The tanning of hides is a very ancient trade, certainly pre-Roman. Leather was made by drying and salting hides. After the Norman Conquest oak bark was used on cattle skins, alum and oil on the skins of horses, deer and sheep. The Severn had many tanneries on its banks, Bewdley for instance had everything needed for tanning, droves of cattle from the Welsh borderline, oak bark from the Wyre Forest, and good transport to the markets at Bristol.
Tanning took much water and older tanneries were always situated near streams or rivers and wells, with access to oak bark nearby. A tannery needed a large number of vats, 15 to 20 or more, but by the 17th century the vats were replaced by stone-lined pits in a tan-yard.
Hides from cattle were first soaked in a pit of milk of lime, then washed till all the lime was removed. This softened the skin, and the hair and fat scraped off with a two-handled, large blunt spoke shave, the skin being bent over a 'beam', a convex, sloping board. Nothing was wasted, the scrapings went to plasterers and tallow makers. The hides were then placed in a very weak sulphuric acid to open the pores, and the progressed through pits of bark liquor, the first of spent and weak strength, and so on getting stronger, till the last with fresh, powdered bark. The skins moved about, and the whole passage took about a year. The skins are then hung in sheds, usually by two storeys, and dried by circulating air from long walls of large louvers.
Curriers treated the rough tanned hides by soaking and shaving to required thickness. The leather was then impregnated with oil or tallow , then squeezed, rolled. etc. For different toughness and flexibility. In olden times, auxiliary leather trades, (shoes, saddles, candles, buttons, manures and horn) were all found nearby.