What is side leather?

One of the questions I’m most frequently asked about shoes is over the different leathers used for the leather uppers. In particular what exactly is side leather as opposed to calf leather?
The leather buyer is a hugely important role at the shoe factory and since there is no official standardized grading of leather it is down to the skill of the leather buyer to determine which hides and which part of the hides will be best suited to different roles in the footwear which the factory will be producing. In addition the hide can be quite thick and may be cut horizontally to provide different layers of the hide for different purposes.
Side leather is the term used for hide from a mature animal. It is also known as corrected grain leather as the hide can have blemishes such as scratches which will need to be removed before the hide is usable. Side leather may not be the very top layer of the hide and since it comes from an older animal can be relatively stiff. This stiffness can make the leather more susceptible to creasing and cracking with wear. Side leather invariably has a higher shine finish and will not show the grain of the hide.
Calf leather, as its name would suggest, comes from a younger animal. It is therefore much more pliable than older side leather. The suppleness of calf leather means that it will last longer than mature hides. It is more expensive than side leather and since the hide is thinner it is not possible to get as many layers from the hide as is possible with side leathers. Therefore it is usually the very top layer of the hide which is used and the natural grain of the hide will usually be visible.
In my view if you are looking for an instantly shiny shoe which will retain this shine easily then you may prefer a side leather. If however you are happy to put a little effort into polishing your shoes and would like a more supple leather which will last longer than look for calf leather.