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Do you know what leather is?
Leather is not simply the skin of a dead animal; it is a material made by a tanner. Once an animal has been killed for food, the skin becomes a waste product, which could be thrown away and allowed to decompose. Instead, it is transformed into a flexible, tactile material with a multitude of uses. Leather workers have long been aware of the special nature of leather, but it was not until the coming of microscopy that the underlying structure of leather was discovered and its secret revealed. From the leatherworker's point of view, the most important part of an animal skin is the corium.
Let’s see why Corium?
The corium consists mainly of the protein collagen, the fibers of which are grouped together into 'bundles'. It is the three-dimensional interweaving of these bundles of fibers throughout the thickness of the skin that gives leather its unique structure and adaptability. The largest bundles are found in the middle of the corium, and the fibers become finer and more closely woven towards the surface of the grain. It is the organization of the bundles of fibers and their ability to move in response to stresses and strains that give leather its characteristics its flexibility, strength, elasticity, malleability and ability to breathe. By studying the structure of the fibers, leather chemists have discovered how to affect the angle at which the fibers are woven and so to produce a range of leathers suited to a variety of specific needs.
Types of Leather:
In general, leather is sold in four forms:
a. Full-grain leather refers to hides that have not been sanded, buffed, or snuffed (as opposed to top-grain or corrected leather) to remove imperfections (or natural marks) on the surface of the hide. The grain remains allowing the fiber strength and durability. The grain also has breathability, resulting in less moisture from prolonged contact. Rather than wearing out, it will develop a patina over time. High quality leather furniture and footwear are often made from full-grain leather. Full-grain leathers are typically available in two finish types: aniline and semi-aniline.
b. Top-grain leather (the most common type used in high-end leather products) is the second-highest quality. It has had the "split" layer separated away, making it thinner and more pliable than full-grain.
Its surface has been sanded and a finish coat added to the surface which results in a colder, plastic feel with less breathability, and it will not develop a natural patina. It is typically less expensive and has greater resistance to stains that full grain leather, so long as the finish remains unbroken.
c. Corrected-grain leather is any leather that has had an artificial grain applied to its surface. The hides used to create corrected leather do not meet the standards for use in creating vegetable-tanned or aniline leather.
The imperfections are corrected or sanded off, and an artificial grain impressed into the surface and dressed with stain or dyes. Most corrected-grain leather is used to make pigmented leather as the solid pigment helps hide the corrections or imperfections. Corrected grain leathers can mainly be bought as two finish types: semi-aniline and pigmented.
d. Split leather is leather created from the fibrous part of the hide left once the top-grain of the rawhide has been separated from the hide. During the splitting operation, the top-grain and drop split are separated. The drop split can be further split (thickness allowing) into a middle split and a flesh split. In very thick hides, the middle split can be separated into multiple layers until the thickness prevents further splitting. Split leather then has an artificial layer applied to the surface of the split and is embossed with a leather grain (by cast leather).
Splits are also used to create suede. The strongest suedes are usually made from grain splits (that have the grain completely removed) or from the flesh split that has been shaved to the correct thickness. Suede is "fuzzy" on both sides. Manufacturers use a variety of techniques to make suede from full-grain. Reversed suede is grained leather, that has been designed into the leather article with the grain facing away from the visible surface. It is not considered to be a true form of suede.
Less-common leathers include:
Buckskin or brained leather is a tanning process that uses animal brains or other fatty materials to alter the leather. The resulting supple, suede-like hide is usually smoked heavily to prevent it from rotting.
Patent leather is leather that has been given a high-gloss finish. The original process was developed in Newark, New Jersey, by inventor Seth Boyden in 1818. Patent leather
usually has a plastic coating
Fish Leather popular for its motifs and its pigmentation. Mainly used for making shoes and bags, the fish skin is tanned like other animal skins. The species used include salmon, perch, sturgeons.
The following are not "true" leathers, but are synthetic materials that contain some leather fiber. Depending on jurisdiction, they may still be labeled as "Genuine Leather", even though the consumer generally can only see the plastic outer layer of the material and can't actually see any of the leather content.
Reconstituted leather is composed of up to 90% leather fibers (often scrap from leather tanneries or leather workshops) bonded together with a plastic or latex binder to create a look and feel similar to that of leather at a fraction of the cost. The resulting material is not as durable as real leather and is recommended for use only if the product will be used infrequently.
Bonded leather used for upholstery is a plastic (generally vinyl or polyurethane) material that contains about 17% leather fiber in its backing material. The plastic is stamped to give it a leather-like texture. Bonded leather upholstery is as durable as other plastic materials and its manufacturing process is more environmentally-friendly than leather production.
Bicast leather is a split leather with a layer of polyurethane applied to the surface and then embossed. Bicast was originally made for the shoe industry and recently was adopted by the furniture industry. The original formula created by Bayer was strong but expensive. The result is a plastic material that is slightly stiffer but cheaper than top-grain leather but has a much more consistent texture. Because its surface is completely covered in plastic, is easier to clean and maintain.