All About Leather

For those of you that have a fascination with leather goods, I am here to shed some insight of this wonderful material.
Leather is a material created through the tanning of hides, pelts and skins of animals, primarily cows. Leather is a very important clothing material, and its other uses are legion. Together with wood, leather formed the basis of much ancient technology. Leather with the fur still attached is simply called fur.
There are a number of processes whereby the skin of a dead animal can be formed into a supple, strong material commonly called leather. Vegetable-tanned leather is tanned using tannin (hence the name "tanning") 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 flesh. 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 plasticize, becoming rigid and eventually becoming brittle. Alum-tanned leather is tanned using aluminum salts mixed with a variety of binders and protein sources, such as flour, egg yolk, etc. Purists argue that alum-tanned leather is technically "tawed" and not tanned, as the resulting material will rot in water. Very light shades of leather are possible using this process, but the resulting material is not as supple as vegetable-tanned leather. Rawhide is made by scraping the skin thin, soaking it in lime, and then stretching it while it dries. Like alum-tanning, rawhide is not technically "leather", but is usually lumped in with the other forms. Rawhide is stiffer and more brittle than other forms of leather, and is primarily found in uses such as drum heads where it does not need to flex significantly; it is also cut up into cords for use in lacing or stitching, or for making dog toys. Boiled leather is a hide product (vegetable-tanned leather) that has been hardened by being immersed in hot water, or in boiled wax or similar substances. Historically, it was used as armour due to its hardness and light weight, but 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 does not discolor or lose shape as drastically in water as vegetable-tanned. More esoteric colors are possible using chrome tanning. Brain-tanned leathers are exceptionaly absorbent of water. They are made by a labor-intensive process which uses emulsified oils (often those of animal brains) and which has not been industralized. They are known for their exceptional softness and their ability to be washed.
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.
In general, leather is sold in three forms... Full-Grain leather, made from the finest raw material, are clean natural hides which have not been sanded to remove imperfections. Only the hair has been removed. The grain remains in its natural state which will allow the best fiber strength, resulting in greater durability. The natural grain also has natural breathability, resulting in greater comfort. The natural Full-Grain surface will wear better than other leather. Rather than wearing out, it will develop a natural "Patina" and grow more beautiful over time. The finest furniture, and footwear, are made from Full Grain leather.
Corrected-Grain Leather (also called "top-grain leather"). Corrected Leather is fuzzy on one side and smooth on the other. The smooth side is the side where the hair and natural grain used to be. The hides, which are made from inferior quality raw materials, have all of the natural grain sanded off, and an artificial grain applied. Top grain leather generally must be heavily painted to cover up the sanding and stamping process.
Suede is an interior split of the hide. It is "fuzzy" on both sides. Suede is less durable than top-grain. Suede is cheaper because many pieces of suede can be split from a single thickness of hide, whereas only one piece of top-grain can be made. However, as the look of full-grain is in demand, manufacturers use a variety of techniques to make suede appear to be full-grain. For example, in one process, glue is mixed with one side of the suede, which is then pressed through rollers; these flatten and even out one side of the material, giving it the smooth appearance of full-grain. Latigo is one of the trade names for this product.
Leather from other animals
Today, most leather is made of cow hides, but many exceptions exist. Lamb and deer skin are used for soft leather in more expensive apparels. Kangaroo leather is used to make items which need to be strong but flexible, such as motorcycle gloves. Kangaroo leather is favored by motorcyclists specifically because of its lighter weight and higher abrasion resistance as compared to cowhide. Leather made from more exotic skins has at different times in history been considered very beautiful. For this reason certain snakes and crocodiles have been hunted to near extinction.
In the 1970s, farming of ostriches for their feathers became popular. As a side product, ostrich leather became available and is currently used by all the big fashion houses like Hermès, Prada, Gucci, and Louis Vuitton. Ostrich leather has a characteristic "goose bump" look because of the large follicles from which the feathers grew.
In Thailand, sting ray leather is used in wallets and belts in the same way as regular cow leather. Sting ray leather is as tough and durable as hard plastic. The leather is often dyed black and covered with tiny round bumps in the natural pattern of the back ridge of an animal. These bumps are then usually dyed white to highlight the decoration.
Preservation and Conditioning of Leather
The natural fibers of leather will break down with the passage of time. Acidic leathers are particularly vulnerable to red rot, which causes powdering of the surface and a change in consistency. Damage from red rot is aggravated by high temperatures and relative humidities, and is irreversible.
Exposure to long periods of low relative humidities (below 40%) can cause leather to become desiccated, irreversably changing the fibrous structure of the leather.
Various treatments are available such as conditioners, but these are not recommended by conservators since they impregnate the structure of the leather artifact with active chemicals, are sticky, and attract stains.
Alex Matthews is a leather industry veteran involved in leather goods manufacturing for the last 15 years. To get additional information about the properties of leather please contact Alex at info@emiliooneto.com or /
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