Comprehension: Tanning in Nigeria Today (I)

The tanning of hides to make leather is a craft that has been practised by Nigerians since time immemorial. No sooner had this thought struck me on a visit to Kano than I decided to see how it is done nowadays in a modern tanning factory.

First, the dry skins are taken to the soaking yard. Once there, are thrown into huge water pits each capable of holding 475 kg of goat skins. Then, insecticides, fungicides and bactericides have been added to the water, and the skins are soaked for three and a half hours. During this process, they become, of course, completely “rehydrated”.

Following that, they are put into large wooden drums for limiting in order to get rid of the hair. Slaked lime and sodium sulphide are used for this, the former swelling the skin, the latter removing the hair. The skins, chemicals and water having been put in, the drums revolve, first of all for thirty minutes, and then for ten minutes every half hour for the next ten to fifteen hours.

Removed from the drums, the skins go next to the fleshing machine, as any remaining hairs on them must now be removed. This machine consists of a large roller containing a revolving knife. Once this stage has been completed, the skins are again thrown into water and put through the next stage called scudding, in which any tiny hairs still adhering to the skin are removed. No machine is, as yet, used for this part of the process, which is carried out by men in rubber aprons and gloves; each man places a skin on a curved, sloping board in front of him and then, while holding it in position by leaning on it, scrapes the skin with a large knife.

Once this is done, the next step must be to reduce the alkalinity since, because the skins were earlier soaked in line, they are now very alkaline. This is done with water and ammonium sulphate, in the same type of drum that I mentioned previously. The drums are turned for twenty to thirty minutes before an enzyme is added which removes all wrinkles and scars from the skin, softens it and makes it permeablePermeability is a measure of the ability of a porous material (having small spaces or holes through which liquid or air may pass) to allow fluids to pass through it. More to air. After the addition of enzymes, the drum is rotated for a further period of thirty minutes.

(NOSEC Book 4, page 15, UPPLC)