FAT TANNAGES 179 



attempt is made to dry the fibres separately in an " un- 

 tanned " condition, and to coat them simultaneously with 

 fat so that a permanent leather is obtained. It is only 

 possible to do this, if the pelt is constantly during drying 

 subjected to mechanical working, e.g. by twisting, folding, 

 bending, drumming, staking, etc. The resulting leather is 

 often called " rawhide leather," and presents a real advantage 

 over other leathers in its great tensile strength. Where 

 toughness is an essential quality, there is much to be said 

 for the fat tannages. It is also possible, of course, to effect 

 compromises between ordinary tannages and the straight 

 fat tannages ; thus picking band butts, which must be 

 tough, are often very lightly tanned with oak bark or 

 chrome, and then given what is practically a heavy fat 

 tannage. In the most typical of fat tannages, moreover, 

 it is often common to " colour " the goods by a brief immer- 

 sion in a weak vegetable tan liquor. Further, the employ- 

 ment of fats in the currying of dressing leather is in effect 

 a fat tannage superimposed upon the vegetable tannage. 

 (See Combination Tannages, Section VI.) 



The fat tannage is undoubtedly one of the earliest 

 methods for making leather. Prehistoric man discovered 

 that the skins of animals killed in hunting could, by alter- 

 nately rubbing with fats and then drying slightly, be 

 eventually converted into a useful leather, whereas without 

 the fat it was stiff and horny. Even yet similar methods 

 are in use, thongs of raw hide being continually twisted during 

 drying, with intermittent application of fats. 



In the modern fat tannages drums are used to give the 

 necessary mechanical working to the goods. The raw hide 

 leather produced in the U.S.A. is made by drumming the 

 nearly delimed goods with tallow and neatsfoot oil. In this 

 country the fat tannages have been typified by the " Crown " 

 and " Helvetia " leathers. The hides are thoroughly limed 

 in mellow limes, and after the beam work are delimed by 

 drenching, scudded, and sometimes fleshed again, and then 

 coloured off in tan liquor. After partial drying, they are 

 drummed warm for some hours to ensure isolation of he 



