Why would a natural leather need to be tanned?

It will rot if you don't tan it. Same as people

How is leather made? How is leather made from hides?

Simply put, leather is made from animal skins through a very complex process of physical (mechanical) processing and chemical treatment. Different animal skins, as well as changes in processing methods, make a variety of leather. According to the traditional saying, the tanning process is generally divided into three stages: preparation stage, tanning stage and finishing stage.

(1) In the preparation stage, its main purpose is to remove all the useless things on the animal skin, such as hair, fat, all kinds of glands and soluble proteins inside the skin, etc., and the collagen fibers of the animal skin (i.e., constituting the main body of the leather), in order to facilitate the later processing and to improve the quality of the leather.

The main processes in this stage are: soaking, removing meat, dehairing, soaking ash, degreasing, softening, soaking acid.

(2) In the tanning stage, its main purpose is to make the collagen fibers of the animal skin change in structure by chemical methods, so that it changes from skin to leather. At the same time, it also determines the quality and properties of the resulting leather.

The main processes in this stage are: pretanning, main tanning and retanning.

(3) In the finishing stage, its main purpose is to enrich the leather with some special sensory properties, such as thickness, softness, color, surface condition and waterproofness.

In this stage, the main processes are: cutting layer, cutting, neutralization, dyeing, adding fat, drying, making soft, spreading, grinding leather, coating, embossing and so on.