotive products, accessories, and clothing. "Ostrich leather is currently used by many major fashion houses such as "Hermès, "Prada, "Gucci, and "Louis Vuitton. Ostrich leather has a characteristic "goose bump" look because of the large follicles where the feathers grew.

In "Thailand, "stingray leather is used in wallets and belts. Sting ray 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.)

Production processes[edit]

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Drying of leather in "East Timor
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Leather tanning in "Fes, "Morocco
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Tanned leather in "Marrakech

The leather manufacturing process is divided into three fundamental subprocesses: preparatory stages, tanning, and crusting. All true leathers undergo these subprocesses. A further subprocess, surface coating, can be added into the leather process sequence, but not all leathers receive surface treatment. Since many types of leather exist, it is difficult to create a list of operations that all leathers must undergo.

The preparatory stages are when the hide/skin is prepared for tanning. Preparatory stages may include: preservation, soaking, "liming, unhairing, fleshing, splitting, reliming, "deliming, bating, "degreasing, frizing, "bleaching, "pickling, and depickling.

"Tanning is a process that stabilizes the "protein of the raw hide or skin 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 (or wetted-back) putrefy, while tanned material dries to a flexible form that does not become putrid when wetted-back.

Many tanning methods and materials exist. The choice ultimately depends on the end application for the leather. The most common tanning material is "chromium, which leaves the tanned leather a pale blue color (due to the chromium). This product is commonly called wet blue. The hides, when finished pickling, are typically between "pH 2.8 and 3.2.["citation needed] At this point, tannery workers load the hides into a drum and immerse them in a float 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. Workers periodically cut a cross-section of a hide and observe the degree of penetration. Once the process achieves even penetration, workers slowly raise the float's pH in a process called basification, which fixes the tanning material to the leather—and 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.["citation needed]

Crusting is a process that thins, retans, 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:

For some leathers, workers apply a surface coating. Tanners call this finishing. Finishing operations can include:

Environmental impact[edit]

Leather produces some environmental impact, most notably due to:

Carbon footprint[edit]

One estimate of the "carbon footprint of leather goods is 0.51 kg of CO2 equivalent per £1 of output at 2010 retail prices, or 0.71 kg CO2eq per £1 of output at 2010 industry prices.[16]

Water footprint[edit]

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.[17]

Disposal[edit]

Leather "biodegrades slowly—taking 25 to 40 years to "decompose.[18]["citation needed] However, vinyl and petrochemical-derived materials take 500 or more years to decompose.["citation needed]

Chemicals used in tanning[edit]

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[19] 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.[20] In 2003 for instance, the main tanneries' effluent disposal unit was dumping 22 tonnes of chromium-laden solid waste per day in the open.[21] Scientists at the Central Leather Research Institute in India have developed biological methods for pretanning, as well as better chromium management.

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. Besides local sales of products made with leather from the Hazaribagh neighborhood of Dhaka, the leather is also bought by huge Western companies and sold in the developed world.[22][23] After approximately 15 years of ignoring high court rulings, the government moved more than 100 tanneries the weekend of April 8, 2017 in Hazaribagh neighborhood.[24]

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.[25]

No general study seems to exist, but recent media reports are rife with examples.["clarification needed] In November 2009, for example, one of Uganda's main leather companies was caught directly dumping waste water into a wetland adjacent to "Lake Victoria.[26]

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Rajasthani style Leather Jooti,local artwork Jaipur India 1
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Rajasthani style Leather Jooti,local artwork Jaipur India


Role of enzymes[edit]

"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.[27]

Lipases are used in the degreasing operation to hydrolyze fat particles embedded in the skin.[28]

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[edit]

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.[29]

Leather book binding[edit]

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A set of leather-bound books

Leather used in "book binding has many of the same preservation needs: protection from high temperatures, high relative humidity, low relative humidity, fluctuations in relative humidity, light exposure, dust buildup, pollution, mold, and insect infestation.[30][31][32]

For books with red rot, acid-free phase boxes and/or polyester dust jackets (Dupont Mylar Type D or ICI Mellinex 516) are recommended to protect the leather from further handling damage and to prevent the residues from getting on hands, clothes, the text block, and nearby books.[33]

The debate on the use of dressings for preservation of book bindings has spanned several decades as research and experimental evidence have slowly accumulated. The main argument is, when done incorrectly, multiple disadvantages exist, and when done correctly, little to no preservation advantage occurs. Pamphlets and guidelines give numerous downsides to dressings use, including: the dressing becoming increasingly acidic and discolors and stains the leather, oxidizes (penetration and expansion of oils including displacement and weakening of fibers) and stiffens, leave a sticky surface, collects dust, wicks into adjacent materials, forms unstable surface spews, encourages biological deterioration and mold growth, blocks surface porosity, impedes further treatment, wets and swells the leather, affects surface finishes, and desiccates the leather.[34] Meanwhile, scientific experiments have shown no substantial benefits.[35] The main authorities on the subject, therefore, discourage it, with a caveat for special cases done under the direction of a conservator.[30][33][34] Leather can be decorated by a variety of methods, including "pyrography and "beading.

Cordwain and Cuir de Cordoue[edit]

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Fragment of "Cuir de Cordoue

Cordwain, once a synonym of "cordovan (through "Old French cordewan) meaning "from "Córdoba" describes a certain kind of fine leather, originally from Córdoba. Cordwainer is still used to describe someone in the profession of "shoemaking.

The related term Cuir de Cordoue refers to painted and "gilded (and sometimes "embossed) leather hangings manufactured in panels and assembled for covering walls as an alternative to "tapestry.

In modern culture[edit]

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. Many sports still use leather equipment. Its flexibility facilitates forming and shaping it into balls and protective gear.

"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 1980s) are well known for wearing leather clothing. Leather clothing, particularly jackets, are common in the heavy metal and Punk subculture. "Extreme metal bands (especially "black metal bands) and "Goth rock groups have extensive leather clothing.

Many cars and trucks come with optional or standard "leather" seating.

Religious sensitivities[edit]

In some religiously diverse countries, leather vendors typically clarify the kinds of leather in their products. For example, leather shoes bear a label that identifies the animal from which the leather came. This helps a "Muslim not accidentally purchase pigskin, and a "Hindu avoid cattle. Many vegetarian Hindus do not use any kind of leather. 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.[36]

"Jainism prohibits the use of leather, since it is obtained by killing animals.

Alternatives[edit]

Some vegetarians, "vegans and "animal rights activists and groups such as "PETA, "boycott and promote the boycotting of all leather products, arguing that the use of leather is unjustifiable. They encourage the use of alternative materials such as "synthetic leathers.

Many synthetic leather materials have been developed. Some published claims assert that certain versions of artificial leather are stronger than real leather when manufactured with strength in mind. Ranges of synthetic "polymeric materials provide features rivalling or exceeding those of various types of leather in particular applications; they include vegan "microfiber, "pleather and "Naugahyde.[37]

See also[edit]

Types
Substitutes
Fabrication
Other

References[edit]

  1. ^ Holtrop, edited by Pieter; Slechte, Henk (2007). Foreign churches in St. Petersburg and their archives, 1703-1917 ([Online-Ausg.]. ed.). Leiden: Brill. p. 34. "ISBN "9789004162600. Archived from the original on 28 November 2017. Retrieved 30 March 2017. 
  2. ^ Leather Processing & Tanning Technology Handbook. NIIR Project Consultancy Services. 2011. p. 323. "ISBN "9788190568593. Archived from the original on 28 November 2017. Retrieved 30 March 2017.  |first1= missing |last1= in Authors list ("help)
  3. ^ "IULTCS Glossary of Leather Terms". Archived from the original on 27 March 2004. Retrieved 15 June 2010. 
  4. ^ RTL TVI "I comme Islande" - Processus de fabrication du cuir de poisson - Video Dailymotion. Dailymotion.com. Retrieved on 19 November 2016.
  5. ^ "NAS - Nonindigenous Aquatic Species". USGS. Archived from the original on 14 July 2014. Retrieved 10 June 2014. 
  6. ^ Ehrenreich, Alfred. "assignee=alfred+ehrenreich". Google Patents. Retrieved 21 November 2017. 
  7. ^ Castro, Jose I. (2013) Historical knowledge of sharks: ancient science, earliest American encounters, and American science, fisheries, and utilization. Marine Fisheries Review, 75(4), pp. 1-26. 10.7755/MFR.75.4.1
  8. ^ Bennett, Mick (26 September 2017). Leather Bags for Women: An Overview from 3,000 Designs. Lulu Press, Inc. p. 4. "ISBN "9781387232031. Archived from the original on 25 October 2017. 
  9. ^ RUBEL, MD MIZANUR RAHMAN. Quality Control Technique: Leather Products Cutting Department. Lulu.com. p. 12. "ISBN "9781304320391. Archived from the original on 25 October 2017. 
  10. ^ Binggeli, Corky (26 August 2013). Materials for Interior Environments. John Wiley & Sons. p. 119. "ISBN "9781118421604. Archived from the original on 25 October 2017. 
  11. ^ "FAQ". Dainese. Retrieved 5 October 2010. 
  12. ^ Lat, Will. "Soccer Cleats". Archived from the original on 19 October 2012. Retrieved 3 October 2012. 
  13. ^ "What type of Leather do I have?". Soccer Cleats 101. Retrieved 27 July 2010. 
  14. ^ "Everlast Premium Kangaroo Leather Speed Bag". Everlast. Retrieved 20 October 2013. 
  15. ^ Henrylito Tacio,"Why You Should Raise Ostrich," Sun.Star 18 January 2010. Archived 24 December 2013 at the "Wayback Machine.
  16. ^ Mike Berners-Lee, How Bad are Bananas: The Carbon Footprint of Everything (London: Profile, 2010), p. 201.
  17. ^ "Pollution Prevention and Abatement Handbook - Environmental Guidelines for Tanning and Leather Finishing" (PDF). Multilateral Investment Guarantee Agency, World Bank Group. Retrieved 2 January 2010. 
  18. ^ "Measuring biodegradability". Sciencelearn Hub. Archived from the original on 20 January 2017. Retrieved 25 January 2017. 
  19. ^ "The scope for decreasing pollution load in leather processing (US/RAS/92/120/11-51)" (PDF). United Nations Industrial Development Organization Regional Programme for Pollution Control in the Tanning Industry in South-East Asia. 9 August 2000. Retrieved 2 January 2010. ["permanent dead link]
  20. ^ "How much time needed to check tanneries' waste". Times of India. 11 July 2009. Archived from the original on 5 December 2010. Retrieved 2 January 2010. 
  21. ^ "Kanpur: chromium disaster". Clean Ganga - Campaign for a cleaner Ganga. June 2003. Archived from the original on 22 August 2003. Retrieved 2 January 2010. 
  22. ^ Hazaribagh neighborhood of Dhaka poisoning staff, local villagers and planet Archived 28 March 2017 at the "Wayback Machine.. Hrw.org (8 October 2012). Retrieved on 2016-11-19.
  23. ^ Documentary by Upside Télévision
  24. ^ "Bangladesh cuts power to leather district after years of environmental violations". PBS NewsHour. Archived from the original on 12 April 2017. Retrieved 11 April 2017. 
  25. ^ "Introduction of Low Pollution Processes in Leather Production" (PDF). EcoLinks. 2001. Archived from the original (PDF) on 19 January 2010. Retrieved 2 January 2010. 
  26. ^ "Uganda: leather factory faces closure over pollution". The Monitor. 5 November 2009. Archived from the original on 4 June 2011. Retrieved 2 January 2010. 
  27. ^ Heidemann, E. (1993). Fundamentals of Leather Manufacture. Eduard Roether KG. p. 211. "ISBN "3-7929-0206-0. 
  28. ^ Bienkiewicz, K. (1983). Physical Chemistry of Leather Making. Robert E. Krieger. p. 226. "ISBN "0-89874-304-4. 
  29. ^ "Maintain Lather Bag". larocco. Archived from the original on 3 June 2016. Retrieved 4 May 2016. 
  30. ^ a b John Mumford. "Understanding and Caring for Bookbindings" (PDF). The British Library. Archived from the original (PDF) on 2 October 2008. Retrieved 6 October 2010. 
  31. ^ Mary Fahey. "The Care and Preservation of Archival Materials". "The Henry Ford. Archived from the original on 7 December 2003. Retrieved 6 April 2008. 
  32. ^ The Henry Ford. "The Care and Preservation of Archival Materials". 
  33. ^ a b "Leather Dressing". Library of Congress. Archived from the original on 2 April 2008. Retrieved 5 April 2008. 
  34. ^ a b "Leather Dressing: 'To Dress or not to Dress'". National Park Service Conserve O Gram. Society of Rocky Mountain Archivists. 9 (1). December 2004. Archived from the original on 23 September 2006. Retrieved 5 April 2008. 
  35. ^ McCrady, Ellen. "Research on the Dressing and Preservation of Leather. Abbey Newsletter, Vol. 5 No. 2, 1981-04". palimpsest.stanford.edu. Archived from the original on 17 September 2008. Retrieved 6 October 2010. 
  36. ^ "Wearing Shoes - Mourning Observances of Shiva and Sheloshim". Chabad.org. Archived from the original on 22 December 2009. Retrieved 20 October 2009. 
  37. ^ Artificial Leather- An Eco-friendly Alternative Textile Material For Leather["permanent dead link] Jahan, Saurabh and Jahan, Shahnaz. China Textile Science 3rd 2011.

Further reading[edit]

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