THE RAW MATERIAL OF HEAVY LEATHERS 13 



by salting. The relative importance of these factors is not 

 yet satisfactorily determined, but cleanliness and pure salt 

 tend to eliminate the trouble. 



Drying the hides is a less satisfactory cure. The 

 principle is similar, viz. removal of moisture. Dried hides 

 are, however, much drier than salted, and are quite hard 

 and horny, hence the name " flint hides." The hides also 

 lose much weight, a considerable advantage in reducing 

 freight. Tropical hides are often flint-dry, and where 

 preservatives are expensive or unprocurable, it is often the 

 only practicable method of cure. Nevertheless, the method 

 has many serious disadvantages, and is difficult to execute. 

 If dried too slowly the hides putrefy partially ; if too quickly 

 they dry on the outside, and the interior is left to putrefy. 

 The fact that hides are of uneven thickness, and the climate 

 often hot, increases the difficulty, and often results in 

 partial destruction of the fibrous structure of the hide. 

 When dried, moreover, the hides are still subject to the 

 attacks of insect larvae, for the prevention of which the 

 usual sprinkling of naphthalene or arsenic is only an imper- 

 fect remedy. This method of cure is also a nuisance to the 

 tanner, who has to employ labour, pits and time in attempt- 

 ing to restore the hides to their original condition, and often 

 loses up to ten per cent, of the goods in so doing. Dried 

 hides are also subject to the presence of anthrax. 



Dry Salting the hides is an excellent method of curing. 

 As the name implies, it combines methods of drying and 

 salting which are used alternatively. The method is used 

 extensively in South America. A modified form of it is 

 also used for preserving the " B.I. kips," which are cured, 

 however, not with common salt, but with earth containing 

 up to 70 per cent, of sodium sulphate. Dry-salted hides are 

 largely free from the defects of dried hides, but of course 

 are more trouble to the tanner in the process of soaking 

 (see Section II., p. 16) than the wet-salted goods. 



Freezing the hides is now a commercial process. On 

 the whole the process is satisfactory, but the expansion of 

 water after freezing may tend to damage the hide fibres. 



