158 ANIMAL PROTEINS 



and pumped to other drums, the once-used liquor to a 

 drum containing goods already treated with a twice-used 

 liquor ; the twice-used liquor to a drum containing green 

 goods, and the thrice-used liquor pumped to the drain. 



In any of these methods the chrome alum liquor is 

 suitable, using 10 per cent, alum and 3 per cent, soda on 

 the pelt weight. The glucose liquor has also proved very 

 suitable for chrome calf, and the liquors made with sul- 

 phurous acid or its salts have increasing popularity on 

 account of lower costs. Many tanners use bought liquors 

 " chrome extracts," which are supposed to be specially 

 devised to suit the tannage of chrome calf. When 

 thoroughly tanned through, as can be readily judged from 

 a sectional cut of the leather, and also by the strength of 

 the liquor remaining, the goods are horsed in pelt overnight, 

 and are then ready for finishing. 



In finishing box calf the neutralization should be 

 thorough, or the acid may cause trouble in dyeing and 

 fat liquoring. Imperfect removal of excess chrome salts 

 may cause the formation of " chrome soaps," which are 

 very difficult to remove ; the goods should therefore be 

 well washed. There are two general types of treatment 

 before blacking. In one, the skins are first well washed 

 with water at 110 F., neutralized with about 3 per cent, 

 borax, and well washed again. Striking follows and is 

 usually very thorough, partly because it assists in pro- 

 ducing evenly the characteristic box grain, and partly 

 because the finished leather is sold by the square foot. 

 Machine striking is now almost universal, and may be done 

 several times at different stages in the drying. When 

 half dry (" sammed ") the skins are shaved by machine 

 and, at this stage usually, weighed. Dyeing and fat 

 liquoring then follows. In the other type, the goods are 

 merely washed, and then struck out, sammed, shaved and 

 weighed. The skins are then neutralized, washed and 

 immediately dyed and fatliquored. The advantages of 

 this latter course are that the goods remain in the drum 

 for the last four processes, which is economical of labour, 



