Tanning

"Tanning is the process of treating the hide of an animal with an agent, called tannin, that displaces water and combines with and coats the collagen fibres. Tanning increases resistance to heat hydrolysis (decomposition caused by water), and micro-organisms." Encyclopaedia Britannica

The preparation of animal skins for use as leather has been practised in some form in Britain since the Stone Age, when animal skins would have been used to protect humans from the weather and their feet from stones and thorns. Evidence exists for the use of leather by the Sumerians as far back as 6,000 BC, and preserved specimens dating to 5,000 BC have been discovered. The Egyptians are also known to have used leather in everyday life.

The fact that these skins would have rotted easily and often been very stiff was a problem but ways of softening and preserving them were discovered. At first skins were probably dried in sunlight, then later they were soaked in water and dried over a fire and later still it was discovered that certain vegetables, twigs, leaves and bark helped to preserve the skins.

The ancient Greeks and Romans appear to have had more complex methods of treating animal skins to produce leather of various quality.

In the Middle Ages wood ash and lime were used to treat and preserve the hides, and much later the cleaned hides were treated with dog, hen and pigeon dung. These procedures were later replaced with slaked lime (lime mixed with water).

With the increased demand for leather shoes, gloves, hats, horse harnesses, coats and many other items the tanning industry in Britain experienced a boom that began in the late 16th century and continued up until the 19th century. Towards the end of the 19th century technology and machinery had advanced to the stage where tanning could be undertaken on a large scale. Synthetic tannins were introduced in 1911 and as there was no longer a need to locate tanyards near to a supply of bark many of the smaller-scale tanyards ceased to operate.

The tanning process

There are several stages to the tanning process. Firstly the skins were thoroughly washed and soaked in water to remove any traces of blood that could discolour the leather. The washing would take place in specially-built pits, or more commonly, in a nearby stream so the waste was taken away.

The leather industry is traditionally associated with bad smells and pollution. Tanneries were generally located close to a stream or river to ensure a plentiful supply of water for processing and effluent removal. Tannery waste includes proteins, hair, lime, salt, acids, tannins, dyes and oils. Today the processing of this waste involves biological treatment to break down these ingredients. However, in the Middle Ages and up to the 19th century the waste would have been left to wash away in the stream and could have contaminated water supplies for miles downstream.

The washed skins were then immersed in a solution of lime and water, which would loosen any hair and fat on the skin. Depending on the type of leather required the soaking times varied. Softer leather would be soaked in a weaker lime solution for a longer period, leather for shoes would soak for 8-10 days in a stronger solution and harness leather would soak for 12-14 days in a medium solution. Soft leather for shoe uppers could sometimes be left for up to six weeks in a very weak lime solution.

The de-hairing and de-fleshing of the skin involved placing it on a sloping surface usually made out of wood or iron. To de-hair a knife with a blunt, concave blade was scraped along the skin. The hair that was removed was often re-used in mortar, upholstery and felt for clothing. The flesh was removed with a double-edged two-handled knife, and could be processed to make gelatin and glue.

There was then a second washing of the skin to get rid of any traces of the lime solutions and remove any remaining hair and fat. Then the skin would be treated with tannins to preserve it.

Before the tanning began the hides would be cut into several pieces to separate out the various densities and qualities of the skin. The liquor for tanning would then be prepared in pits known as leeching pits where ground oak bark would be left to stand in water for up to several weeks to produce various strengths. The hides were then passed through pits containing an increasingly stronger tannin solution.

Once the hides had been tanned they would be washed and rubbed to remove any bloom/colouration. They would then be treated with oil such as rapeseed oil, linseed oil or cod liver oil to prevent the skin from drying out too quickly. The skins would then be hung on racks in a drying room for 7-10 days. The rooms would be quite warm with a gentle stream of moving air, and would also be dark to prevent any fading by the sun. It was important to get the speed of drying right as if a skin dried too quickly it would become stiff and brittle, while if it dried too slowly it would sometimes go mouldy. After drying, the leather was rolled to remove any creases.

The leather was now ready to go to the currier. A currier was a person who cleansed, stretched and softened the leather ready for it to be used in a number of different ways by the cobbler, saddler, glovemaker, milliner and so on. A currier would often have a workshop attached to the tanyard so that he always had a plentiful supply of new material; sometimes he would be the tanyard owner or the local shoemaker.

Tanning was an important industry in Herefordshire, as it complemented the county's huge numbers of cattle and sheep. Due to the strong smells from the raw hides the tanyards were mainly situated as far away as possible from built-up areas and close to an abundant supply of water - which after being used in the tanning process was fed into the nearest ditch. The busiest times for tanning in Herefordshire were during the May and October Fairs when skins and bark were brought into the area to begin the twelve-month tanning process.

By the middle of the 19th century the products of tanning were being used by various other local trades such as fellmongers (who dealt in skin and hides), curriers (who treated leather to make it strong and waterproof), dyers, hat makers and woolstaplers.

The Herefordshire Historic Environment Record database has records of 35 sites classified as "tannery" or "tanning pit". All of the tanning sites on the database date from the post-medieval period (AD1540-1900), apart from two medieval sites in Bridge Street in Leominster, one medieval site in Bye Street in Ledbury, and one undated site in Sutton. They are spread across the county, but with a noticeable absence of sites in the south-west. However, the tithe maps (which mostly date to the 1840s) show many fields with names suggesting a connection with tanning. These field-names appear to be more spread out across the county and there are more sites in the south-west, which could indicate the location of tanyards that have yet to be discovered.

[Original author: Miranda Greene, 2005]