MANUFACTURE OF LEATHER FROM MARINE SOURCES 547 



They are tanned by either the chrome or vegetable process, depending upon the 

 use intended. In many instances the heavy keratoid portion of the hide, down 

 the center of the back, is removed when the hide is made into leather. In the 

 younger alligators this portion is used for decorative purposes after it has been 

 softened by the tanning process. Alligator hide leather is increasing in value as 

 a result of the reduction of the population by intensive hunting, and the drainage 

 of many swamp areas, 



Food-Fish Skins. As in the case of sharkskins the value of a hide is based to a 

 considerable extent upon the size of the skin. This alone eliminates the wide 

 usage of the skins of food fish, although they are used to some extent in the 

 manufacture of novelties, ladies' shoes, and decorations for handbags, etc. 



The skins of several species of large fish are those generally tanned. These 

 include cod, salmon, red snapper, grouper, and halibut. The chrome process is 

 generally used since it produces a softer, more pliable leather than any of the 

 vegetable tannins. The skins can be dyed almost any color desired, and have 

 an attractive natural design on the surface resulting from the removal of the 

 scales from the follicles. 



The tanning operation is somewhat simpler than for shark and similar skins 

 and sealskins. The scales are first removed. If the hides have been cured by salt- 

 ing, they are soaked in a series of fresh-water baths to remove the salt. The 

 liming treatment is not generally necessary since there is no hair to remove, but 

 a sodium carbonate bath is used to saponify a portion of the oil or fat usually 

 found in small amounts in the skin. The sodium carbonate treatment also "plumps" 

 the skins so that they swell and absorb the tannin more readily. In some cases 

 both lime and sodium carbonate are needed to accomplish the desired results. 

 Bating and tanning are accomplished by either the vegetable or chrome methods 

 as described later in this chapter. 



Salmon Skins. One large canning firm in the Pacific Northwest has devised 

 a machine for removing the skins of salmon prior to canning. This machine is 

 constructed so that the skins are removed in one large piece without injury. 

 Salmon skins are much heavier than those of many other species of fish and are 

 suitable for use in the leather industry without the reinforced backing required 

 when lighter skins are used. The skins are large enough for tanning to be economi- 

 cally feasible, and they are naturally decorated by the pattern resulting from the 

 removal of the scales. These skins have been tanned by both the chrome and 

 vegetable methods. It is possible that in the future salmon skins may become a 

 large source of leather material. 



Fish Intestines and Stomachs. The large intestines of the whale have been sug- 

 gested as a source of leather. Considerable work on this material has been carried 

 out by various investigators, and the results obtained indicate that it may be used 

 to advantage for certain purposes. The intestines of the porpoise have also been 

 investigated, and from them it has been possible to produce a very satisfactory 

 substitute for catgut, used in producing surgical sutures and for musical instru- 

 ment strings. Some work has been done upon shark stomachs, but nothing definite 

 has yet been accomplished. Shark and ray tubes, however, have been tanned, and 

 the resulting leather has been shown to be of commercial values, though not used 

 at present. 



