Technology plays a very significant role in leather manufacturing. The types of are various types of hides and skins which are converted into leather by using. Abstract. Hides and skins used as a raw material for leather manufacture may be IUE commissions, Updated October, B. perpemethico.cf INTRODUCTORY SKETCH OF LEATHER MANUFACTURE. The object of tanning. Washing and soaking. Removal of hair by liming. Unhairing by putrefaction.
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PDF | A panoramic overview of the leather world market is given. The industrial tanning process is schematically explained giving a general outline of how an. In the leather manufacturing sector, standards have been created by the 'Leather The use modern process chemicals and suitable leather manufacturing. As civilization advanced, preserving hides and tanning them into leather became a hide before it was delivered as leather to the saddle maker, harness maker.
Finishing operations can include oiling, brushing, buffing, coating, polishing, embossing, glazing , or tumbling , among others.
Leather can be oiled to improve its water resistance. This currying process after tanning supplements the natural oils remaining in the leather itself, which can be washed out through repeated exposure to water. Frequent oiling of leather, with mink oil , neatsfoot oil , or a similar material keeps it supple and improves its lifespan dramatically.
Some common types include: Vegetable-tanned leather is tanned using tannins extracted from vegetable matter , such as tree bark prepared in bark mills. It is the oldest known method.
It is supple and brown in color, with the exact shade depending on the mix of materials and the color of the skin. The color tan derives its name from the appearance of undyed vegetable-tanned leather. Vegetable-tanned leather is not stable in water; it tends to discolor, and if left to soak and then dry, it shrinks and becomes harder.
This is a feature of oak-bark-tanned leather that is exploited in traditional shoemaking. In hot water, it shrinks drastically and partly congeals, becoming rigid and eventually brittle.
Boiled leather is an example of this, where the leather has been hardened by being immersed in hot water, or in boiled wax or similar substances. Historically, it was occasionally used as armor after hardening, and it has also been used for book binding.
Chrome-tanned leather, invented in , is tanned using chromium sulfate and other chromium salts. It is also known as "wet blue" for the pale blue color of the undyed leather.
The chrome tanning method usually takes approximately one day to complete, making it best suited for large-scale industrial use. This is the most common method in modern use.
It is more supple and pliable than vegetable-tanned leather and does not discolor or lose shape as drastically in water as vegetable-tanned. However, there are environmental concerns with this tanning method, as chromium is a heavy metal. Aldehyde-tanned leather is tanned using glutaraldehyde or oxazolidine compounds. It is referred to as "wet white" due to its pale cream color.
It is the main type of "chrome-free" leather, often seen in shoes for infants and automobiles.
Formaldehyde has been used for tanning in the past; it is being phased out due to danger to workers and sensitivity of many people to formaldehyde. Chamois leather is a form of aldehyde tanning that produces a porous and highly water-absorbent leather.
Chamois leather is made using marine oils traditionally cod oil that oxidize to produce the aldehydes that tan the leather. Brain tanned leathers are made by a labor-intensive process that uses emulsified oils, often those of animal brains such as deer, cattle, and buffalo. They are known for their exceptional softness and washability.
Alum leather is transformed using aluminium salts mixed with a variety of binders and protein sources, such as flour and egg yolk. Alum leather is not actually tanned; rather the process is called "tawing", and the resulting material reverts to rawhide if soaked in water long enough to remove the alum salts.
Grades[ edit ] In general, leather is produced in the following grades: Top-grain leather includes the outer layer of the hide, known as the grain, which features finer, more densely packed fibers, resulting in strength and durability. Depending on thickness, it may also contain some of the more fibrous under layer, known as the corium. Types of top-grain leather include: Full-grain leather contains the entire grain layer, without any removal of the surface.
Rather than wearing out, it develops a patina during its useful lifetime. It is usually considered the highest quality leather. Furniture and footwear are often made from full-grain leather. Full-grain leather is typically finished with a soluble aniline dye. Russia leather is a form of full-grain leather. Corrected grain leather has the surface subjected to finishing treatments to create a more uniform appearance.
This usually involves buffing or sanding away flaws in the grain, then dyeing and embossing the surface. Nubuck is top-grain leather that has been sanded or buffed on the grain side to give a slight nap of short protein fibers, producing a velvet-like surface. The chemicals added during crusting have to be fixed in place. The culmination of the crusting sub-process is the drying and softening operations.
Crusting may include the following operations:. For some leathers a surface coating is applied. Tanners refer to this as finishing. Finishing operations may include:.
In addition to the other environmental impacts of leather , the production processes have a high environmental impact, most notably due to:. Pesticides are also often added for hide conservation during transport.
Tanning is especially polluting in countries where environmental norms are lax, such as in India - the world's 3rd largest producer and exporter of leather.
Very clearly, the process remains highly polluting all the same. In Kanpur , the self-proclaimed "Leather City of World" and a city of 3 million people on the banks of the river Ganges , pollution levels were so high that, despite an industry crisis, the pollution control board has decided to seal 49 high-polluting tanneries out of in July The higher cost associated to the treatment of effluents as compared to untreated effluent discharging leads to environmental dumping to reduce costs.
No general study seems to exist, but the current news is rife with documented examples of untreated effluent discharge. In November for instance, it was discovered that one of Uganda's main leather producing companies directly dumped its waste water in a wetland adjacent to Lake Victoria.
From Wikipedia, the free encyclopedia. Main article: Tanning leather.
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