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|The numerous processes and types of skins and hides from which leather is made include:|
The hide or skin of an animal, bird or reptile after it has been tanned or treated by a chemical process which preserves it; hides are derived from the larger animals such as buffalo, elephant, horse, cattle, and skins from smaller animals, birds and reptiles. Man has used the skins of animals from Palaeolithic times for making garments and utensils but rawhide is a much more perishable material than leather; it putrifies, it dissolves and disintegrates into a sticky mass with damp heat and, when used for clothing, is stiff and unyielding. Only in a hot, dry climate is the putrifying process slowed so that in ancient Egypt, for example, rawhide was used for containers and hangings but, even here, few articles have been found intact. When Howard Carter opened the tomb of Tutank- hamun the rawhide base of his chariot was found to be glutinous.
It is not known exactly when, where or how man first learnt to transform raw animal skin into a non-perishable leather but articles of over 7,000 years old have been found in good condition. Early steps in the discovery of preserving animal skins were certainly the removal of the hair layer loosened by putrefaction and then a softening of the skins by oils, fat and brains, after which the inner, fat layer could be scraped away also, leaving the dermis, the central layer, which could then be tanned to make leather. Scraping tools of bone, flint and stone have been found at many ancient and primitive sites. Preserving and curing methods varied from the use of salt, alum, tannin from bark and smoking. Smoke curing was carried out by both Eskimos and North American Indians; the Eskimo women chewed the skin first to make it soft, wearing their teeth down to the gum, and the Indians used oils (see Eskimo dress and North American Indian dress).
The making of leather in modern times has become more a science than an art. Many different techniques and processes are used according to the type of leather to be produced and these are now fully mechanized, though industrialization came late to the leather industry and techniques did not change greatly over the years until the late nineteenth century.
Animal skins are composed of three chief layers, the outer epidermis which contains the hair, glands and blood vessels, the fibrous centre dermis or corium and the inner, fat layer. The outer and inner layers must be removed and the centre one treated in order to preserve it and make it into leather. The outer epidermis is removed by soaking the skin in liquid in which chemicals such as lime has been dissolved, then scraping it off. The fat layer is cut off with a sharp knife, a process known as fleshing, now carried out by machine. The remaining, central layer is then washed and cleansed. Chemicals are used now but the traditional process over the centuries was to treat it with dung, preferably from dogs, hens or pigeons, to set up bacterial fermen- tation and so cleanse and soften the material.
Three principal methods have been used through the ages to transform this cleansed central layer of the animal hide into leather: tanning, tawing and chamoising and these processes produce different kinds of leather. Tanning has been the most impor- tant method in which the skins are preserved, by the chemical properties of tannin found in vegetable matter. The earliest way of doing this was to dig a pit and lay the skins in this one on top of the other with layers of oak bark and galls between each layer and on top; the pit was then filled with water. After two or three months the pit was emptied and refilled with new bark and more water and this was repeated, the whole process taking over a year to complete. An alternative source of tannin was introduced into Western Europe in the later Middle Ages in the form of sumac from the east. In modern processes, the tanning time is reduced greatly by the use of concentrated extracts of tannin.
The tawing method of making leather is a very ancient one. It was used in ancient Egypt, Assyria and Babylon and India; in Europe, the Greeks and Romans used tawing and it was widely employed in the Middle Ages in Europe. This is a mineral process using alum and salt and originally produced a white leather, though later it was dyed in colours. After the Moorish conquest of Spain in the eighth century in Cordova a process of tawing leather was practised which was made from the mouflon sheep (see Furs). Cordovan or 5,panish leather became famous in Europe during the Middle Ages and most prized was the scarlet leather dyed with kermes. Even- tually the process was carried out in aU parts of Europe and the craftsmen known as cordwainers (from Cordova) though, due to specialization in footwear, the term was later retained for a shoe-maker or repairer (French cordonnier, English cordwainer).
Chamoising was a process using oil, especially cod-oil, which produces a soft leather. The term derives from the original use of chamois skins for the process and a soft leather later produced is known as wash-leather, which is derived from the underside of sheepskin, split so that the outer side can be used as a grain leather, Wash-leather is also called shammy, a corruption from chamois. The beautiful soft leathers of the North American Indian were produced by the chamoising process as also was buff leather, so-called because it was originally made in the Middle Ages from buffalo hide. The word buff applied to the colour derived from this leather.
After the tanning and cleansing was completed a number of finishing processes were carried out: working in fat or dubbin to give greater flexibility, rolling or hammering to consolidate the fibres, waxing to make waterproof, staining or dyeing to give different colours and Patterning the surface. Among the patterning processes were nap-raising and boarding. The numerous processes and types of skins and hides from which leather is made include:
| © Ragnar Torfason|
2006 March 28