If the skins are not tanned, they can spoil quickly. In order to avoid this, they are soaked in brine (in a solution of sodium chloride, hydrochloric acid and water).
Raw skin can be made and worn supple but after rain and drying it will be stiff and rigid. And if he stays wet for long he rots.

First, the inside is cleaned on a hard surface with a scraper, a shard of bone or stone moved to the edges till the hide is completely scraped clean (the fleshing) and the skin looks white.
For fur you let the hair on the pelt. (Otherwise they are scraped.)

You can soak the skin a night in urine. Morning urine contains the most ammonia. By the action of ammonia and acids the skin pulls together. This makes the hairline closer and firmer. Then rinse the skin.

Raw skin is now rolled, if desired, smoked and used. Tanning makes it more durable.

In order to make leather the hair is removed. The skin is placed in (calcareous) water or water with wood ash. This allows for a bacterial and respectively a chemical attack of the upper skin layer. This contains the hair roots firmly. Due to the deterioration of the epidermis by rotting or lied they can be easily scraped off (the scudding).

Fur: a skin that varies from animal. (Aurelien Scholl)
Decadence: buy a coat of seal babies, because otherwise you will find it so sad for the trapper. (Hans Ferree)