Tanning: Difference between revisions
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The first stage is the preparation for tanning. The second stage is the actual tanning and other chemical treatment. The third stage applies finishing to the surface. | The first stage is the preparation for tanning. The second stage is the actual tanning and other chemical treatment. The third stage applies finishing to the surface. | ||
Preparing hides begins by curing them with salt. In wet-salting, the hides are heavily salted, then pressed into packs for about 30 days. In brine-curing the hides are agitated in a salt water bath for about 16 hours. The hides are then soaked in clean water to remove the salt and a lime/water solution to loosen the hair. The majority of hair is then removed using a machine with remaining hair being removed by hand using a dull knife, a process known as scudding. Depending on the end use of the leather, hides may be treated with enzymes to soften them. | Preparing hides begins by curing them with salt. In wet-salting, the hides are heavily salted, then pressed into packs for about 30 days. In [[brine]]-curing the hides are agitated in a salt water bath for about 16 hours. The hides are then soaked in clean water to remove the salt and a lime/water solution to loosen the hair. The majority of hair is then removed using a machine with remaining hair being removed by hand using a dull knife, a process known as scudding. Depending on the end use of the leather, hides may be treated with enzymes to soften them. | ||
Tanning can be performed with either vegetable or mineral methods. Before tanning, the skins are unhaired, degreased, desalted and soaked in water over a period of 6 hours to 2 days. To prevent damage of the skin by bacterial growth during the soaking period, biocides, such as pentachlorophenol, are used. | Tanning can be performed with either vegetable or mineral methods. Before tanning, the skins are unhaired, degreased, desalted and soaked in water over a period of 6 hours to 2 days. To prevent damage of the skin by bacterial growth during the soaking period, biocides, such as pentachlorophenol, are used. | ||
Revision as of 07:18, 14 December 2021
Tanning is the process of converting putrescible skin into non-putrescible leather, usually with tannin, an acidic chemical compound that prevents decomposition and often imparts color.
Modern methods of tanning
The first stage is the preparation for tanning. The second stage is the actual tanning and other chemical treatment. The third stage applies finishing to the surface.
Preparing hides begins by curing them with salt. In wet-salting, the hides are heavily salted, then pressed into packs for about 30 days. In brine-curing the hides are agitated in a salt water bath for about 16 hours. The hides are then soaked in clean water to remove the salt and a lime/water solution to loosen the hair. The majority of hair is then removed using a machine with remaining hair being removed by hand using a dull knife, a process known as scudding. Depending on the end use of the leather, hides may be treated with enzymes to soften them.
Tanning can be performed with either vegetable or mineral methods. Before tanning, the skins are unhaired, degreased, desalted and soaked in water over a period of 6 hours to 2 days. To prevent damage of the skin by bacterial growth during the soaking period, biocides, such as pentachlorophenol, are used.
Vegetable tanning uses tannin, from which tanning gets it name. Tannin occurs naturally in bark. The primary barks used in modern times are chestnut, oak, tanoak, hemlock, quebracho, mangrove, wattle, and myrobalan. Hides are stretched on frames and immersed for several weeks in vats of increasing concentrations of tannin. Vegetable tanned hide is flexible and is used for luggage and furniture.
Mineral tanning usually uses chromium. In the raw state chrome tanned skins are blue and therefore referred to as "wet blue". Chrome tanning is faster than vegetable tanning (less than a day for this part of the process) and produces a stretchable leather which is excellent for use in handbags and garments.
Depending on the finish desired, the hide may be waxed, rolled, lubricated, injected with oil, split, shaved and, of course, dyed. Suedes, Nubucks, etc. are finished by raising the nap of the leather by rolling with a rough surface.
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