Leather is the skin of the animal which has been treated and tanned. The full skin of the animal is called a hide, and skilled leather crafters know the different qualities and characteristics of each section of the hide, and how best to use each section in their projects.
The butt is the best part of the hide, especially towards the rear and near the spine. Here the fibres are tightly packed together producing a strong leather with a uniform grain. Next is the shoulder, a softer section of the back, still of very good quality and often used for tooling. Finally, the belly—of lower quality with looser fibres as a result of the skin expanding and contracting during the life of the animal, making the leather more stretchy and flexible.
Obviously, this isn’t a sudden change in characteristics but more of a transition. For that reason, the butt is softer and more flexible towards the belly and firmer near the spine or middle section of the butt.
Cowhides are large enough that the leather can be sold by individual segments or cuts. Other animal hides such as pig, goat, and sheep are much smaller and are typically only sold as a whole hide.
The leather is also graded by the meatpackers for whom the hide is a by-product. The hides are marked from grade 1 to grade 4 according to the number or size of flaws such as cuts or holes in the surface (essentially determining its usable area).
When the leather arrives in the tannery it is rawhide. It then goes through a process which includes removing the hair, de-fleshing, pre-tanning, tanning, and drying where it becomes crust leather. This is either chrome crust or vegetable crust depending on the tanning process. The leather is then split and dyed.
The hide itself is made up of several layers, and the degree to which these layers are sanded and buffed down at the tannery determines the final classification of the leather.
There are five general classifications which can be thought about in terms of descending levels of quality, although each serves its own purpose in the leather industry: full grain, top grain, genuine, split-grain, and bonded leather.
Full grain leather
Full grain leather has only had the hair removed leaving the full natural thickness of the top grain leather. This means that the hide itself needs to be free from “damage” which is not all that common given that these are the hides from animals which may have scratches, scrapes, and bite marks from fights or from living in their natural habitat.
Full grain leather is also the strongest and most durable leather because the fibres are not sanded down and thus retains many of its natural characteristics. These natural characteristics may include pores, varying textures, slight variations in colour, and even small scars. All of this makes each individual full grain hide unique
Crucially, full grain leather can be split down to less than 1mm and still retain a great amount of strength and tear resistance. This enables crafters to “roll” the leather over on itself, as well as to skive the leather down to a wafer at the edges without it disintegrating in order to reduce the overall thickness of a leather product.
For all these reasons, top grain leather is the most expensive type of leather.
Top grain leather
Top grain leather has had a very thin layer of the top grain sanded or buffed down. This gives a uniform surface across the leather to which a final finishing can be applied, e.g. faux crocodile finishes to cowhide.
Genuine leather
“Genuine” leather is split leather which has had the top grain removed down to the corium junction. The term is confusing on products as it is not clear if it is being used as a classification or to state that the leather is real or authentic—which would apply to full grain, top grain, genuine, and split-grain leather, equally.
Split-grain leather
Split leather is the bottom piece of the hide once it has gone through the splitter. Because it has no grain layer, the fibrous structure is weak and tears easily. By coating this layer in polyurethane the leather is given strength and can look superficially like top grain leather. Suede is a split leather, often used in shoes for its breathability.
Bonded leather
Bonded leather is made from pulped leather scraps and offcuts that have been glued to paper or some sort of backing panel, coated with polyurethane and embossed with a leather grain design. Bonded leather is often used in leather craft to add structure and firmness to products.
The treatment of leather also determines its final characteristics. This could include the use of soluble dyes (to produce aniline leather), soluble dyes with a small amount of pigment which leaves a protective layer (semi-aniline leather), embossing with a grain effect, injecting waxes and oils into the hide to create pull-up or oily pull-up leather, or even creating an uneven layer of pigment to create a distressed or vintage look.
