Case-Hardening with ParkWest Arms

Parkwest Arms, formerly Dakota Arms, is pleased to offer color case hardening services to manufacturing and individual customers in search of a truly unique and legendary appearance for the rifle, shotgun, revolver or pistol of their dreams.
Shooters, firearms collectors and firearm historians are drawn to color case hardening as it both strengthens and protects individual gun parts and produces a lustrous, beautiful finish that is truly unique from piece to piece, but many new to the process ask - what is case hardening?
The answer blends the artistry of old-world metalworking; heat treating and surface hardening of low-carbon steel with wood and bone charcoal, with gunsmithing expertise. Case hardened steel components feature a rugged, carbon-rich surface that also happens to be both distinctive and attractive, hearkening back to a time when gun parts were case hardened out of necessity for strength and reliability.

[@ronaldjohnson1474]

Just a little more info would've made this vid relevant. Bone, charcoal, salts, etc.