124 ANIMAL PROTEINS 



japanning (see Part I., Section VIII., p. 76 ; and Section IX., 

 p. 86). If anything the liming should be somewhat longer 

 and mellower in order to eliminate grease, as the natural 

 grease of the hide causes the stripping of some varnishes. 

 In finishing it is important to obtain even substance, or the 

 varnish is liable to crack. Hides are soaked and sammed in, 

 and often split. Sometimes they are split twice, giving 

 grain, middle and flesh, the two former being enamelled 

 and the last japanned. Other goods are shaved very 

 smooth. The goods should be next thoroughly scoured 

 and stoned to get as much " stretch " as possible removed. 

 They are often sumached, washed in warm water, slicked 

 out again and sammed. They are then lightly buffed on 

 the grain, and after oiling lightly are thoroughly set out and 

 dried. Embossing or printing for enamels is done before 

 the goods are quite dry. Considerable difference of opinion 

 obtains as to the best oil to use in the above oiling. linseed 

 oil is widely preferred as being most likely to agree with 

 varnishes made from linseed oil. Some manufacturers of 

 japans do not dislike the use of mineral oil, but strongly 

 object to cod oil, tallow or other stuffing greases as tending 

 to cause the varnish to strip or peel. Other manufacturers, 

 on the other hand, will not have leather with mineral oil 

 in it, and indicate that nothing but cod oil should be used. 

 In all probability these various preferences are determined 

 by the nature of the varnish, which differs widely in various 

 parts of the globe. 



In this country the varnishes are made largely from 

 linseed oil by boiling it with " driers." This oil contains 

 much triglyceride of an unsaturated relative of stearic acid. 

 The double bonds are very susceptible to oxidation with the 

 production of resinous bodies of unknown constitution. 

 This phenomenon is known as " drying the oil," and has 

 been extensively used in the manufacture of linoleums. 

 The driers are either oxidizing agents or oxygen carriers, 

 such as litharge, Prussian blue, raw umber, manganese 

 dioxide, manganese borate, and " resinate." Prussian blue 

 is most preferred for British japans, as it always materially 



