The first stage is the preparation for tanning. The second stage is the actual tanning and other chemical treatment. The third stage applies retanning agents and dyes to the material to provide the physical strength and properties desired depending on the end product. This is known as Retanning. The fourth stage is used to apply finishing material to the surface or finish the surface without the application of any chemicals if so desired. This final stage is known as finishing.

Preparing hides begins by curing them with salt. Curing is employed to check putrefaction of the protein substance (Collagen) because of the chance of bacterial infection due to the time lag that might occur from procuring it to processing it. It removes the excess water from the hides and skins where water flows from inside because of difference in osmotic pressure. Thus the moisture content of hides and skins get greatly reduced. In wet-salting, the hides are heavily salted, then pressed into packs for about 30 days. In brine-curing the hides are agitated in a salt water bath for about 16 hours. Generally speaking, methods employed for curing greatly make the chance of bacterial growth unfavorable. Thus curing is also done by preserving the hides and skins at a very low temperature

The hides are then soaked in clean water to remove the salt and mainly to bring back the moisture content to a desirable level so that the hide or skin can be treated with chemicals in an aqueous medium. This process is known as "Soaking" and sometimes a hydrating agent is also employed along with water in a very low percentage for hides and skins which have become very dry.

Company resources：PTFE open meshes, Seamless belts, PTFE sheet
Read more：http://www.ptfeglassfiber.com/news/