Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide.
Several tanning processes transform hides and skins into leather:
Vegetable-tanned leather is tanned using tannin and other ingredients found in vegetable matter, tree bark, and other such sources. It is supple and brown in color, with the exact shade depending on the mix of chemicals and the color of the skin and is mainly used for tanning sole leather. Vegetable-tanned leather is not stable in water; it tends to discolor, and if left to soak and then dry it will shrink and become less supple and harder. In hot water, it will shrink drastically and partly gelatinize, 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 1858, is tanned using chromium sulfate and other salts of chromium. It is more supple and pliable than vegetable-tanned leather and therefore is mainly used in the tanning of upper leathers in the shoe industry. It does not discolour or lose shape as drastically in water as vegetable-tanned. It is also known as wet-blue for its color derived from the chromium. More esoteric colors are possible using chrome tanning.
Rawhide is made by scraping the skin thin, soaking it in lime, and then stretching it while it dries. Rawhide is stiffer and more brittle than other forms of leather, and is cut up into cords for use in lacing or stitching.
Leather—usually vegetable-tanned leather—can be oiled to improve its water resistance. This 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.
Types of leather:
In general, leather is sold in four forms:
Full-grain leather refers to the leather which has not had the upper "top grain" and "split" layers separated. The upper section of a hide that previously contained the epidermis and hair, but were removed from the hide/skin. Full-grain 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. Leather furniture and footwear are made from full-grain leather. Full-grain leathers are typically available in two finish types: aniline and semi-aniline.
Top-grain leather is the second-highest quality and 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, less breathability, and will not develop a natural patina. It is typically less expensive, and has greater resistance to stains so long as the finish remains unbroken than full-grain leather.
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.
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 (Bycast 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. A reversed suede is a 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.
Full grain leathers are therefore used in the better quality formal shoe. All Bradshaw and Lloyd's own brand of shoes, Trickers shoes, Flexwelts from Sanders shoes and the 1880 Collection from Loake shoes are all made with full grain calf leather. Visit our website www.bradshawandlloyd.com to view over 300 styles of shoe. Full grain leathers are also used in most Sebago shoes.