8o ANIMAL PROTEINS 



used in weak liquors. The hides, moreover, are completely 

 delimed, and there is little danger of bad or uneven colour. 

 Tanning under these conditions is at its easiest ; it is almost 

 more difficult to spoil the goods than make them right. 

 Under such conditions tanning deteriorated rather than 

 improved in method. When neglecting it made little 

 difference to the finished leather, it was neglected. 



This state of affairs, however, was embarrassing when- 

 ever a tanner wished to try any other tanning material. 

 The expense of gambier and oak bark made valonia and 

 mimosa bark into obviously desirable alternatives and 

 substitutes. Methods which would tan with gambier, 

 however, would not work with Natal bark or valonia, and 

 many a tanner has had to revise his method of tanning 

 from end to end. The use of myrabs also raised the problem 

 of souring, and it has become evident that " working the 

 liquors down the yard " is as desirable a method for dressing 

 leather as after all other tannages. It will be clear from the 

 above that types of upper-leather tannages are less typical 

 than for other leathers, but nevertheless the more progressive 

 manufacturers have for some years now been working 

 on sounder lines, economically and scientifically. In 

 such cases it is now usual to pass the goods through at 

 least two sets of handlers, and through liquors of gradually 

 increasing strength. Occasionally dusters or layers are 

 given, especially for the heavier goods. The tannage 

 is nearly always commenced now by paddling the goods in 

 the oldest liquor. This paddling may be anything from 

 half an hour up to twenty-four hours. It is sometimes 

 desired to work up a " grain," and the old liquor is then 

 often sharpened by the addition of fresh gambier or leach 

 liquor. 



The same tendency to save labour in handling is to be 

 observed in upper leather tannages as in sole and other 

 dressing leather factories. There is also a tendency to obtain 

 rather more weight in tanning by using stronger liquors, 

 and in the heavier goods to shorten somewhat the time taken. 

 The following methods may be taken to illustrate modern 



