52 ANIMAL PROTEINS 



edge. This hand process, which demanded considerable 

 skill, is fast becoming extinct, and machine shaving is 

 already almost universal on account of its greater speed. 

 The machines consist essentially of two rollers, one of which 

 is smooth, whilst the other is a spiral knife-blade cylinder 

 (cp. Section II., p. 23). The sarnmed goods are held in the 

 hands and placed over the smooth roller, which is raised 

 to the cutting roller by a foot treadle. A number of similar 

 operations (" flatting," " whitening," " buffing ") are 

 carried out by a suitable change of tool. In all these 

 operations good samming is important. 



Splitting is another important operation on tanned 

 leather. In this process the leather is cut parallel to its 

 grain surface, thus yielding two pieces with the same area 

 as the original, the " grain " and the " flesh split." It is 

 essentially a machine operation, and is carried out by 

 presenting the carefully sammed leather to a sharp knife- 

 edge, towards which it must be constantly pressed. The 

 " band knife " machine is the most popular arrangement. 

 The knife is an endless belt, which continually revolves 

 round two pulley wheels of equal size. In between these 

 the knife is horizontal, and is then used for splitting. The 

 sammed leather is pushed towards the blade by two feed 

 rollers, and the grain passes above the knife on to a small 

 platform, whilst the flesh or " split " passes below and 

 falls to the ground. Emery grinders and thick felt cleaners 

 in the lower part of the machine keep the knife in good 

 condition. The adjustment of the machine is delicate and 

 requires considerable experience. With care splits may be 

 obtained down to j 1 ^" thick, and sometimes as many as 

 6 or 7 splits are obtained from one hide. 



Oiling is still usually done by hand, and cod oil is still 

 preferred for many classes of goods. Of recent years there 

 has been a great extension of the use of sulphonated oils, 

 which have the valuable property of forming an emulsion 

 with water or tan liquor. With these materials it is easier 

 to ensure the goods being completely covered with oil. 

 The penetration of the oil into the leather is also quicker 



