The fundamental reason for the softness of leather is that during leather making, a leather simulation oil with a good degree of bonding with the leather fibers is introduced into the interior of the animal skin to form an oil film that fully covers the surface of the fibers in the leather, that is, between the surface of the fibers in the leather. It is separated by a layer of leather of suitable thickness to simulate an oil film, so that the friction between the fibers inside the leather is equivalent to the friction of oil molecules, so the leather will be very soft. The principle is similar to that of a sponge, except that the inner surface fibers of the dermis are separated by an oil film, so that there are slidable pores between the inner dermis, but its pores are smaller than those of a sponge, and the distribution of fibers on the inner surface of the dermis is not as good as that of a sponge. There are rules. 

However, in the natural state, the oil introduced into the leather will gradually volatilize and lose over time, or the oil film will be damaged due to other reasons. If it is hydrolyzed in water or in a high temperature environment, the leather simulates the oil film of oil. If it is destroyed, the oil will be volatilized and lost, so the fibers inside the leather will stick to each other, making the leather hard and brittle. Therefore, when the inner oil film of the leather is destroyed or the oil is lost, the surface between the inner fibers of the leather should be re-injected with high-quality oil that forms an oil film.

If you are intested in PU Leather, please contact WiniwPULeather at www.winiwpuleather.com.