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57-439: Tanyard may refer to: The yard of a tannery, see Tanning (leather) Tanyard, Maryland , an unincorporated community Tanyard Branch (disambiguation) Tanyard Creek (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Tanyard . If an internal link led you here, you may wish to change

114-550: 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

171-441: 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

228-427: 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

285-464: A hole found, they sew it, and then lay them out over a wooden frame that is prepared in advance [for this purpose] and they rinse them thoroughly with running water [=drenching], and then bring out a heaping batch of gallnuts which they then pound or grind thoroughly. They then put on each sheet of leather three litres of the Baghdad measure, and plaster thereon the gallnuts, over its two sides, and sprinkle

342-480: 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

399-405: A little water over them, and they put more gallnuts on that side of the leather where the hairs once were (grain layer) than what they do on the flesh-side [of the leather], doing likewise with each sheet of leather, the application [of gallnuts] made twice daily, while, on the third application, they once more plaster with what remains of the gallnuts [onto the leather] and lay it out in the sun, for

456-405: A natural bate. Papain , the active proteolytic enzyme found in the latex taken from the skin of the papaya fruit ( Carica papaya ), is thought to replicate the action of traditional puering and bating. The protein-digesting enzyme is now used extensively in the leather industry, and follows the dehairing of the animal skin, usually with lime and other proteolytic enzymes, and the deliming of

513-535: A process for removing lime from the skins, and nothing more, and since the use of animal fæces was repulsive, sought to substitute them by inventing artificial bates. What they failed to realize, however, was that bating also acts upon the skin fibres, rendering portions of the skins soluble, bringing about the finished condition. One of the early inventions made to replicate bating was the chemical use of old lime liquors (with high levels of ammonia) neutralized with sulphuric acid . This method more nearly approximates to

570-400: 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

627-528: A vat of water and let them deteriorate for months. The mixture would then be placed over a fire to boil off the water to produce glue. A tannery may be associated with a grindery, originally a whetstone facility for sharpening knives and other sharp tools, but later could carry shoemakers ' tools and materials for sale. There are several solid and waste water treatment methodologies currently being researched, such as anaerobic digestion of solid wastes and wastewater sludge. Bating (leather) Bating

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684-430: Is a technical term used in the tanning industry to denote leather that has been treated with hen or pigeon manure, similar to puering (see puer ) where the leather has been treated with dog excrement, and which treatment, in both cases, was performed on the raw hide prior to tanning in order to render the skins, and the subsequent leather, soft and supple. Today, both practices are obsolete and have been replaced in

741-419: 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

798-403: 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

855-416: 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

912-419: 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

969-428: 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

1026-421: 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

1083-420: 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

1140-419: Is the only step in leather processing where enzymatic process cannot be substituted by chemical processes, as the process of bating gives certain desired characteristics to the finished leather. Large-scale use of microbial enzymes, following the introduction of fermentation technology, has become standard in the tanning industry. Enzymatic soaking of the raw hides has been shown to loosen the scud , initiate

1197-439: 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

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1254-461: 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

1311-504: The tannins found in the ground leaves and crushed tender stems of Acacia ( Acacia etbaica and Acacia nilotica kraussiana ), with which a bath solution was made and the raw hides inserted and left there for about two weeks, constantly stirring and changing the water after one week. In some places in Yemen, the leaves of African rue ( Peganum harmala ) were used instead of Acacia leaves. In Yemen and Ethiopia , castor-bean oil derived from

1368-455: The 12th century by Abraham ben Isaac of Narbonne (1085–1158) mentions the tanning method employed in his day, in southern France , where the treatment of the rawhide by puering was still in use and done after the hairs of the animal were removed by lime in preparation for writing a Torah scroll and the hide had once again become stiff: After taking dry [sheep]-skins whose wool had been soaked [in lime water for removal], they leave them in

1425-411: 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

1482-414: The animal hide with mineral acid. This process is thought to release traces of lime still trapped in the hide after the deliming process, in addition to removing unwanted grease, besides aiding in the subsequent tanning process by the alteration of protein. Today, in the modern tanning industry where almost all innovations have been made by substituting vegetable tanning agents with chemical agents, bating

1539-487: The animal skin to make the leather soft and supple. This step was followed by drenching , a term denoting skins that were thoroughly washed in a bath solution of bran (usually of barley or rye ), or ash bark. This process was thought to open up the fibre, and, if lime ( Ca O ) was used to remove hair before the actual bating, drenching removed excess or residual lime trapped in the leather. Early inventors who concerned themselves with tanning looked upon bating as

1596-408: 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

1653-485: 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

1710-436: 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,

1767-459: 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 ,

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1824-416: 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

1881-540: 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

1938-486: The conditions of the dung. Puering fell into disuse after Robert Hasenclever  [ de ] began producing the enzyme pancreatin on an industrial scale between 1895 and 1897. By 1907, it was used by Otto Röhm in the tannery. J.T. Wood, investigating the microbial properties of dog fæces, was able to isolate species of different bacteria, determining that aged dog fæces was more potent (hence, more efficacious) than fresh dog fæces. The bacteria that settles on

1995-409: 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

2052-516: The duration of time that it takes for it to whiten, leaving it in that state until it dries [=tanning]. They afterwards shake-off the excess gallnuts and then cut the leather. Tanners in Egypt in the 12th century and in Yemen of late made use of different methods in varying degrees, yet without the use of puering and bating, and without the use of gallnuts. Rather, after soaking and fleshing, tanners utilized

2109-447: The earliest references to puering is found in the old rabbinic Minor tractate , Kallah Rabbati (end of chapter 7): "What is the reason that dogs were privileged to have books of the Law and doorpost scripts prepared from their excrement? It is because it says [of them]: 'not a dog shall bark against any of the people of Israel' (Exo. 11:7) ." A record of primitive tanning bequeathed in

2166-425: 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

2223-434: The excrement releases, under right conditions, the principal enzyme trypsin . Primitive tanning methods differed from country to country, but the use of puering and bating was not prevalent in all of them, as tanners had moved away from their use and employed vegetable tanning which achieved nearly the same result. In western societies, modern tanning techniques tried to replicate the effect of puering and bating by using

2280-562: 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

2337-418: 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

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2394-406: 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,

2451-459: 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,

2508-406: 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,

2565-502: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Tanyard&oldid=905953322 " Categories : Disambiguation pages Place name disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Tanning (leather) Historically, vegetable based tanning used tannin , an acidic chemical compound derived from

2622-427: The opening of the fibre structure, and to render a leather product with less wrinkled grain when used at an alkaline pH of less than 10.5. In rabbit skins it improves the softness and elasticity, and increases the surface area yield of the fur by 3.3%. Bating also acts to hydrolyze casein , elastin , albumin , globulin -like proteins, and nonstructural proteins that are not essential for leather making. One of

2679-427: 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

2736-508: 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

2793-413: The tanneries with other natural proteolytic enzymes . Since early times, tanners have made use of either dog fæces , or hen and pigeon manure, in one of the early phases of leather treatment to produce a soft leather. A bath solution containing the animal extracts was made and the raw hide inserted and left there for a few days, which activated the bacteria and enzymes that reacted with the collagen in

2850-403: 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

2907-407: 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

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2964-492: 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

3021-418: 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

3078-513: The water for the duration of time needed for them to become soft [=soaking]. Afterwards, they put them inside a pit made for them, and they put therein a little dog fæces, having no prescribed quantity [= puering ], and a little salt [is added thereto], and then they seal the mouth of the pit, leaving it there for one day in summer months, and three days in winter months, no longer [than the duration of that time], so that they be not eaten up. They then remove them and check them for holes, and if there be

3135-419: 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

3192-523: 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

3249-424: 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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