I am currently running a roleplaying game where my player wants to work as a tanner but being honest i have no clue about how tanning and curing worked back when modern chemicals or equipment didn't exist. Can someone explain to me how it worked or point me to a source that explains how it is done?
Basically hides were soaked in urine. No wonder tanners were unpoular.
The Wikipedia page on tanning answers this question.
Formerly, tanning was considered a noxious or "odoriferous trade" and relegated to the outskirts of town, amongst the poor. Indeed, tanning by ancient methods is so foul smelling, tanneries are still isolated from those towns today where the old methods are used. Skins typically arrived at the tannery dried stiff and dirty with soil and gore. First, the ancient tanners would soak the skins in water to clean and soften them. Then they would pound and scour the skin to remove any remaining flesh and fat. Next, the tanner needed to remove the hair from the skin. This was done by either soaking the skin in urine, painting it with an alkaline lime mixture, or simply allowing the skin to putrefy for several months then dipping it in a salt solution. After the hairs were loosened, the tanners scraped them off with a knife. Once the hair was removed, the tanners would "bate" (soften) the material by pounding dung into the skin, or soaking the skin in a solution of animal brains. Bating was a fermentative process which relied on enzymes produced by bacteria found in the dung. Among the kinds of dung commonly used were those of dogs or pigeons. Sometimes, the dung was mixed with water in a large vat, and the prepared skins were kneaded in the dung water until they became supple from bacterial enzyme action, but not too soft. The ancient tanner might use his bare feet to knead the skins in the dung water, and the kneading could last two or three hours. This combination of urine, animal feces, and decaying flesh made ancient tanneries malodorous.