66 ANIMAL PROTEINS 



used as usual, the hides may be thrown into water from 

 ioo-io5 F., and will be ready for depilation in 7 or 8 

 hours. 



Even a stronger liming may be given, especially if the 

 soaking is unusually prolonged. Such processes undoubtedly 

 save hide substance, and the pelt is obtained more free from 

 lime, but they have the disadvantage that the natural 

 grease of the hide is only imperfectly " killed " (i.e. saponi- 

 fied or emulsified), and may interfere with the normal 

 course of the tannage. The plumping is also apt to be 

 insufficient. On the other hand, liming processes are also 

 used in which a mellower liming or a longer liming is preferred 

 in order to produce the desired degree of softness and 

 pliability in the finished leather. Belting must not be too 

 soft, of course, and it will be clear that the required differ- 

 ence from sole leather can be produced either in liming or 

 tanning or partly in both. These considerations also 

 decide whether bating is to be omitted or not. A hard 

 astringent tannage in sour liquors after a sharp liming 

 might make bating essential, but in these days it is usual 

 to avoid it and produce the effect in other ways. A light 

 bating of a few hours is sometimes given, but it is more 

 unusual to delime the grain thoroughly with boric acid, 

 using up to 20 Ibs. per 100 butts. Crackiness is a fatal 

 defect in strap butts, so that a sound grain must always be 

 obtained. Generally speaking, therefore, strap butts receive 

 more washing in water, and rather more deliming than sole 

 leather, even when they are not bated. It is also usual to 

 scud much more thoroughly, and to round a larger propor- 

 tion of butt, especially in length. 



The tannage is usually carried out with a blend which 

 includes a much greater proportion of the fruit tans, and 

 correspondingly less of extract. 



Distinctly more myrabs are used than in sole leather 

 tannages, in the dry material, and amongst the extracts 

 chestnut is preferred to quebracho, and myrabs to mimosa 

 bark, though all these may be used in some degree. In the 

 past the most favoured extract has been undoubtedly 



