Tanning , or hide tanning , is the process of treating skins and hides of animals to produce leather . A tannery is the place where the skins are processed.
60-513: The Caton Oak (also known as the Druid's Oak ) was an ancient oak tree that stood in Caton , Lancashire, reputedly dating from the time of the druids . The oak tree stood atop a set of steps known as the "Fish Stones" that were used by medieval monks to display salmon for sale. The tree declined during the 20th century and was reinforced with a metal support; an acorn from the tree was planted in 2007 to grow
120-550: A tannery . The English word for tanning is from medieval Latin tannāre , derivative of tannum ( oak bark ), from French tan (tanbark), from old-Cornish tann (oak). These terms are related to the hypothetical Proto-Indo-European * dʰonu meaning ' fir tree'. (The same word is source for Old High German tanna meaning 'fir', related to modern German Tannenbaum ). Ancient civilizations used leather for waterskins , bags, harnesses and tack, boats, armour , quivers , scabbards , boots , and sandals . Tanning
180-441: A bath solution containing vegetable tannins, such as found in gallnuts , the leaves of sumac , the leaves of certain acacia trees, the outer green shells of walnuts , among other plants. The use of vegetable tanning is a process that takes longer than mineral tanning when converting rawhides into leather. Mineral tanned leather is used principally for shoes, car seats, and upholstery in homes (sofas, etc.). Vegetable tanned leather
240-427: A high content of glycine , proline , and hydroxyproline , usually in the repeat -gly-pro-hypro-gly-. These residues give rise to collagen's helical structure. Collagen's high content of hydroxyproline allows cross-linking by hydrogen bonding within the helical structure. Ionized carboxyl groups (RCO 2 ) are formed by the action of hydroxide. This conversion occurs during the liming process, before introduction of
300-480: A large factor in how hazardous wastewater results in contaminating the environment. This is especially prominent in small and medium-sized tanneries in developing countries. The UN Leather Working Group (LWG) "provides an environmental audit protocol, designed to assess the facilities of leather manufacturers," for "traceability, energy conservation, [and] responsible management of waste products." Untanned hides can be dried and made pliable by rubbing and stretching
360-506: A local landmark and a symbol of the village, featuring in the logos of the village school and its sports club. A sign affixed to railings around the tree states that it has been listed as a historic site by the Department of National Heritage . A Caton-with-Littledale parish councillor said in 1996 that "the tree is the most important landmark in Caton and we should try to preserve it as long as there
420-621: A narrow belt along the Himalayas to cover mainland and island Southeast Asia as far as Sumatra , Java , Borneo , and Palawan . Finally, oaks of multiple sections ( Cyclobalanopsis , Ilex , Cerris , Quercus and related genera like Lithocarpus and Castanopsis ) extend across east Asia including China, Korea, and Japan. Potential records of Quercus have been reported from Late Cretaceous deposits in North America and East Asia. These are not considered definitive, as macrofossils older than
480-485: A range of flavours, colours, and aromas. The spongy bark of the cork oak is used to make traditional wine bottle corks. Almost a third of oak species are threatened with extinction due to climate change, invasive pests , and habitat loss . In culture, the oak tree is a symbol of strength and serves as the national tree of many countries. In Indo-European and related religions, the oak is associated with thunder gods . Individual oak trees of cultural significance include
540-453: A replacement. The original Caton Oak fell on 20 June 2016. The Caton is reputed to have been the focus of the village since the era of the druids, for whom the oak was a sacred tree which often formed the centre of religious rites. For this reason the tree is also known as the Druid's Oak. There was activity in the village during Roman times, as evidenced by a millstone found nearby. The Caton Oak
600-508: A single oak tree produces both staminate ('male') flowers in the form of catkins , and small pistillate ('female') flowers, meaning that the trees are monoecious . The fruit is a nut called an acorn , borne in a cup-like structure known as a cupule ; each acorn usually contains one seed and takes 6–18 months to mature, depending on the species. The acorns and leaves contain tannic acid , which helps to guard against fungi and insects. There are some 500 extant species of oaks. Trees in
660-400: A skin at a slaughterhouse, farm, or local fur trader. Before tanning, the skins are often dehaired, then have fat, meat and connective tissue removed. They are then washed and soaked in water with various compounds, and prepared to receive a tanning agent. They are then soaked, stretched, dried, and sometimes smoked. Preparing hides begins by curing them with salt to prevent putrefaction of
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#1733085246511720-546: A small area of the west of Cuba ; in Mesoamerica it occurs mainly above 1000 metres. The genus crossed the isthmus of Panama when the northern and southern continents came together and is present as one species, Q. humboldtii , above 1000 metres in Colombia. The oaks of North America are of many sections ( Protobalanus , Lobatae , Ponticae , Quercus , and Virentes ) along with related genera such as Notholithocarpus . In
780-489: Is any life in it at all". The village of Caton lies within the Forest of Bowland area of outstanding natural beauty . The tree declined during the later 20th century and was said to have become dangerous by 1996. Specialists were consulted who recommended that the tree be felled but it was saved by the villagers and the parish council who erected metal props to the branch in question. The improvements were carried out in 1998 under
840-419: Is considered one of the most effective tanning compounds. Chromium-tanned leather can contain between 4 and 5% of chromium. This efficiency is characterized by its increased hydrothermal stability of the skin, and its resistance to shrinkage in heated water. Vegetable tanning uses tannins (a class of polyphenol astringent chemicals), which occur naturally in the bark and leaves of many plants. Tannins bind to
900-403: Is consistent with cross-linking by polychromium species, of the sort arising from olation and oxolation. Before the introduction of the basic chromium species in tanning, several steps are required to produce a tannable hide. The pH must be very acidic when the chromium is introduced to ensure that the chromium complexes are small enough to fit between the fibers and residues of the collagen. Once
960-416: Is excellent for use in handbags and garments. After application of the chromium agent, the bath is treated with sodium bicarbonate in the basification process to increase the pH to 3.8–4.0, inducing cross-linking between the chromium and the collagen. The pH increase is normally accompanied by a gradual temperature increase up to 40 °C. Chromium's ability to form such stable bridged bonds explains why it
1020-452: Is from Old English ac (seen in placenames such as Acton , from ac + tun , "oak village" ), which in turn is from Proto-Germanic *aiks , "oak". Oaks are hardwood ( dicotyledonous ) trees, deciduous or evergreen, with spirally arranged leaves , often with lobate margins ; some have serrated leaves or entire leaves with smooth margins. Many deciduous species are marcescent , not dropping dead leaves until spring. In spring,
1080-419: Is not very flexible. It is used for luggage, furniture, footwear, belts, and other clothing accessories. Wet white is a term used for leathers produced using alternative tanning methods that produce an off-white colored leather. Like wet blue, wet white is also a semifinished stage. Wet white can be produced using aldehydes , aluminum, zirconium, titanium, or iron salts, or a combination thereof. Concerns with
1140-428: Is preferred. Once bating is complete, the hides and skins are treated by first soaking them in a bath containing common salt (sodium chloride), usually 1 quart of salt to 1 gallon of hot water. When the water cools, one fluid ounce of sulfuric acid is added. Small skins are left in this liquor for 2 days, while larger skins between 1 week and as much as 2 months. In vegetable tanning, the hides are made to soak in
1200-551: Is rooted in the River Lune and the trunk protrudes above a set of old sandstone steps known as the "Fish Stones". In Medieval times monks from Cockersand Abbey used the steps to display for sale salmon that had been caught in the river. The tree can be seen to be in good health in a photograph of 1905. By the 1940s the tree was the site for a portable blacksmith's forge where a smith from nearby Hornby regularly set up to shoe horses for Caton's agricultural community. The tree became
1260-421: Is tawed by soaking in a warm potash alum and salts solution, between 20 and 30 °C (68 and 86 °F). The process increases the hide's pliability, stretchability, softness, and quality. Then, the hide is air dried (crusted) for several weeks, which allows it to stabilize. The use of alum alone for tanning rawhides is not recommended, as it shrinks the surface area of the skin, making it thicker and hard to
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#17330852465111320-420: Is the characteristic of the keratin class of proteins that gives strength to hair and wools (keratin typically makes up 90% of the dry weight of hair). The hydrogen atoms supplied by the sharpening agent weaken the cystine molecular link whereby the covalent disulfide bond links are ultimately ruptured, weakening the keratin. To some extent, sharpening also contributes to unhairing, as it tends to break down
1380-439: Is used as a leather tanning agent, can cause problems in the kidneys and liver and is also considered a carcinogen . Formaldehyde and arsenic, which are used for leather finishing, cause health problems in the eyes, lungs, liver, kidneys, skin, and lymphatic system and are also considered carcinogens. The waste from leather tanneries is detrimental to the environment and the people who live in it. The use of old technologies plays
1440-461: Is used in leather crafting and in making small leather items, such as wallets, handbags and clothes. Chromium(III) sulfate ( [Cr(H 2 O) 6 ] 2 (SO 4 ) 3 ) has long been regarded as the most efficient and effective tanning agent. Chromium(III) compounds of the sort used in tanning are significantly less toxic than hexavalent chromium , although the latter arises in inadequate waste treatment. Chromium(III) sulfate dissolves to give
1500-622: The Paleogene , and possibly from before the Eocene are mostly poorly preserved without critical features for certain identification. Amongst the oldest unequivocal records of Quercus are pollen from Austria, dating to the Paleocene -Eocene boundary, around 55 million years ago. The oldest records of Quercus in North America are from Oregon , dating to the Middle Eocene, around 44 million years ago, with
1560-810: The Royal Oak in Britain, the Charter Oak in the United States, and the Guernica Oak in the Basque Country . The generic name Quercus is Latin for "oak", derived from Proto-Indo-European *kwerkwu- , "oak", which is also the origin of the name " fir ", another important or sacred tree in Indo-European culture. The word "cork", for the bark of the cork oak , similarly derives from Quercus . The common name "oak"
1620-436: The oak apple , and a large number of pests and diseases. Oak leaves and acorns contain enough tannin to be toxic to cattle, but pigs are able to digest them safely. Oak timber is strong and hard, and has found many uses in construction and furniture-making. The bark was traditionally used for tanning leather . Wine barrels are made of oak; these are used for aging alcoholic beverages such as sherry and whisky , giving them
1680-591: The Middle Eocene . Molecular phylogeny shows that the genus is divided into Old World and New World clades , but many oak species hybridise freely, making the genus's history difficult to resolve. Ecologically, oaks are keystone species in habitats from Mediterranean semi-desert to subtropical rainforest . They live in association with many kinds of fungi including truffles . Oaks support more than 950 species of caterpillar , many kinds of gall wasp which form distinctive galls , roundish woody lumps such as
1740-687: The Old World, oaks of section Quercus extend across the whole of Europe including European Russia apart from the far north, and north Africa (north of the Sahara) from Morocco to Libya. In Mediterranean Europe, they are joined by oaks of the sections Cerris and Ilex , which extend across Turkey, the Middle East, Iran, Afghanistan and Pakistan , while section Ponticae is endemic to the western Caucasus in Turkey and Georgia . Oaks of section Cyclobalanopsis extend in
1800-614: The Parish and Community Environment Scheme funded by Lancashire County Council, Caton-with-Littledale Parish Council, Rural Action and public contributions. By 2007 the trunk, which measured 4 metres (13 ft) in circumference, was hollow through decay. On 27 April 2007 an acorn from the tree was planted within the hollow by the High Sheriff of Lancashire (Ruthe Winterbottom) so that a replacement tree could grow. The new tree would have killed
1860-411: The adoption in medicine of soaking gut sutures in a chromium (III) solution after 1840, it was discovered that this method could also be used with leather and thus was adopted by tanners. The tanning process begins with obtaining an animal skin. When an animal skin is to be tanned, the animal is killed and skinned before the body heat leaves the tissues. This can be done by the tanner, or by obtaining
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1920-408: The bark of certain trees, in the production of leather. An alternative method, developed in the 1800s, is chrome tanning, where chromium salts are used instead of natural tannins. Tanning hide into leather involves a process which permanently alters the protein structure of skin, making it more durable and less susceptible to decomposition and coloring. The place where hides are processed is known as
1980-485: The case of Bangladesh, chickens (the nation's most common source of protein). Up to 25% of the chickens in Bangladesh contained harmful levels of hexavalent chromium, adding to the national health problem load. Chromium is not solely responsible for these diseases. Methylisothiazolinone , which is used for microbiological protection (fungal or bacterial growth), causes problems with the eyes and skin. Anthracene , which
2040-436: The collagen from bacterial growth during the time lag from procuring the hide to when it is processed. Curing removes water from the hides and skins using a difference in osmotic pressure. The moisture content of hides and skins is greatly reduced, and osmotic pressure increased, to the point that bacteria are unable to grow. In wet-salting, the hides are heavily salted, then pressed into packs for about 30 days. In brine -curing,
2100-459: The collagen proteins in the hide and coat them, causing them to become less water-soluble and more resistant to bacterial attack. The process also causes the hide to become more flexible. The primary barks processed in bark mills and used in modern times are chestnut , oak , redoul , tanoak , hemlock , quebracho , mangrove , wattle (acacia; see catechol ), and myrobalans from Terminalia spp., such as Terminalia chebula . In Ethiopia ,
2160-416: The collagen's carboxyl groups, amine groups from the side chains of the amino acids , and masking agents. Masking agents are carboxylic acids , such as acetic acid , used to suppress formation of polychromium(III) chains. Masking agents allow the tanner to further increase the pH to increase collagen's reactivity without inhibiting the penetration of the chromium(III) complexes. Collagen is characterized by
2220-540: The combined vegetable oils of Niger seed ( Guizotia abyssinica ) and flaxseeds were used in treating the flesh side of the leather, as a means of tawing, rather than of tanning. In Yemen and Egypt , hides were tanned by soaking them in a bath containing the crushed leaves and bark of the Salam acacia (Acacia etbaica; A. nilotica kraussiana). Hides that have been stretched on frames are immersed for several weeks in vats of increasing concentrations of tannin. Vegetable-tanned hide
2280-409: The desired level of penetration of chrome into the substance is achieved, the pH of the material is raised again to facilitate the process. This step is known as basification. In the raw state, chrome-tanned skins are greyish-blue, so are referred to as wet blue . Chrome tanning is faster than vegetable tanning (taking less than a day for this part of the process) and produces a stretchable leather which
2340-425: The end use of the leather, hides may be treated with enzymes to soften them, a process called bating . In modern tanning, these enzymes are purified agents, and the process no longer requires bacterial fermentation (as from dung-water soaking) to produce them. Pickling is another term for tanning, or what is the modern equivalent of turning rawhide into leather by the use of modern chemical agents, if mineral tanning
2400-562: The fibers with a hide stretcher, and fatting. However the hide will revert to rawhide if not periodically replenished with fat or oil, especially if it gets wet. Many Native Americans of the arid western regions wore clothing made by this process. Smoke tanning is listed among the conventional methods like chrome tanning and vegetable tanning. Impregnation of the hide's cells with formaldehyde (from smoke) offers some microbial and water resistance. Leftover leather would historically be turned into glue . Tanners would place scraps of hides in
2460-404: The genus Quercus consisted of Old World and New World clades. The entire genome of Quercus robur (the pedunculate oak) has been sequenced , revealing an array of mutations that may underlie the evolution of longevity and disease resistance in oaks. In addition, hundreds of oak species have been compared (at RAD-seq loci), allowing a detailed phylogeny to be constructed. However,
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2520-625: The genus are often large and slow-growing; Q. alba can reach an age of 600 years, a diameter of 13 feet (4.0 m) and a height of 145 feet (44 m). The Granit oak in Bulgaria, a Q. robur specimen, has an estimated age of 1637 years, making it the oldest oak in Europe. The Wi'aaSal tree, a live oak in the reservation of the Pechanga Band of Indians , California, is at least 1000 years old, and might be as much as 2000 years old, which would make it
2580-418: The hair proteins. The isoelectric point of the collagen (a tissue-strengthening protein unrelated to keratin) in the hide is also shifted to around pH 4.7 due to liming. Any hairs remaining after liming are removed mechanically by scraping the skin with a dull knife, a process known as scudding. The pH of the collagen is then reduced so the enzymes may act on it in a process known as deliming. Depending on
2640-406: The hexaaquachromium(III) cation, [Cr(H 2 O) 6 ] , which at higher pH undergoes processes called olation to give polychromium(III) compounds that are active in tanning, being the cross-linking of the collagen subunits. The chemistry of [Cr(H 2 O) 6 ] is more complex in the tanning bath rather than in water due to the presence of a variety of ligands. Some ligands include the sulfate anion,
2700-459: The hides are agitated in a saltwater bath for about 16 hours. Curing can also be accomplished by preserving the hides and skins at very low temperatures. The steps in the production of leather between curing and tanning are collectively referred to as beamhouse operations. They include, in order, soaking, liming , removal of extraneous tissues (unhairing, scudding and fleshing), deliming , bating or puering, drenching, and pickling. In soaking,
2760-406: The hides are soaked in clean water to remove the salt left over from curing and increase the moisture so that the hide or skin can be further treated. To prevent damage of the skin by bacterial growth during the soaking period, biocides , typically dithiocarbamates , may be used. Fungicides such as TCMTB may also be added later in the process, to protect wet leathers from mold growth. After 1980,
2820-1202: The high signal of introgressive hybridization (the transfer of genetic material by repeated backcrossing with hybrid offspring) in the genus has made it difficult to resolve an unambiguous, unitary history of oaks. The phylogeny from Hipp et al. 2019 is: CTB lineage [REDACTED] Cyclobalanoides Glauca [REDACTED] Acuta [REDACTED] Semiserrata East Asian Cerris [REDACTED] West Eurasian Cerris [REDACTED] Early-diverging Ilex [REDACTED] East Asian Ilex [REDACTED] Himalaya-Mediterranean [REDACTED] Himalayan subalpine [REDACTED] Agrifoliae [REDACTED] Palustres [REDACTED] Coccineae (Rubrae) [REDACTED] Phellos (Laurifoliae) [REDACTED] Texas red oaks [REDACTED] Erythromexicana [REDACTED] [REDACTED] [REDACTED] [REDACTED] Dumosae [REDACTED] Prinoids [REDACTED] Albae [REDACTED] Roburoids [REDACTED] Stellatae [REDACTED] Texas white oaks [REDACTED] Leucomexicana [REDACTED] Tanning leather Historically, vegetable based tanning used tannin , an acidic chemical compound derived from
2880-510: The largest number of oak species, with approximately 160 species in Mexico, of which 109 are endemic, and about 90 in the United States. The second greatest area of oak diversity is China, with approximately 100 species. In the Americas, Quercus is widespread from Vancouver and Nova Scotia in the south of Canada, south to Mexico and across the whole of the eastern United States. It is present in
2940-545: The old tree as it grows within it. The original Caton oak fell on 20 June 2016. Oak See also List of Quercus species . An oak is a hardwood tree or shrub in the genus Quercus of the beech family . They have spirally arranged leaves, often with lobed edges, and a nut called an acorn , borne within a cup. The genus is widely distributed in the Northern Hemisphere; it includes some 500 species, both deciduous and evergreen . Fossil oaks date back to
3000-547: The oldest oak in the US. Among the smallest oaks is Q. acuta , the Japanese evergreen oak. It forms a bush or small tree to a height of some 30 feet (9.1 m). The genus Quercus is native to the Northern Hemisphere and includes deciduous and evergreen species extending from cool temperate to tropical latitudes in the Americas , Asia, Europe, and North Africa. North America has
3060-855: The oldest records in Asia from the Middle Eocene of Japan; both forms have affinities to the Cyclobalanopsis group. Quercus forms part, or rather two parts, of the Quercoideae subfamily of the Fagaceae , the beech family. Modern molecular phylogenetics suggests the following relationships: Fagus (beeches) Trigonobalanus (3 evergreen species) Lithocarpus (stone oaks) Chrysolepis (chinquapins) Quercus pro parte Notholithocarpus (tan oak) Quercus pro parte Castanopsis (also called chinquapins) Castanea (chestnuts) Molecular techniques for phylogenetic analysis show that
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#17330852465113120-427: The outskirts of town, among the poor. Tanning by ancient methods is so foul-smelling that tanneries are still isolated from those towns today where the old methods are used. Skins typically arrived at the tannery dried stiff and dirty with soil and gore. First, the ancient tanners would soak the skins in water to clean and soften them. Then they would pound and scour the skin to remove any remaining flesh and fat . Hair
3180-508: The process. Chemicals used in tanned leather production increase the levels of chemical oxygen demand and total dissolved solids in water when not disposed of responsibly. These processes also use large quantities of water and produce large amounts of pollutants. Boiling and sun drying can oxidize and convert the various chromium(III) compounds used in tanning into carcinogenic hexavalent chromium , or chromium(VI). This hexavalent chromium runoff and scraps are then consumed by animals, in
3240-403: The tanning agent (chromium salts). Later during pickling, collagen carboxyl groups are temporarily protonated for ready transport of chromium ions. During basification step of tanning, the carboxyl groups are ionized and coordinate as ligands to the chromium(III) centers of the oxo-hydroxide clusters. Tanning increases the spacing between protein chains in collagen from 10 to 17 Å. The difference
3300-407: The touch. If alum is applied to the fur, it makes the fur dull and harsh. Depending on the finish desired, the leather may be waxed, rolled, lubricated, injected with oil, split, shaved, or dyed. The tanning process involves chemical and organic compounds that can have a detrimental effect on the environment. Agents such as chromium, vegetable tannins, and aldehydes are used in the tanning step of
3360-492: The toxicity and environmental impact of any chromium (VI) that may form during the tanning process have led to increased research into more efficient wet white methods. The conditions present in bogs, including highly acidic water, low temperature, and a lack of oxygen, combine to preserve but severely tan the skin of bog bodies . Tawing is a method that uses alum and other aluminium salts , generally in conjunction with binders such as egg yolk, flour, or other salts. The hide
3420-418: The use of pentachlorophenol and mercury -based biocides and their derivatives was forbidden. After soaking, the hides are treated with milk of lime (a basic agent) typically supplemented by "sharpening agents" (disulfide reducing agents) such as sodium sulfide , cyanides , amines , etc. This: The weakening of hair is dependent on the breakdown of the disulfide link of the amino acid cystine , which
3480-419: Was a fermentative process that relied on enzymes produced by bacteria found in the dung. Among the kinds of dung commonly used were those of dogs or pigeons. Historically the actual tanning process used vegetable tanning. In some variations of the process, cedar oil , alum , or tannin was applied to the skin as a tanning agent. As the skin was stretched, it would lose moisture and absorb the agent. Following
3540-523: Was being carried out by the inhabitants of Mehrgarh in Pakistan between 7000 and 3300 BCE. Around 2500 BCE , the Sumerians began using leather, affixed by copper studs , on chariot wheels . The process of tanning was also used for boats and fishing vessels: ropes, nets, and sails were tanned using tree bark. Formerly, tanning was considered a noxious or "odoriferous trade" and relegated to
3600-424: Was removed by soaking the skin in urine , painting it with an alkaline lime mixture, or simply allowing the skin to putrefy for several months then dipping it in a salt solution. After the hair was loosened, the tanners scraped it off with a knife. Once the hair was removed, the tanners would " bate " (soften) the material by pounding dung into the skin, or soaking the skin in a solution of animal brains. Bating
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