As mentioned previously, leather is a mixture of fibres that are unevenly and more or less densely blended together. On the outermost layer, the fibres are packed together tightly, making the hide nonporous and waterproof. The fibres in the lower layer are loose, resulting in a very porous hide. This structure is more elastic and malleable. The characteristics of leather therefore depend on the density and porosity of the fibres.
With full-grain leather, once it is tanned but otherwise unprocessed, the entire thickness of the hide is used on the top part of the upper, with the outer membrane of the hide exposed. This type of leather is highly resistant and waterproof and has a smooth-out finish. Full-grain leather is, however, very expensive because the surface must be free of any imperfections. Eliminating folds, scuff marks or other abrasions reduces the usable surface of the hide, thereby raising the price.
The term “grain split” applies when only the outermost layer (top grain) of a hide is used on the top of a shoe or boot after the hide has been split into two or more layers. Although not a full-grain leather, split leather has most of the same properties: it is waterproof, resistant and has a smooth-out finish. It is, however, more supple because it is thinner and more elastic. The result is lighter footwear with less support. The leather is split in order to obtain a larger usable surface of hide (a grain layer and a flesh layer), which is more profitable.
The term “flesh split” refers to the inner or lower layer that has been separated from the hide. In other words, the whole leather—or full-grain leather—is split into two (or more) layers: the outer or top-grain layer and the lower or flesh-split layer. Very thick hides can produce two flesh layers in addition to a grain layer.
Suede is created by sanding the split leather surface to roughen it up. This leather is more porous and supple and less waterproof than the untreated split leather. It has a more uniform appearance and a smoother finish.
Nubuck is a leather finishing process, not a type of leather. Nubuck can be created using full-grain or grain-split leather. It is produced by sanding the top-grain leather surface. Leathers that have undergone this finishing process have the same properties as those that have not; they do, however, lose some waterproofness. The advantages of nubuck compared with smooth-out leathers are price and esthetics. Since sanding eliminates imperfections in the top grain, resulting in a larger usable surface of hide, the leather is less expensive. Many people also like the suede-like finish of nubuck.
This leather is the result of a finishing process. It begins as a flesh layer (suede, flesh-split leather or rough-out leather), to which a considerable amount of fats are added during tanning. The term “waxed” is not really accurate, since oil is used. The process results in a highly waterproof leather that prevents ventilation and the elimination of moisture through the pores.
The term “rough out” can be applied to several leathers. Any leather whose flesh layer is used for the top of the upper is a rough-out leather. This term, however, generally refers to a full-grain leather that is turned inside out. The flesh side provides an abrasion-resistant finish. It is, however, more porous and less waterproof.
Pigskin, as the name implies, is a leather made from the skin of a pig. It is thinner and more supple than cowhide and offers less support. It is more often used for lighter dayhiking shoes or boots or for gussets and linings.
Top-of-the-line shoe manufacturers often use full-grain leathers. The tanning process used to prepare the leather, however, affects its properties. The same hide can produce leathers with varying degrees of waterproofness, resistance and suppleness. For this reason, leathers on the market have different names, which are often trademarks:
