Simply put, leather is made from animal skin through very complicated physical (mechanical) processing and chemical treatment. Different animal skins and changes in processing methods have created a variety of leathers. Traditionally, 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 useless things from animal skin, such as hair, fat, various glands in the skin and soluble protein, and to treat the collagen fibers of animal skin (that is, the main body of leather) to facilitate post-processing and improve the quality of leather.

The main processes at this stage are: soaking, removing meat, unhairing, liming, degreasing, softening and curing.

(2) Tanning stage, the main purpose is to change the collagen fiber structure of animal skin into leather by chemical methods. At the same time, it also determines the quality and properties of the obtained leather.

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

(3) In the finishing stage, its main purpose is to enrich some special sensory properties of leather, such as thickness, softness, color, surface state, water resistance and so on.

The main processes at this stage include peeling, smoothing, neutralization, dyeing, fatliquoring, drying, softening, flattening, leather grinding, painting and embossing.