Tanning (oak bark)

The history of this craft goes back to around the bronze age, some of the earliest bark tanneries would have been pits lined with timber and filled with bark, bark rubbed directly into the hide or case skinned hides filled with bark and water and hung from a tree to tan.

There are two types of leather – full grain and top grain. Full grain leather is leather that has not been tampered with after removing it from the animal – the hair is removed and the grain or epidermis is left on. Top grain leather is worked with to cover up any scars or blemishes on the skin and is usually sanded and sprayed.

The process of tanning varies according to the intended use of the leather; the end product. However, generally in the preparation for tanning, larger animal hides are divided and cut according to body areas, while smaller animals (e.g. calf, goat, pig and reptiles) are left as one piece. Firstly the hair must be removed from the skin. The hides and skins are in water to be washed and rehydrated, with lime liquors used to loosen the hair and plump the hide. The hair that has been removed is sold on to plasterers or felt manufactures. The hides and skins are naturally uneven and of different thicknesses. Therefore, in order to even them out they are run through a plotting machine. Thickness throughout a hide differs, hence why leathers are shown to have different thicknesses on their labelling.

The tanning process consists of putting hides in weak solutions of tannic acids which gradually increase in strength. The tanning operation varies in time from 3 weeks to 3 months, dependent on the type of hide being tanned and the thickness of it. The leather is then dried in such a way that the leather does not diffuse into ‘grain’ or the ‘flesh’ using oils applied to wet leather which form a film to arrest this diffusion. While still wet, the leather is ‘set out’ removing creases and ‘rolled on’ to help make the characteristic smooth surface of leather. The leather is thoroughly dried out and ‘rolled off’ on very heavy pressure rollers which gives the polish to the finished leather.

England traditionally used oak bark to tan skins and hides. The traditional oak bark process differs slightly from that mentioned above. Oak bark is stripped from trees during the spring and summer seasons. It is dried out for two or three years and then ground down. The tan is soaked out of the bark using cold water. When the tan is strong enough, it is pumped up to the tan yard. There are different pits which the hides pass through. They are suspended by sticks for the first three months. The sticks are then removed and the hides are laid flat, one on top of the other into deeper pits where they remain for nine months. The raw hide becomes leather. When the hides are taken out of the pits, they are dried for two or three days, at which point they are ready for finishing. A downside of using oak bark today is that it is a slow process, requiring twelve months for tanning. However, it is hardwearing and produces a strong textile. Oak bark tanned leather lies at the high end of the market.

In Scotland tanners used combinations of different types of barks and plants, some of the earliest tanning sources on the Islands were Tormentil. In the Highlands and the area around Fife Peat tanning was practiced by submerging hides in Peat bogs or combining with bark.

Different people do different parts of the job. There are crossovers where they do other people’s jobs, but no one person does it all. Tanners would be working in the tanyard, limeyard men working in the limeyard, curriers would be staining and dressing leather and then those in the machine shop who would be splitting and shaving. Some people might do more than one of those.

• Loss of skills: Only 2 oak bark tanneries, where most of the processes are carried out by hand. Some hand processes alongside mostly machine processes in other tanneries.
• Lack of Machinery: Most of the machinery required for small scale tanneries that existed on farms was destroyed in the 1970’s as well as the lack of businesses producing machinery in the Uk. Therefore Tanneries are now having to design and build their own equipment.
• Lack of Engineers: Very few engineers now know how to repair aged machinery as well as issues with sourcing parts.
• Funding: There is a lack of funding around historic trades which makes it hard for them to keep going or for new ones to set up (expense of set up)
• Training issues:Training is done within the business, with the most experienced people training the newcomers in the various processes. Enough people (not more than two at any one time) are being trained to meet the current market. They should still be able to earn a living in twenty years time.
• Lack of Knowledge: Much of the knowledge of bark tanning disappeared due to imported materials and chemicals (pre 1930) as well as faster production demands during war time.
• Market issues:There are a lot of available markets, but someone has to go and look for them to enable the business to thrive. These include shoes, saddlery, luggage, and fashion goods. Again, company buyers need to be educated regarding quality if our production is not to lose out to cheaper machine processed leathers.
• Supply of raw materials: Local hides are used and generally the standard is quite good, although a premium is paid for selection. Materials are bought through a hide merchant, and they buy from the abattoir, and they know what is needed. The supply chain of bark to tanneries has been broken and many Forestry workers are not trained around bark harvesting systems e.g. when to harvest and how to store bark.

• Leather UK

• J & F J Baker & Co Ltd– based in Colyton, Devon. Britain’s last remaining traditional oak bark tannery.
• Peter Ananin, Woodland Tannery
• Thomas Ware & Son in Bristol do some oak bark tanning
• Jane Robertson, Oak  and Smoke Tannery

• Runcorn and District Historical Society, Notes on Leather Tanning, history and method
• J & F J Baker & Co Ltd, The Process