Leather is an animal skin that has been denatured and decomposed by physical and chemical processing such as depilation and tanning. The leather is composed of natural protein fibers that are tightly woven in three dimensions. The surface has a special grain layer with natural grain and luster for comfortable hand.
In the process of human evolution, it has been found that some plant juices or mineral oils have a certain degree of enthalpy to the leather, and the raw material skin is soaked by the juice, which is more breathable and antiseptic. Therefore, the sheet material has physical properties such as softness, tear resistance, and tortuosity. The skin of this period really possessed the characteristics of leather products. And this juice is called a tincture. The tanning industry developed into a stable tanning agent in the middle of the last century is roughly divided into the following three categories:
1. Vegetable tincture: mainly silicone rubber, used in industrial leather or bottom leather.
2. Mineral tincture: mainly chromium salt, aluminum salt, used in various civilian leather. Such as clothing.
3. Organic tincture: mainly formaldehyde, glutaraldehyde, etc., used in fur suede and all kinds of fine skin.