330 KEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



by meaii.s of cranks, heavy hammers arc moved in penduhim fashion 

 on the hides, or in which the hammers are alternately raised ))y cams. 

 It may also be aided by using caustic soda in the tank water in the pro- 

 portion of about 1 pound to each 100 gallons of water. 



Various agencies are vised for loosening the hair, viz, putrefactive 

 fermentation; lime, either alone or in connection with caustic soda; 

 calcium or sodium sulphohydrate, etc. The first is of ancient origin, 

 and is the method even yet employed by primitive people. The green 

 hides are permitted to remain several days in a warm, moist condition. 

 Putrefaction soon begins, and quickly dissolves or destroys the epi- 

 dermis and loosens the roots of the hairs embedded in it, when the 

 latter easily slip out. This sweating process has little effect in split- 

 ting up the liber bundles of the true skin and is usually employed 

 only where a lirm, solid leather is desired, as for polishing wheels, 

 covering the Alaskan bidarkas, or more commonly in the pi-eparation 

 of sole leather, 



A more important method of removing the hair, and the one in gen- 

 eral use, is by means of a solution of lime or calcium oxide in water, 

 making a milk of lime, or calcium hydrate. This not only has a solvent 

 effect on the epidermis, but splits up the libers of -the skin, both of 

 which are essential to the production of good, pliable leather. The 

 skins are sunk flat and smooth in a tank or pit filled with milk of lime, 

 and after twenty-four hours they are removed with hooks or tongs, 

 the lime stirred up, and the skins returned, this process being repeated 

 daily for a week or ten days, or until the hair is sufficienth^ loosened. 

 The immediate effect of the lime is to swell the fibers of the skin and 

 to split them up into their constituent fibrils, the dissolving of the 

 epidermis being attributed to the action of the enzym products of 

 bacteria. In preparing leather of different degrees of solidity or 

 pliability, variations are made in the freshness and the temperature 

 of the milk of lime, fresh lime at a low temperature being used for 

 heavy leathers, while old lime at a high temperature is used in making 

 thin, pliable leathers. 



Comparative!}^ few fish skins are limed, since it destroys the fiber 

 rather than loosening it; therefore they are usually tanned without 

 liming. JShark skins, however, will go through the lime, and eel and 

 cat-fish skins may be limed for one or two days. 



On removal from the liming tank the skin is laid, flesh side down, on 

 a sloping beam having a convex surface, and scraped on the grain side 

 with a blunt knife to remove the hair; then turned over and scraped on 

 the flesh side with a sharp knife to remove all the adhering flesh, fat, 

 and other loose tissue, this process being known as "fleshing." 



Next it is necessary to remove the lime from the skin, as its presence 

 would interfere with the subsequent tannage. Also, when soft, pliable 

 leathers are desired, the swollen condition of the fiber produced by 

 the lime nuist be reduced, and in some cases a further portion of the 



