There are many resources on the internet that can explain the technical aspects of how leather is made, from sourcing, chemical structures and contents, materials used in processing, machinery, etc. etc. This isn't intended to cover any of these areas in detail, if you want to understand the specifics it would be best to research them individually, but to give a much briefer insight into how we get from animal to finished product, and to try and explain some of the terminology commonly used.
All skins have to come from an animal of some description. Avoiding any ethical issues, at GH Leathers we only use skins that are a by product of the meat industry, meaning the farming priority is food and the skin is of secondary value. This applies even to our exotic range - remember that we source globally and just because we don't eat certain foods here in the UK doesn't mean they aren't eaten elsewhere!
Once the meat is removed from the animal in the abattoir the pelts are collected and immediately covered and stored in salt to prevent them from decaying. The can remain in this state for some time but it is more common that they are sorted and sold and processed quite quickly.
The 'messy' end of the production process is often referred to as the preparatory stages and concentrates on further preserving the and preparing the pelts for tanning, and will involve some or all of the following - soaking the skins to clean them, fleshing, liming, unhairing (unless of course double face usage) degreasing and pickling. At this final stage the skins will be preserved fully and is an opportune time to begin sorting for grade quality and final product destination.
The next process involves tanning which in effect is the change from skin or pelt into what can be called leather. The principal difference being that a tanned skin can be dried out and form a flexible material and when wetted back will not putrefy. The types of tannage commonly used are chromium and vegetable. Chrome tan will leave the skins a pale blue colour - hence the term wet blue - and today will usually involve artificial chrome as this is more user friendly and is easier to deal with the waste. Chrome tanned leather will generally have more useful applications in finishing over the other common option of vegetable tanning. With this version only vegetable extract is used, no minerals, so whilst the leather is certainly environmentally friendly it does have limitations to its properties. Veg tanned leather is usually a brownish shade and will absorb water much easier than chrome tanned. It will also have poor resistance to light and colour swill tend to fade quicker.
The tanning process is where a lot of the technical knowledge concerned with leather making is required, and I have no intention of getting into the details here, other than to note that technology is ever evolving and processes constantly change to improve the properties of the finished product.
After tanning the leather is most likely sorted again to decide on its final usage - this could be for full grain leather but if the skin is not good enough it would be diverted into split or some other surface modification to disguise its faults. It is worth noting if the grain of a skin is too poor it may be selected for suede - this is the other side of the skin to the grain and would have been the part of the skin on the inside of the animal.
The creative aspect of leather production now comes into play as the leather is dyed, fatliquored, dried, conditioned, staked, shaved, and finished into the final desired article. These are all generally mechanical operations and will vary depending on the final product - garment leather would need to be softer and more flexible than soling leather,
The final stages may be a spry of some kind, for colour or effect, onto the grain, or and embossing or transfer print. If the grain isn't 'clean' (will not give good cutting) it may be buffed off to produce a nubuck. On heavy bovine skins they are split into sections, and each skins will produce a grain, split and suede layer to use.
Due to the vast array of skin origins and finished products, it isn't possible to detail exactly how each one would be made. Generally all leathers would go through most if not all of the above processes at some stage, to a greater or lesser degree. For example, a cow hide may need to be split and shaved to several times to reach a desired substance, where as a lamb skin is already inherently thin so would need only possibly to be shaved once, just to unify the substance across the skin.
So this is a very general outline of the basics of taking a raw skin from an animal and the type of processes it has to go through to reach a finished product. Please don't hang me should you feel the information isn't truly accurate - it's based on my own knowledge and experience rather than taken from the latest text books or technology papers. If there is anything of vital importance missing let me know - we are always learning!