A process of tanning with alum, used in combination with salt, egg yolk and other substances. A major tannage for gloves in history, only used infrequently today.
Leather that retains its colour only from dyestuffs rather than from pigment, and as a consequence looks more natural. Often considered the highest quality material. Its colour is just from the dye process. Aniline leathers are literally “naked” allowing the natural beauty of the grain to show through. All skins will have some faults, even aniline leathers. Slight scratches or surface marks are part of what makes up a natural material and should be regarded as such. They will not affect the performance of the leather.
Bark tanned pickled sheepskins
The process prior to tanning proper where the fibres of a hide or skin that have been plumped or swollen by liming are reduced and softened, thus assuring pliability in the product. The word is a form of “abate” in the sense of reduce.
The area of the tannery where the unhairing and liming processes are carried out. Before modern machinery the processes of fleshing, scudding and others were carried out over specially designed wooden beams using curved two handled knives with sharp or blunted edge according to the operation. Hence the name. Beamhouses in Europe in the Middle Ages were mostly sited on the riverside, and the skins cleaned and softened by hanging in the water. Often the local name for this department is a derivation for the local word for “river”.
Sandpapering the leather with sandpaper or emery paper for various reasons such as the creation of a suede like nap on suede, a nubuck finish on grain, or for the preparation of corrected grain leather. Sometimes done on the flesh side to tidy up its appearance.
A wrongly named hair sheep. When the Portuguese first went to Brazil they mistook the indigenous hairsheep for goats and called them cabrettas (kids). The skins were exported to the USA by the Booth Line (part of the Booth Tanning Group) and the name cabretta stayed with them. Now all hairsheep skins have taken the generic name cabretta. Much used in footwear leather and sport glove leather.
Sheepskin from South Africa, which has been much, used for gloving. Essentially from the Cape and the Port Elisabeth areas.
Where skins are not cut down the belly, but merely pulled from the animal
A soft leather originally made from the skins of the Alpine antelope known as the chamois but at the present time from the fleshers of sheepskins. Certain grades used to be used in gloves and fancy articles but the staple employment is for cleaning and polishing, primarily automobiles. Chamois is characterised by an ability to absorb at least three times its own weight of water.
Introduced in the USA as the main tannage for glove leather about 1890. Became common in Europe for glove leather by 1930, and now is used to tan over 95% of all glove leather. There is some evidence that the percentage of chrome tanning in glove leather might reduce over the next ten years, as has happened with motorcar upholstery.
When leather is dried after retanning, dyeing and fatliquoring the fibres tend to stick together and the leather is hard. The fibres are separated and the leather softened by staking. Staking is best done at about 18% humidity and so a little humidity has to be put into the dry leather. This is most commonly done by a water spray and then piling the leather long enough for the moisture to even out. Adjusting the moisture content before staking in this way is called conditioning. Used to be done by placing the skins in piles of damp sawdust.
Developed in Spain in the 8th century, and named after the town of Cordoba. Made from the skin of the mouflon (Ovis Musimom). This hair sheep now only survives in Corsica and Sardinia. It was tanned with sumac or alum. Best brilliant scarlet type was tawed with alum and dyed with kermes. The term subsequently came to describe many types of leather and is often confused or overlaps with “Spanish tannage”.
This type of leather has the surface buffed away – taking with it any imperfections. A glossy appearance is created by applying a smooth coating of finish colour. Although a less expensive type of leather, corrected grain nevertheless requires skilled manufacturing to ensure consistency and durability. Not much used in fine gloves although some is taken into work gloves.
Leather dried after tanning. Since chrome leather dried immediately after tannage will go hard, change charges and become difficult to rewet, this drying normally takes place after a basic retanning and fatliquoring. Leather is frequently traded world wide in this state, although tanners normally prefer to buy wet blue or pickle which gives them more flexibility of processing.
A process preparatory to tanning proper to reduce the swollen and rigid fibres of a hide or skin after liming.
The inner flesh split of a wool sheep tanned with formaldehyde process to make gloving leather.
For many years dogskins were used for gloving, and still are in China. They are very thin and strong. The name has also been used for heavy weight sheepskins used for hunting and hawking gloves.
A vegetable and alum tannage developed by James Kent in Gloversville, New York, in 1881 to compete with the expensive kid tannage for gloves. Used hair sheep. Dongola is a town in the Sudan, and there is a breed of hair sheep named after it. “Dongola leather was invented in the time of the Egyptian War, when Dongola was much in the public mind, hence its fancy name”
“Dongola, strictly speaking, is alum, salt, and gambier only, used together in one solution. Dongola is especially applied to glazed and dull kid. For full dongola the process is commenced in very weak gambier liquor, with the full proportion of alum and salt, and the gambier is gradually strengthened.” Although many Dongola gloves were made the leather was in fact better for footwear using kidskins and kangaroo. It continued to be produced in the UK using calf skins for footwear until the 1930s.
A process for reducing the plumped fibres of a hide or skin. It accomplishes approximately the same purpose as bating and basically in the same way – that is, through soaking in a fermenting solution. Some authorities, however, restrict the term bating to the process using ferments of manures and the term drenching to that using damp sawdust, bran, middlings, or a solution of lactic acid or some other chemical having a similar action.
The collective term for the rotary vessel in which many processes of tanning are now carried out. First used by tanners in Mechelen, Belgium in the 1600s to help speed up the tanning of leather for wall hangings. Tanners legally opposed this innovation as they said true leather needed nine months in pits. The drums were turned by foot. Drums became common only towards the end of the 19th century. This is one of the best documents struggles between the guilds and I beleive the legal batlle took thirty years and all the papers still exist in the Mechelen archives.
Using fats and oils in appropriate mixes to lubricate and soften the fibre structure of leather, giving the leather the required softness for its eventual end use.
The flesh piece from a thick woolly sheep which has been split into two layers. Used to make chamois. The grain is made into a skiver. Sometimes for cost and easy maintenance the material is part tanned and then split. The grain is then called a pliver. The flesh created in this latter way will not make true chamois.
Small pieces of leather used to make the sides of the fingers in glovemaking. Sometimes called gussets.
The process of removing the grain of a skin by exposure to a strong lime liquor over an exceptionally long period, sometimes as much as eight weeks. Such skins, after tanning are finished on the fine fibres under the grain. This is the method used in the manufacture of mocha glove leather and of certain classes of buckskin.
Full grain leather
Leather whose grain has not been sandpapered or buffed to hide defects. Full grain is produced from the top side of the leather i.e. the outside of the skin. The surface will normally be smooth and polishable.
An old term for a glover. Perhaps someone who made strong working gauntlets from vegetable tanned leather for such activities as hawking, metal workers, soldiers and farmers. But this has not been researched.
A self-explanatory term which, however, covers two rather distinct classes: the leather going into utilitarian or work-gloves and made of a variety of hides and skins, of which the most important are horsehides, cattle hide splits, calfskins and pigskins; and the leather going into dress-gloves, including those for street, riding, driving, and sports wear. The latter is tanned predominately from sheep and lambskins; but there is a considerable item made of deerskin and a small one of pigskin, while an important item for the highest grades of women’s fine gloves is tanned in a few countries of Europe from kidskins. (Old definition)
The surface of a piece of leather, the appearance of which is characteristic for different animals, being mostly dependent on the distribution and size of hairs. The hair follicles are left visible after the hair is removed and there pattern gives leather of different types a distinct look.
A term distinguishing sole leather, belting leather, and harness leather proper from other classes which are referred to collectively as light leathers.
Raw material for leather from a larger animal such as a cow, steer, ox or buffalo. Pelts from sheep and goats etc are classed as skins.
In the hair; in the wool; in the raw
A group of more or less equivalent terms used to describe stock that has not yet undergone any of the processes of leather manufacture.
In the rough; in the crust; in the white; in the blue
A group of approximately equivalent terms used to describe stock, which has been tanned, but not finished. In the rough or rough tanned is most commonly applied to vegetable tanned cattle hide leathers; in the crust and in the white to vegetable, alum or formaldehyde tanned sheepskins and lambskins; and in the blue to chrome tanned skins particularly goatskins. The use of the term in the white needs to be distinguished from that mentioned in the following definition See also Wet White and Wet Blue.
In the white; in the pickle
Two roughly equivalent terms used to describe stock, which has undergone the processes preliminary to tanning, but has not been actually tanned. Historically in the pickle is restricted to sheepskins and lambskins; in the white, in this sense, is used for practically all other classes of hides and skins.
A jasmine scent which was usually made up in the form of “jessamy butter” so it could be put onto the inside of the glove.
Laminating leather to other materials is a means of creating a product that has unique properties. Selecting different laminates with their own special properties can vary the properties. E.g. Elastic, or fire resistant materials.
For the avoidance of all ambiguities and doubts, which may and do grow upon the definition and interpretation of this word leather, it is enacted, and declared by these presents, that the hides and skins of ox, steer, bull, cow, calf, deer, red and fallow, goats and sheep being tanned or tawed, and every salt hide is, shall be, and ever hath been reputed and taken for leather. Act of Parliament. UK year 1604
Leather for clothing, gloving and shoe uppers mostly chrome tanned.
Chicken skin gloves from Limerick in Ireland. Some were actually made of chicken skin, but most were from the skins of unborn calves.
A process preliminary to tanning, which serves one or both of two purposes: to loosen the hair or wool on a hide or skin, preparatory to dehairing; and to plump or swell the fibres as of the processes necessary to prepare the substance for the action of the tan liquors. Liming is always required for the latter of these purposes.
Name given to hairsheep used for dress glove leather. Most commonly used by New York dress glove companies.
Pre-treating leather with any substance save acid or alkali which substantially alters its affinity for dyestuffs.
Finished leather with a pronounced grain, a term usually applied to goatskins. The process seems to have started in the Babylon area and been perfected in North Africa before being transferred into Europe via Spain.
mousquetaire (musketeer) gloves
“In 1870, the famous French actress, Sarah Bernhardt, began to wear long gloves in soft leather that folded up the sleeves. These gloves were a fashion development from the gloves worn by musketeers who had for decades protected the French kings. Originally, duelling gloves were made as singles and they went over the sleeve up the arm to offer a little extra protection. For Sarah Bernhardt, they were made tighter and apparently they flattered her arms and soon became highly fashionable under the name ‘mousquetaire’. She took the style to the USA and it has remained important since then.”
— Gloves and Glove-making (Shire Library Book 812) by Mike Redwood
A cheap sheep or lambskin glove leather, made with an alum or combination tannage, and usually given a dull grain finish. The name is taken from the town of Napa in California.
Nubuck is produced from full grain leathers. The grain is abraded away to create a light surface nap. This can be adjusted to be very fine, or a longer, softer effect can be produced.
Now mostly called chamoising and used to make chamois leather from the flesh side of woolly sheep. Was an important tannage for other hides and skins in the Middle Ages, especially deer. Much used under chain mail to keep the soldier warm and prevent chaffing. The tannage is based on oxidising oils inside the skin.
Oiled and Waxed
Oils and waxes are coated onto the surface of the leather to produce a tacky finish that gives improved grip. They can be used in many sports, e.g. Horse riding, and American football gloves.
A name applied to certain types of machinery with rotating arms, which are used in various tanning operations for agitating hides or skins in process. Use more water than drums, allowing larger floats and consequently gentler action. Mostly used in the soaking and liming areas.
A process for loosening hair or wool (usually the latter) which is employed with skins whose protective covering is so valuable as to make it desirable to avoid injuring it by soaking in a lime liquor. The process is carried out by painting the flesh side of a skin with a depilatory substance, containing sodium sulphide or arsenic. Nowadays this is the usual method with sheepskins bearing the higher grades of wool. Before it was invented, such skins were usually dehaired by sweating.
This word means, strictly speaking, any kind of skin (Latin pellis, related to the German felle, a skin, and the English word fell, now preserved only in fellmonger). The word is somewhat loosely used in the leather industry, but its only common applications nowadays are to sheepskins in two or three slightly differing senses: to the skin proper, to distinguish it from the wool that grows on it; to dewooled sheepskins, as a pickled pelt or a fellmongered; or in some countries to a woolskin bearing the shortest recognised staple.
A preliminary process for preparing hides and skins for tanning, largely by adjusting the pH with acid and controlling the swelling with salt. It is also use as stable way of holding material, after unhairing, for transport between plants and countries and for trading.
Pigmented leathers have a light surface spray of colour added at the final stage. This produces a uniform appearance, good for more formal shoes or leather goods. Not normally used for glove leather although some of the leather in the Isotoner dress gloves is pigmented.
In 1770 the three lines on the back of the glove evolved from previous embroidered looks into a construction and fit feature called pointing
Printed leathers can have any type of pattern/design placed onto the surface. The designs are embossed onto the leather surface under pressure and add to the character of the material; the structure of the leather is not affected.
Small leather gussets sometimes fitted at the base of the fingers and the thumb to allow more flexibility of movement.
Two directional non-elastic stretch. A re-orientation of the fibres in a skin. Important in glove leather for purposes of fit. Below 25% and above 90% extension gives poor fit, 40% is normally taken as the target.
A process subsequent to the main tannage when the character of the leather is adjusted by the addition of further alternate types of tanning material. Thus synthetic or vegetable tans may be added to chrome leather to adjust certain characteristics.
The mechanical extraction of moisture from leather after a processing stage. Most normally done on wet blue after chrome tanning, using a machine that carries the leather through felts.
A film or deposit of waste matter appearing on the surface of leather in process after certain operations, esp. bating.
One of the preliminary processes preparatory to tanning. After bating or drenching the excess fermenting materials, together with dirt, fatty matter, hair follicles, short hairs, and glandular tissue are worked out of the hide or skin. Mostly done by hand using a blunt two-handed knife over a curved beam. Can be done by machine.
This mechanical process is used at various stages in the finishing of leather to counteract the shrinking and stiffening resulting form the processes that have gone before. Most common after retanning, fatliquoring and dyeing. Normally done by machine using a knifed cylinder with blunted blades. Some modern machines combine sammying and setting and some incorporate a heated roller to help set the grain in a smooth tight configuration. Striking out is a similar process for heavy, vegetable tanned leather.
Raw material for leather from smaller animals, such as goat, sheep, most deer, fish, birds, snakes etc. Hides come from larger animals such as cattle and buffalo. Light gloves will be made from skins such as sheep and goat, while heavier gloves will come from cattle. There is a lot of imprecision in this definition as the term “skin” and “hide” often overlaps and a heavy goatskins from an older animal might be better in some circumstances at managing abrasion in the wet than a similar thickness of cattle hide, while the same skin would make a poor fashion glove compared to a younger thin cattle hide.
“N glove ever exceeded in beauty the Limerick. Those made at Limerick were of the most exquisite texture, and were manufactured principally from ‘morts’ and ‘slinks’, the skin of the abortive or very young calf, lamb or kid. Some of these gloves were so beautifully fine that they have been enclosed inside a walnut shell” from History of the Glove Trade, William Hull, 1834. This was quoted by Liza Foley in her excellent article in Costume, vol. 48, no. 2, 2014 “‘An Entirely Fictitious Importance’? Reconsidering the Significance of the Irish Glove Trade: A Study of Limerick Gloves, 1778–1840″
Slink skins are the skins of unborn animals. In the USA the term “slunk” appears to have been more common and refer more to calfskins albeit US tanning texts simply say: the skin of an unborn or prematurely born animal.” In the 21st century glove trade the term slink is most often used in relation to New Zealand sheep where the large size of the flocks mean that despite modern husbandry there is still a sizeable number of accidental deaths and the skins are collected and tanned, but I think are not collected systematically and quickly enough to be of good enough for the grain to be used. So they are processes with the wool on and often used for glove lining, as opposed to the very young lambs of France or the slinks (sometimes called morts) from Ireland which are thought to have been mostly calf, with some sheep and goat where it is the perfect grain that was treasured.
The other area is in Russia and the Caucasus are including some of the “Stans” such as Afghanistan where the skins are used more for fur “Astrakhan” or “Persian Lamb”, the husbandry methods are less modern (possibly barbaric) and the leather and the wider leather glove industry is very concerned about the situation.
Alexander Watt wrote in LEATHER MANUFACTURE, A PRACTICAL HANDBOOK, TANNING, CURRYING, AND CHROME, LEATHER DRESSING, New York 1906: “The kid skins of France from which the famous “French kid” are made have gloves always been held in high estimation, as also are those of Ireland. After the animal begins to feed upon herbage, the skin loses in delicacy of texture, and therefore becomes unsuited for the finest gloves. There can be no doubt whatever that from the time the young animal ceases to derive its sustenance from the mother, and feeds upon vegetable substances, a greater degree of solidity and firmness of texture is acquired by the skin, as also by all other parts of the body, and as a consequence the elasticity and extreme fineness “and delicacy in texture of the skin” When he discusses alum tanning he says “The skins which are subjected to the operations of tawing, or alum-dressing, are those of the kid, the calf, the lamb, and the sheep, the first being employed to produce the well-known kid leather, from which the finest sorts of gloves and uppers of ladies’ shoes and boots are made. Lamb skins, when prepared by the processes we are about to describe, form an imitation kid leather, from which the kinds of ” kid ” are made. cheaper gloves
Kid Skins… are of very small size, and have the hair on. For leather to be employed for the finest quality of gloves, the skins are obtained from the young goats before they leave the mother to feed on herbage.”
This was very much the case in Millau which had glove industry based on unwanted lambs from the nearby town of Roquefort where the cheese has been famous from ancient Roman times.
With cattle the term “grasser” has been used and small goats sometimes “suckling” and “springer”. In goats for fashion gloves skins which weight less that 30KG per 100 skins when air dried (in the raw state) are looked for. Arnold’s Hides and Skins from 1920 discusses “foetal, stillborn and kindred skins” saying that added to the skins that come from foetal or stillborn animals should be those slaughtered or dying very soon after birth. “in the aggregate such skins are more numerous than might be supposed. They differ from other immature stock chiefly in being exceptionally thin, light and tender, or weak in their fibrous structure.” it can be seen that in some instances gloves would be a perfect outlet, with others going to fancy goods, musical instruments and the like.
Arnold also says that “slunk is fairly general in the English speaking countries, but deacon is a New England ruralism, which has spread throughout the United States, but not generally outside. “To deacon”was to play a shabby trick – thence, as one of several strained metaphors, to kill a calf while still very young. “Bobby” is a partial equivalent Ian some British territories; but all these terms are so local that it is hard to be sure what they do mean.”
The grain of the wool sheepskin when it has been split in order to prepare suede leather for manufacture into chamois leather. Normally tanned with vegetable materials for use as in shoe lining, bookbinding or leather goods.
Vegetable tanned sheepskin produced from a skin whose wool has been removed by the sweating process. Mazamet in France is a famous source of slats.
The lower flesh side section of a hide (normally) or a skin after it has been split. Normally made into a suede split.
Mechanical softening of leather. Done by hand by pulling skins over a moon shaped knife, but mostly by machines of which tow types are common. The old “grab” staker with crocodile jaws which come together at a point where the operator offers the hide or skin and pulls the leather away from him while he restrains it carefully and the vibrating through feed machine invented in Czechoslovakia in the sixties. The former is more precise, but is also more labour intensive and skilled, while if not used carefully will lead to tearing and loss of area.
A wooden device previously used in oil tannages especially for chamois. Two wooden hammers pound the oil into the leather prior to hanging in a hot room for the oil to oxidise. An eccentric wheel drives the hammers. This process is now done in drums where temperature and humidity can be carefully controlled.
The finish produced by running the surface of leather on an emery wheel, with the result of ruffling up the fibres and giving it a “nappy” appearance. The grain of leather may be suede finished (called nubuck) but the process is more appropriate to flesh or split surfaces. The name was applied (originally in France) to a glove leather of Swedish origin and only later to the finish that characterised the material.
A process for loosening the hair or wool on a hide or skin by hanging the pieces near together in a close atmosphere, thus encouraging bacterial action. It has now become comparatively rare, being confined to out of the way places or primitive industries, and to a few special trades like that centring about Mazamet in France.
The treatment of hides and skins with chemicals that react with the material in such a way as to prevent putrefaction in normal circumstances. Different tannin methods give rise to leathers with somewhat different degrees of resistance and slightly variable properties. Most leather is tanned with a solution of basic chrome sulphate, called chrome tanning, followed by the oldest method vegetable tanning. Minority tannages include alum, oil, and aldehydes.
The old English term applied to the process of making leather with alum to distinguish it from tanning in a strict sense, the latter term having been originally confined to leather making with vegetable tanning agents. The English word has now become nearly obsolete, but in French the distinction between tannage and megissage is still strictly drawn. In the French region of Millau the tourist guide in 2015 explained “Millau gloves, made by the taweries and glovemakers that grew up here in the 12th century, are in great demand for their texture, sophistication and elegance.”
Because the leather produced from tawing is very clean and white the tanners were often called white tawers, or white tawyers hence the modern surnames of whitear and whittear. There have been many variations of this term over the last 600 years.
Tawing, or tanning with alum, creates a leather that performs well in many circumstances but the alum will wash out with rain or regular water so items lost or discarded will quickly biodegrade, as opposed to vegetable leather which can last indefinitely if kept free from air – underground or in water.
In 2021 in the UK alum tanned leather is still being manufactured with cattle hides for gymnastic sweat bands and for cricket balls. Cricket balls are treated with natural red dye, wax and a top coat of shellac so they are well protected from the wet. This finishing system for cricket is not colourfast, though, hence the red stain bowlers get on their trousers; but changing the finish would spoil the swing of the ball.
For gloves alum tawing with skins like sheep and goat, in particular younger skins which offer the run required for a perfect fitting glove as well as a fine grain where the hair follicles are small and close together.
Alexander Watt wrote in LEATHER MANUFACTURE, A PRACTICAL HANDBOOK, TANNING, CURRYING, AND CHROME, LEATHER DRESSING, New York 1906:
“In the process of tawing however, the skins are subjected to the action of alum and salt, which, although they convert the skins into a substance resembling leather in some of its attributes, cannot be said to form a true chemical compound with the gelatine, inasmuch as the three substances gelatine, alum, and salt can be again separated by treatment with water, as proved by the researches of Davy.
The arts of tanning and tawing are therefore perfectly distinct, and have no relation whatever to each other. Some manufacturers of light leathers, however, carry on the process of tanning calf and seal skins, as well as the tawing of goat, kid, sheep, and other small skins.”
Thus often a Tawer, or Tawyer, was also known as a white leather maker. Sometimes also a distinction was made between a wet glover, who tanned their own leather, and a regular or dry glover who bought in tanned skins ready to cut. Well Into the 20th century many glovers in the UK made their own leather and it seemed to decline as tanning moved away from alum towards tanning with chromium which required too much skill with the management of the chemicals.
Shakespeare’s father was a tanner and glove maker. If you go to Stratford and visit his house you can see where he worked and it has been recreated as it used to look. On the tanning side he was called a “white tawer” indicating that he used an alum tannage on his local skins, mostly deer. He also handled sheepskins, and did get into trouble for selling wool where sales were regulated by a different trade body.
A process of stretching leather at certain stages in the manufacture by tacking it on a frame or board. The method seems crude and slow, but is very effective for counteracting the shrinkage which follows certain operations, without applying excessive strains on particular portions of a piece.
A modernised method of tacking to dry leather, using toggles to hold the leather instead of nails. Originally the toggles were fixed into holes in a perforated metal plate which was put in an oven. More modern machines find and clip the leather mechanically.
A method of drying leather taking advantage of the fact that moisture evaporates more quickly under vacuum. The wet leather is laid out on a wet steel plate (often slicked, a form of hand setting out) and the vacuum head brought down. After retanning and fatliquoring the leather can be dried to either 30% and then hang dried or in some circumstances fully dried direct. Drying only takes two to five minutes. A newer use of vacuum drying involves using a rubber base instead of stainless steel. While the leather is under vacuum this rubber base expands outwards, stretching the leather out from its centre. I have seen a page of newspaper pulled into jigsaw-sized pieces by this machine. It is not so good for taking out large amounts of moisture but good for the drying after conditioning and staking of soft leathers. Avoid using it just for area gain.
Wet Blue. Chrome tanned leather
Chrome tanning creates a blue colour in the leather and there is a natural safe resting stage just after tanning when the leather is both wet and blue. A significant stage in which leather is traded semi-processed worldwide.
Hides and skins with the hair or wool removed and preserved after a light aldehyde or perhaps aluminium tannage. More stable than pickle. Increasingly used as an alternate tannage for chromium, especially in the car industry Does not yet have all the properties of chromium.
White Tawing (whittawing)
Tanning with alum, called Tawing (which see, above). Tanning with alum, flour and egg yoke which creates a white leather which was often used in gloves and more widely, but limited by the fact that the process could be reversed by washing. The process of making Glacé Kid was an alum process. The combined term of whittawer seems to have started mostly in the 16th century but a number of modern surnames come from it.
The origins of tawing are far from certain and obscured further as Roy Thomson explained by confusing with the use of alum as a mordant in dyeing. The process using aluminium potassium sulphate probably goes back 3000 years to Mesopotamian times.