Leather glossary -
Interesting facts about leather.

The term "aniline" in leather refers to the transparent colouring with dyes that do not cover the visible hair holes or the surface and do not cover the natural grain pattern / pore pattern or the natural surface of the leather.

Attempts to replace the use of the term "aniline" for leather with, for example, "natural leather" in order to avoid confusion with the blood poison aniline have failed due to the term being firmly established as a synonym for transparent colouring in the vernacular. As a result, the term aniline or aniline leather is still a traditionally well-established technical term both in the German language and in corresponding translations into other languages

These are leathers coloured with soluble dyes after the tanning processes as part of the wet finishing process. The dyes can be absorbed and bound by the leather fibre by placing the leather in the dye liquor (e.g. in a barrel) or by applying a more concentrated dye liquor to the surface(s) - by head dyeing. The grain surface of the leather is exposed and has the most natural appearance. However, this also means that there may be changes on the grain surface of the leather (natural features and damage) as well as certain slight irregularities in the surface colour (in both natural and aniline leathers).

Nappa leather refers to all types of leather for various purposes that are softer and more supple than their traditional leather type for the respective purpose. Nappa leather is therefore found in different basic hardnesses or basic softnesses such as upper leather nappa, furniture leather nappa and upholstery leather nappa, clothing leather nappa and glove leather nappa as the most important representatives of nappa leather.

A special and unmistakable characteristic of these different types of soft nappa leather is their grain integrity, i.e. the full grain and completeness of the grain or natural pores. The alteration, decimation or roughening of the grain/natural pores through various measures is not permitted for the designation as Nappa leather. The designation nappa leather has no influence on the amount of pigmentation (restriction or upper limit is defined in RAL 060-A2, „Abgrenzung des Begriffes Leder gegenüber anderen Materialien, Bezeichnungsvorschriften“) and the transparency of the respective nappa leather. The transparency, i.e. the visibility of the natural pores/grain, is regulated by the additional designation aniline, semi-aniline and pigmented leather and allows the additional designation nappa in all cases.

Antique leather is a strong leather with a strongly pronounced grain which is usually produced in two colours (in that the raised areas are dyed differently from the deeper areas). Antique leather imitates the old types of leather from the Middle Ages and is used as furniture leather / upholstery for so-called "club chairs" or for the interior fittings of carriages.

Only rarely is antique leather specially prepared during the tanning process. If this is done, the aim is to give the leather the contracted, so-called "wild grain" that tanners used to rightly fear from ordinary types of leather.

In order to achieve unusual and extravagant effects, colouring is carried out using various tricks. The ground is always dyed in a different colour from that of the raised areas, the wrinkles or the artificial grain.

Technical leathers also include the large group of labour protection article leathers. These leathers, also known as WPA leathers, are mainly used for the production of aprons, gloves, hand leather, as well as protective clothing for the head, hands and knees, etc. The raw material chosen for this is cowhide or strong split leather, which is produced using chrome tanning because of its particular heat resistance. They should be well washed out, lightly greased and only have a low tensile strength. It is also important to ensure that no skin-irritating substances in water- or sweat-soluble form are present in the leather. Despite a low fat content, such leathers should be soft and supple throughout, and provide adequate protection against the effects of moisture, high temperatures, acids and alkalis, etc. Grant.

Bandage leather for orthopaedic purposes, for straps, for prosthesis edgings, a sufficiently supple leather, must not shrink after repeated washing. Bandage leather is usually produced in combination tanning.

The term garment leather covers a range of special leathers that are used to make leather coats, jackets, trousers and costumes. They must be softer to the touch than shoe uppers, as water-repellent as possible, breathable and sufficiently permeable to air. Particular elasticity is required of the applied finishing colour, as this type of leather is subject to high bending and buckling stresses; furthermore, the finishing must not break prematurely or flake off. Such leather should also be sufficiently resistant to dry and wet rubbing and to the effects of perspiration.

Leather must be labelled as coated leather if an applied layer has a thickness of more than 0.15 mm. The same applies if more than one third of the total thickness of the material is not leather.

The type of layer on the leather is not specified and can consist of a wide variety of materials. Pigments and binding agents, foils, foams etc. are often used for the coating.

„Blankleder“ is a vegetable-tanned, moderately greased cowhide leather with a thickness of 2.5 mm or more, which has good stability and good strength properties with sufficient elasticity and flexibility. This type of leather is used for the production of strong saddlery, saddles, belts, bags, satchels, briefcases, etc. Well-positioned cow and calf inner hides, as well as lighter and medium bull hides, are used to produce this type of leather.

Chrome calfskins are the main type of all better shoe uppers of lower thickness. Box calf leather is produced in a wide variety of sizes and thicknesses up to the transition to cow box leather, in black and coloured finishes, smooth or crinkled, shiny or matt. Box calf leather is normally no more than 1.2 mm thick. In addition to the full, supple feel due to moderate fatliquoring, a certain degree of stability and good tensile strength, the tight, fine and beautiful grain is the essential characteristic of box calf leather.

Due to its special function in the construction of footwear, insole leather must have a corresponding structural strength of its fibre structure as well as sufficient toughness and strong flexibility. In contrast to sole leather, it should be able to absorb certain amounts of moisture, be stable against perspiration with its de-tanning effect and not contain large amounts of substances that can be washed out. For its production, halves, sides and necks are tanned using tan tanning or split tanning or combination tanning

For binding books. The most important processing requirements for the leather properties here are good softness with sufficient dimensional stability. The leather must be able to be firmly applied to the binding (formerly beechwood boards), which is usually made of cardboard, and be flexible in the spine. The leather must not stretch out like rubber, especially during the preparatory work of skiving. It must also be possible to work the bead-shaped frets out of the leather on the spine. As these are usually more valuable books, a long shelf life is a prerequisite.

Chevreaux leather, chrome-tanned, lightly greased goatskin upper leather, in thicknesses of 0.6 - 1.2 mm, is the finest shoe upper leather and is made from light goatskins and kid skins which were originally produced using the two-bath chrome tanning process. The most important thing in the production process is to obtain a pure, firm grain. Chevreaux leather is greased in the same way as box calf leather, but is dyed more intensively. To obtain a leather with full handle, chevreaux leather is often treated with gambir after chrome tanning. Chevreaux leathers are finished in the same way as box calf leathers, except that the grain must be completely smooth.

Crust leather (bark leather, en croute) in the true sense of the word arose from the endeavour to process as many raw materials as possible domestically to a state that is practically unchanged even after a long storage and shipping period and that allows further processing. In the case of leathers that are traded under the designation crust leather, a basic distinction must be made between crust leathers that have only undergone vegetable tanning and chrome crust leathers that have been dried after chrome tanning in the ready-to-wet state, or that have been additionally retanned until they are ready to finish, whereby a further distinction must be made between crust natural (undyed) = bark and crust drum dyed. In addition to chemical processing in a water workshop and tanning, crust leathers may have undergone the following work during production:

1. dehairing, fleshing, painting in the water workshop;
2. washing, dewatering (pressing, withering), stretching, bleaching and drying;
3. greasing, provided that a minimum grease content is not exceeded.

All additional work that opens up the possibility of direct further processing, e.g. sanding to achieve a velour-like appearance or thickness adjustment, etc., is not permitted. The leathers should be in a condition that clearly indicates that they are not directly usable, as otherwise they may be classified in other tariff groups.

Russet Upper Leatheris also a heavily greased upper leather that is used especially for work shoes and heavy-duty footwear.

Hides weighing around 20 kg are tanned using purely vegetable methods and made supple by greasing in a hot-air barrel. Both the grain side and the flesh side can be worn on the outside, which is particularly visible on mountain and hiking boots. Russet Upper Leather is also processed into bags and leather goods.

The production of fine leather from calf, sheep and goat skins as well as from the skins of numerous sea animals and, rarely, lizard, snake and crocodile skins and bird skins in various shades of colour takes account of their extraordinary diversity of use.

These leathers are also categorised as technical leathers. They are made from suede, sheep and goat skins using chamois or new chamois tanning, whereby the latter process has the advantage of greater alkali resistance.

Lining leather is one of the types of leather required for shoe construction. This material, which is used in particular for the interior, should above all fulfil the requirements of particular softness and suppleness; it is also required to be sweat-resistant and, finally, it must be well washed out, as otherwise, if soluble components are present, they will diffuse into the upper leather after the shoe has become wet and form a rash there. Vegetable-tanned, chrome-grey, combined chrome-vegetable-tanned cowhide of the appropriate thickness, calfskin, goatskin, sheepskin and pigskin can be used as lining leather in addition to all possible split leathers. In addition to softness and suppleness, a lining leather is required to have sufficient absorbency for the moist vapours of the foot and sufficient sweat resistance.

Lighter cowhides of appropriate thickness, calfskin, goatskin and sheepskin can be used to make the lining leather. As a rule, these leathers used to be vegetable tanned, but now a combined chrome-vegetable tanning or pure chrome tanning is preferred.

They are finished naturally, sanded like velour or dyed and given a light application of opaque colour. In general, leathers that can no longer be used for higher-value applications are processed for lining leather purposes.

Harness leather is similar in its overall composition to a more heavily greased uncoated leather, which is required to be more supple, elastic and highly tear-resistant; it should also be weather-resistant and free from skin-irritating substances. The production process is similar to that of uncoated leather, with the difference that harness leather is usually given a fat content of 15 - 25% by warm greasing in a barrel or even by light baking, which on the one hand increases its resistance to the alkaline vapours of the stables and on the other hand increases its suppleness and tear resistance. In addition to tallow, tran, degras, stearin and paraffin, special types of wax are also used as fatty substances. Harness leather is produced natural or blackened, only rarely coloured. Chrome-coloured harness leather is also used. Certain harness leathers, such as stable halter leather with particularly high requirements for tear resistance, are tanned using chrome yarn.

Glove leather can be made from a wide variety of raw materials and in a wide variety of tanning methods. This type of leather is always a thin, supple and supple, white or coloured leather with sufficient tensile strength and tear resistance. The suppleness and softness will only decrease if the glove leathers are produced for technical applications. (German armed forces, police, fire brigade).

They are also categorised as clothing leathers. However, they are speciality leathers in that special requirements are placed on these leathers. As a common characteristic, they must not contain any substances that irritate the skin. The pH value must not be below 4.0 and the content of free fatty acids is limited to a maximum of 2.0 %. Goat, sheep or hair sheep skins are used as raw materials. The tanning of these leathers is preferably purely vegetable. Hat sweat leather can also be vegetable/chrome tanned in combination. Helmet sweat leather is used in protective helmets. They must have sufficient absorbency to absorb perspiration. Natural leathers are used without any finishing.

Aldehyde tanning, or tanning with glutaraldehyde (glutardialdehyde), is usually carried out during leather production on the still untanned pelt. The quantities of glutardialdehyde normally used and the pH value control allow almost complete consumption and reaction of the astringent glutardialdehyde. Special migration behaviour, residual aldehyde etc., incompatibility with leather tanned in this way are not known. Special features of this tanning process, which is usually carried out in combination with other vegetable or mineral tanning agents, are the special sweat fastness and washability of the very stable tanning process. This is why the sole tanning of sheepskins with glutardialdehyde is referred to as "medical tanning", "washable tanning", "hospital skin tanning", "yellow tanning", "Relugan tanning", as the special washability and insensitivity to the skin has particularly favourable effects. Hence its use as a washable bedskin or couch skin, cleaning and polishing skin.

Leather that has been sanded from the grain side / hair side so that the natural grain pattern is still visible, but a velvety-soft, finely sanded, short-fibre surface is created. The natural grain pattern of nubuck leather is the remains of the hair holes / pores that allow the grain side to be clearly identified. Nubuck leather is sanded from the grain side (hair side) and not sanded away, whereby the hair pores must not be completely removed and the natural grain/poring (possibly with a thread counter) must remain recognisable.

Special features of nubuck leather are the special velvety feel and the writing effect. Nubuck leather can be made from almost all animal skins. Due to the histological differences in animal skins, certain animal skins are better suited to suede production than others. The difference can be seen particularly in the fibre length/grindability of the grain side. The shorter the fibre cut, the higher the perceived quality of the nubuck leather and the more pronounced the typical nubuck leather writing effect.

These leathers are used for the manufacture of footwear uppers, linings or insole and sole leather in the shoe bottom area, but also for the lining of prostheses or as lining leather with direct body contact. The quality guidelines for orthopaedic leathers describe the special requirements of these leathers, e.g. in terms of pH value, total ash, extractable substances, total leaching loss, harmful substances, bulk density, tensile strength, elongation at break, tear propagation resistance and the bending angle of the mandrel bending test as well as water absorption, water vapour permeability index and fatigue bending strength. For orthopaedic strap and glove leather, sweat resistance and colour fastness are also required. These special requirements result from possible direct body contact under the influence of moisture or sweat. This moisture contamination with possible wash-out losses can be problematic for sensitive, irritated or sore skin and must be limited by appropriate leather technology measures. In particular, vegetable or vegetable/synthetic and chamois tanned leathers can be used with regard to the requirements stipulated in the quality guidelines, as well as the generally recognised good foot climate conditions (wearer hygiene), skin compatibility and individual dimensional stability. The latter ensures that the foot moulds quickly without pressure points. High water vapour permeability should guarantee that the foot or covered body parts are kept dry and prevent moisture contamination. In the case of chamois leathers, the high water absorption and special compressibility of the tanned leather matrix, combined with good skin compatibility, are advantageous.

Peccary leathers are chrometanned, soft, washable glove leathers with pronounced papillae, made from the skin of the South American umbilical pig Peccary or capybara Carpincho.

Also belonging to this type of leather, it differs from transparent leather in that it is filled with white pigments to remove the transparency. Parchment is used as grain leather for bookbinding purposes.

Even in early antiquity, dehaired and dried sheep and goat skins were used as a material for writing. In the small Asian city of Pergamon, these skins were processed in large quantities for this purpose, so that they formed the city's most important branch of trade, from which the name "parchment" is derived. Parchment became very important in the Middle Ages, and in France, for example, its production was supervised by the University of Paris. Even today, important documents whose durability is as indefinite as possible (e.g. diplomas, addresses, memorials, documents for headstones and keystones) are still written on parchment. In the Middle Ages, parchment was also often used for book bindings, although this use is now only rarely considered.

Timpani and drum skins as well as sieve bottoms are also made from parchment.
br>All types of hides and skins can be processed into parchment, but writing parchment is usually made from the skins of calves, deer and stags, lambs and kids, while parchment for book bindings is often made from pig skins.

Frame leather are soft-tanned, moderately greased lower leathers (with approx. 7 - 8 % fat), which are cut into approx. 1.5 - 2.0 cm wide straps when ready-made and as such serve as a connection between the insole, lining leather, upper and bottom in welted footwear. It is a leather with a dense structure that is vegetable-tanned from cowhides weighing up to 25 kg, moderately greased and finally split to a thickness that is as uniform as possible for use.

This generic term refers to all types of leather with a buffed side.

This includes suede leather, nubuck leather and suede leather. It is initially irrelevant whether the suede leather is made from grain leather or split leather and from different hides / animals. In the production of suede leather, the flesh side (the side facing the animal's body) is sanded to a suede-like finish. The result is a fibrous surface. Nubuck leather is sanded from the grain side (hair side) and not sanded away, whereby the hair pores must not be completely removed and the natural grain/poring must remain recognisable.

Leather with a more or less strongly contracted surface with different elevations of the grain crests, whose reticular layer is tanned quickly and massively by particularly astringent tanning agents and a loss of surface area is caused by this cross-linking on the flesh side and the fibres coming closer together.

Sole leather is generally understood to be a relatively hard, less flexible leather, recognisable by its sour smell and the peculiar grey coating (mud) caused by ellagic acid escaping from the surface of the leather. This leather is mainly used for heavy, high-quality, hard-wearing footwear, including military footwear and for certain repairs to such shoes.

The raw material used is predominantly heavy cowhides, i.e. cowhides and ox hides that are evenly spread over the entire surface. This manufacturing process is designed to be extremely gentle on the fibre structure; the hardness of the leather is determined by the type of tanning preparation, a very short and gentle liming process, occasional hair loosening through sweating and only superficial deliming. The pelt is then first given a six-stage colouring process, then passes through one or two sinks for further pre-tanning, and the tanning is then completed in at least three sinks after a period of three to four months. Oak bark, usually mixed with spruce bark, as well as mimosa and valonea, is mainly used as a scattering material; the offsets are impregnated with thin tanning broths; the tanning time is 12-18 months, depending on the thickness of the hide. Finally, the leathers undergo a very simple finishing process: after coming out of the pit, they are dried, brushed to remove the adhering tan and then rolled in a single machine operation. The leathers produced using this process are referred to as "pure or old pit tanned leather".

Split leather is the middle and lower parts of the hide obtained by splitting; however, grain split leather consists exclusively of grain substance without coarse leather fibres.

Split upper leather is of particular importance in practical use as shoe upper leather. In the production of large-area leathers such as cowhide box, vachettes, etc., usable flesh splits are obtained, which can be tanned with chrome or vegetable tanning if they are sufficiently strong and, after appropriate treatment by dyeing, priming with finishes, topcoat colouring, possibly also by grain pressing, can be processed into well usable upper leather.

The treatment of pelts with fish and other sea animal oils (tranes) is one of the oldest tanning methods. The tans used are rolled into the pelts and bound in the fry via intermediate aldehyde stages. The leathers produced in this way are very soft and quick, which is further enhanced by the fact that the grain is usually shed from the pelts (of deerskins) before tanning or, in the case of sheepskins, split off. The yellow chamois leathers (suede, chamois leather) show a very strong water absorption capacity, old chamois leathers are only tanned with tran, while new chamois leathers have a combination tanning (usually with an aldehyde pre-tanning and the tran tanning).

These types of leather are characterised by vegetable-synthetic tanning, which ensures good dimensional stability and the special stability required for some applications. The leather intended for the manufacture of such leather goods is mainly made from light cow hides, but also from split bull hides. The preparatory work, such as that in the water workshop as well as the tanning and colouring (usually purely aniline) and the finishing, is similar to that of untreated leather. The leathers themselves are finished smooth or embossed.

Vachette leather is a thin, large, supple and non-slip, only moderately greased cowhide of about 1 - 2.0 mm thickness, obtained from thicker cowhide by splitting, which is used as upholstery leather for furniture and cars, soft-top leather, framing leather, etc. etc. It is produced almost exclusively in vegetable tanning, only rarely in chrome tanning (then chrome vachettes). Large bull hides are used as raw material, more rarely flat cow hides.

In the production of suede leather, the flesh side (the side facing the animal's body) is sanded to a suede-like finish. The result is a fibrous surface. The special features of suede are its velvety feel and the writing effect. Suede can be produced from almost all animal skins. Due to the histological differences in animal skin, certain animal skins are better suited to suede production than others. The difference can be seen particularly in the fibre length/grindability of the fibre. The shorter the fibre cut, the higher the perceived quality of the suede leather and the more pronounced the writing effect typical of suede leather.

Vintage leather is when the special look promises a "used look". In leather, this is often associated with a silky lustre and a crumpled appearance.

These leathers are always fully preserved on the grain side and the thickness or substance of the grain has not been superficially altered or rejuvenated. Sanding or buffing or other processes that change the substance by removing it are not permitted.

Waterproof are cowhide upper leathers, usually chrome or chrome-vegetable tanned, which are made largely impermeable to water through a special fatliquoring or hydrophobisation process. They are mainly used as upper leather for sports and hiking boots, especially for heavy utility footwear. Medium-weight cowhide, cowhide or oxhide is used as the raw material.

Wet Blue refers to moist chrome-tanned leather. In this phase, the leather is fully tanned but neither dried, dyed through nor finished. The bluish colour is produced by the chrome tanning agent, which is blue and is contained in the leather after tanning.

Wet Blue must be stored at a moisture content of approx. 60%. It can then be kept for up to 6 months and is traded worldwide. The transport of Wet Blue as a traded semi-finished product requires treatment with preservatives (biocides) in order to prevent microbial infestation during the sometimes long transport and storage times. Only biocides that are largely toxicologically safe and authorised in accordance with the EU Biocidal Products Regulation 528/2012 are currently used as preservatives. If Wet Blue becomes too dry, it can become stained or have negative properties in the subsequent work steps, which reduces the processing possibilities of Wet Blue.

Wet-brown is a vegetable-tanned or vegetable-synthetic tanned leather (at least 1/3 vegetable tanning agent content) in a wet state immediately after tanning. The water content is usually reduced by mechanical processes such as (stretching, wilting) Wet brown is a semi-finished product and must undergo further process steps.

Leather tanned with olive leaf extract. Olive leaf extract tanning agent can be used as a pre-tanning agent or main tanning agent. The semi-finished wet leather -wet-green®- is recognisable by its own light yellow-green colour. Leathers tanned with olive leaf extract can be produced in all qualities and colours. Olive leaf tanning agent is obtained from olive leaves and is considered to be particularly sustainable. The patent holder is the company wet-green GmbH. The technical applicability and leather technology principles for the application and use of olive leaf extracts were developed by the Lederinstitut Gerberschule Reutlingen in co-operation with the company N-Zyme BioTec GmbH.

Wet white refers to moist, synthetically tanned leather. In this phase, the leather is tanned, but neither dried nor dyed through and not yet finished.