880 -RErORT OF COMMISSIONER OF FISH AND FISHERIES. 



hv nutans of cranks, lioavy hammers arc moved in pendulum rashioii 

 on (li«^ hides, or in which the luuumers arc alternately raised l)y cams. 

 It may also be aided hy usino- caustic soda in (he tank water in the pro- 

 portion of al)out 1 pound to each 100 gallons of water. 



Various agencies arc used 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 tlie method even yet employed l)y primitive people. The green 

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

 Putrefaction soon ])egins, and quickly dissolves or destroys the epi- 

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

 lattei- easily slip out. This sweating process has little efiect in split- 

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

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

 covering the Alaskan bidarkas, or more commonly in the pre))aration 

 of sole leather. 



A more important mi^thod of removing the hair, and the one in gen- 

 eral use, is 1)3' 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 

 efiect on the epidermis, but splits up the fibers of the skin, both of 

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

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

 and after twenty-four hours the}' 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 sufficiently loosened. 

 The innnediate eft'ect 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 difterent degrees of solidity or 

 pliability, variations are made in the freshness and the tempei'ature 

 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. 



Comparativel}'^ few fish skins are limed, since it destroys the fiber 

 rather than loosening it; therefore they are usually tanned without 

 liming. Shark 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, flesli 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 subsecjuent tannage. Also, when soft, pliable 

 leathers are desired, the swollen condition of the fil)ei' produced by 

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



