232 



TABLES 218-223.— PHYSICAL PROPERTIES OF LEATHER * 



Most physical properties of leathers not only depend on the kind of skin 

 and method of tannage but also vary widely from one hide to another of the 

 same kind, from one location to another within the same hide, and in local 

 random fashion. For example, the tensile strength of vegetable-tanned cattle 

 hides shows coefficients of variation of 6 percent among bends (from different 

 hides), 9 percent among locations (within a hide), and 11 percent for local 

 random fluctuations. 05 The Federal Specifications Board in the United 

 States requires that at least 7 pieces of leather be sampled for most physical 

 tests. 00 In any use of a physical property of leather, such as designing an 

 experiment or acceptance testing for commercial purchase, these variations 

 and the consequent statistical precautions must be observed. The figures below, 

 then, are illustrative, not precise values for any given type of leather. 



* Prepared by R. Hobbs, National Bureau of Standards. 



65 Beek, J., and Hobbs, R. B., Journ. Amer. Leather Chem. Assoc, vol. 36, p. 190, 1941. 

 6« F e d era i specification for leather and leather products, Kk-L-311. Government Printing 

 Office, Washington, D. C, March 1945. 



TABLE 218.— TENSILE STRENGTH AND ELONGATION OF LEATHER 



Elongation, percent 



Thickness 

 Kind of leather 1/64 in- 

 Belting, vegetable-tanned steer 11 



Calfskin, chrome-tanned 3 



Calfskin, vegetable-tanned 3 



Cordovan, horsehide butt 3 



Deerskin, chrome-tanned 5 



Garment, chrome-tanned horse 4 



Kangaroo, chrome-tanned 2 



Kid, chrome-tanned 2 



Sheepskin, shearling 3 



Shoe upper, chrome retan 6 



Sole, vegetable-tanned steerhide 13 



67 Wilson, J. A., Modern practice in leather manufacture, Reinhold Publishing Co., New York, 1941. 



TABLE 219.— DIFFUSION CONSTANTS OF WATER VAPOR THROUGH 



LEATHER, AS FRACTIONS OF THE DIFFUSION CONSTANT 



THROUGH AIR (20°C) fl8 



Heavy Glove Patent Vegetable-tanned 



chrome upper Box calf capeskin leather insole 



.1-2 21-26 .17-26 .004 .09 



88 Progress in leather science, 1920-1945, British Leather Manufacturers' Res. Assoc, London, 1948. 



SMITHSONIAN PHYSICAL TABLES 



