Tanning is the process where you treat hide (skin) with chemicals to make it to leather. Although the use of skins as clothing was used over millennia, tanning is known since approx. 7000 BC.
The first real tanning was with oak bark, which contains tannins – an impregnating substance – and later came the use of Alluminium (as in alum, a kalium/aluminiumsulphate) and Chrome (as in various chrome(III)salts).
Here it can be said that leather, tanned with chrome is more resistent and smoother than leather, tanned with other tanning agents.
Tanning is known to be extremely polluting and today there are also various mixtures of chemicals – with significantly lower environmental toxicity – which can be used.
The process is simple: the skin is cleaned of fat and tissue-remains and perhaps receives a treatment that removes the hair. Then the skin is pickled, cleaned again and soaked in a tanning bath. After a few days the skin is taken up, dried and made smooth.
Tanned hides with head and paws are a coveted hunting-trophy.