When talking of the different types of leather, it is important to understand that the topic can be addressed on several levels, in fact the various types of leather available on the market can be divided according to different criteria:
- The type of tanning
- The layer of epidermis used ("Split" or "Top-Grain")
- The animal used
- The type of finishing of the surface
- The leather cut
- The usage
The first step to define the main characteristics and differences between skins is first of all to evaluate the type of treatment and tanning to which they are subjected in order to preserve and process them. This is because the choice of the type of tanning influences the finishing and cutting of the various parts which in turn have consequences on the possible uses of the material. For example, if a bull hide is left whole, it will certainly be chrome tanned and it will be used for furniture, while in the case in which this should be vegetable tanned, it will be cut into various parts and the main use will be that of belts and saddlery.
Leather types by tanning method
The set of all the processes that lead to the production of leather is commonly defined as "tanning industry", namely the industrial sector that produces leather, recovering and enhancing a by-product of the food industry: raw animal skin from slaughter houses.
The first step is the tanning. Tanning is the chemical operation that transforms putrescible skin into a rot-proof material, i.e. leather. The most common types of tanning are the chrome tanning and vegetable tanning: the main difference between the two lies in the use of different tanning agents, of chemical origin in the case of chrome tanning and of natural origin in the case of vegetable tanning. We can therefore conclude that based on the tanning method used we can identify two main types of leather:
- Chrome tanned leather
- Vegetable leather
Leather types by grain layer (split vs grain)
In some cases, before the tanning there is a process called "splitting" of the skin. The leather coats, originally too thick for use in any type of manufacture, must be split both for process reasons and for reasons of production and economy. A moving blade divides horizontally the full-thickness skin and separates it into two parts: "Split", the layer obtained from the side of the meat, and "Grain", the one obtained from the part of the animal's hair. Thanks to this process we obtain two products with very distinct characteristics and with expected uses that vary according to the subsequent processing steps. For example, the bovine split, subsequently tanned with chrome, would be a good product for shoes making.
Leather types by animal
As is known, there are many types of leather that are distinguished according to the animal used to make them, wanting to list the main ones, we can find:
- Bovine hides (cows, oxen, bulls, calves, etc.)
- Sheep and goat skin (rams, sheep, lambs, goats, cross-breeds etc.)
- Exotic leather and skins (ostriches or reptiles such as crocodiles, snakes, lizards, iguanas etc.)
- Fish skins (wolf fish, salmon, eel etc.)
- Fine fur coats (minks, foxes, opossums, etc.)
- Skins of wild animals (deer, wolves, fallow deer, gazelles, etc.)
The most commonly used are obviously the first two kinds, since they are those with the least minor environmental impact and do not threaten the terrestrial fauna, since the skin represent a recycled material with respect to the primary need to feed the populations.
Leather types by finishing of the surface
The leather obtained from the first stages of tanning can subsequently pass to the finishing process, a process by which the leather takes on the characteristics of color, strength and quality that allow it to be used in the most varied areas. The main finishing processes, without getting too specific, are the following:
- Crust or Semi-Finished Leather: it is the name that takes the leather or the skin in the case it is not fully finished, but left in the natural state after pre-tanning and tanning.
- Aniline and Semi-Aniline Leather: it is a type of finishing that keeps the surface of the skin (also called grain side) uncovered and visible to the naked eye. The treatment takes place thanks to the immersion of the skin in transparent dyeing tanks which gives the color product keeping the pores typical of the animal's skin visible. The semi-aniline leather with respect to the first one, instead foresees also a light use of covering pigments, aimed to protect and uniform the surface and partly to mask the defects.
- Pigmented Leather: it differs from the leather finished with pure aniline especially in the final appearance. Aniline, as we know, standardizes the surface and the color that comes out of the bath dye, but it does not eliminate absolutely any imperfection or defect present on the vast majority of skins sent for production; for this reason the corrected-grain leather are commonly used. Each skin has unique characteristics and defects that can vary with respect to different factors. We do not want to dwell here on the origin and nature of these defects: let's just say that very often aniline finishing accentuates the natural defects rather than limiting them. It is therefore necessary to resort to some sort of escamotage, in particular with the use of pigments, it is possible to mask defects more or less heavily; from this process also derives the distinction between aniline, semi-aniline and pigmented leather. The more massively the pigments are given, the more the skin moves away from the pure aniline finish and becomes precisely pigmented. With pigmented leather, part of the naturalness is lost but a great uniformity of the leather is obtained at a much more accessible price. The techniques of processing leather of this type, also called corrected grain leather, have now reached a level of such refinement that it often gives a very pleasant appearance and above all is much appreciated by the market.
- Printed Leather: it is a kind of leather, aniline, semi-aniline or pigmented, that has undergone a printing process carried out by means of special presses or rollers, which impress or draw particular textures on the skin with the aim to imitate the characteristics of some animals (for example, reptile print leathers) or to recreate fantasy designs.
- Dry-Milled Leather: of this type of finishing you do not hear about very often, in fact it is a purely technical term and refers to a particular finishing of the leather. It is a process that consists in inserting the skins in some drums that through movement and heat give the leather a worn and wrinkled look, giving it a particular and different appearance. This type of processing can be performed on a wide variety of leathers, from deer to calf or ovine hides, in any case it will be the buyer's choice. Depending on the object or item that you want to create, you will choose the type of leather, the type of color, the surface finishing and finally the possible milling effect. With this type of work you can make numerous objects, accessories and clothing, it's just a matter of taste and imagination and the products created will have the added value of a unique, natural and unrepeatable texture.
- Suede: it is a finishing of the skin that is obtained by tanning and finishing the less "noble" layer of the animal's skin, the "split". It has a soft and silky appearance and is usually chrome tanned.
- Nubuck: similar to suede but more expensive and valuable, it is a finishing of the grain side of the leather that is sanded to obtain a velvety, soft and refined surface.
Although these types of leather and leathers are the most common, for the sake of completeness it is necessary to specify that the types of leather and leather finishing do not end with this list, but there are many others, such as patent leather, brushed, buffered, laminated, nappa, greased, hair-on, etc., which are not the subject of this article.
Leather types by the cut
The types of skin and leather are identifiable and classifiable also on the basis of how the skin is cut, or based on the shape of the animal itself, this obviously influences its use, since, for example, a very small skin, probably it will not be the most suitable for making long belts. Among the main types we find:
- Half skins: such as calf sides, cow sides
- Bovine shoulders
- Bovine double butts
- Double front shoulders
Each cut has its particular characteristics and uses, and is usually tanned and finished in the most appropriate way to the shape and therefore to the use that it must be made of. The subdivision scheme of a whole bovine leather is given as an explanation.Basic scheme of subdivision of a cowhide
Leather types by application
Finally, based on the intended use of leather, various types of material can been identified:
- Leather for handbags, usually this category includes both chrome and vegetable tanned calf skins, cowhides, sheep and goat skins of not too high thickness.
- Leather for furniture and upholstery, in this category we often find generous sized skins, such as whole cowhides or bull hides.
- Leather for clothing and jackets, they are soft and light, also called "nappa leather", with thicknesses below one millimeter, usually lambs, rams and calves.
- Leather for shoes, these skins have thicknesses of between 1 and 2 millimeters (3-5 oz.) and can be of the most varied types and finishes.
- Leather for belts and saddlery, they are usually vegetable tanned leather hides with thicknesses over 2 millimeters (6 oz. and up), such as the double butts or the shoulders of a bull, but if lined, every kind of leather could be used for this purpose.