What happens to a hide after slaughter
A fresh animal hide is mostly collagen, a structural protein arranged in long, bundled fibers. In a living body, those fibers are continually maintained. Once the hide is removed, that protection is gone: moisture, enzymes, and microbes can begin breaking its proteins apart, much as they do in other tissue.
Tanning changes the collagen so it is less prone to that breakdown. In chromium tanning, chromium salts bind to sites on collagen molecules, forming links that help hold the fiber network in a more stable arrangement. The hide becomes leather: still flexible, but less chemically vulnerable than untreated skin.
Stable does not mean indestructible
The added links make it harder for heat and microbial activity to unravel collagen, but they do not make leather immune to decay. Prolonged dampness can encourage mold and other damage, while heat, light, and harsh chemicals can degrade the material in different ways. Leather lasts because tanning slows the processes that would otherwise dismantle its structure—not because the hide has become incapable of changing.
That is why a leather object can remain usable for years under ordinary care, yet deteriorate quickly if it is stored wet: the treatment stabilizes its fibers, but the surrounding conditions still matter.
