LIGHT LEATHER MANUFACTURE 95 



fairly successfully by artificial methods. " Erodin " (Wood, 

 Popp and Becker) involves the use of B. erodiens and a suitable 

 culture medium including organic deliming salts : " Oropon," 

 "Pancreol" and others involve the use of ammonium 

 chloride and trypsin, together with some inert matter. 



Ivight-leather goods are usually drenched after puering. 

 They are also often split green after the wet work. Sheep- 

 skins thus yield " skivers " (the grain split), whilst the flesh 

 split is often given an oil tannage (see Part IV., Section III.). 

 The greasy nature of sheep and seal skins necessitates the 

 processes of " degreasing." In the case of sealskins this 

 is done largely before liming, but with sheepskins either 

 after being struck through with tan, or after tannage is 

 complete. Sheepskins are often preserved in the pelt by 

 pickling with sulphuric acid and salt, which process forms a 

 temporary leather. The fibres of the pelt are dried in a 

 separate condition, but the adsorption is easily reversible 

 and the pelts may be " depickled " by weak alkalies and 

 afterwards given an ordinary vegetable tannage. 



In the vegetable tannage of skins for light leathers, the 

 same theoretical considerations have force as in the heavy - 

 leather section, but the former has its own rather special 

 requirements and aims. Generally speaking, a softer and 

 more flexible leather is required, but these qualities must 

 not be imparted by stuffing with grease as in the currying 

 of dressing leather, because a bright and grease-free result 

 is usually required. Hence it is important that a sweet 

 mellow tannage be given. The durability of the leather is 

 also a primary consideration for goods intended for book- 

 binding, upholstery, etc., and the tannage must be arranged 

 to impart this quality and avoid anything tending to cause 

 the perishing of the fibre. Thus oak bark is a popular tanning 

 material, and sulphuric acid very definitely avoided. The 

 tannage must be fast, and take the dyestuffs well, and for 

 the production of light shades of colour in dyeing must be 

 a light-coloured tannage. All these qualities are imparted 

 by sumach, which also fits in excellently with the other 

 general requirements, such as softness, brightness and 



