io 4 ANIMAL PROTEINS 



The bags are then placed into a vat of warm sumach liquor, 

 in which they just float. The bags are pushed down and 

 the liquor stirred up, so that the goods are in constant 

 motion. After a few hours they are piled on a rack, and 

 the tan liquor of the interior is caused to diffuse through 

 the skins by the pressure due to the weight of the pile. 

 The bags are refilled with fresh and stronger sumach liquor 

 and the process is repeated. The skins are thus lightly 

 but effectively tanned in about 24 hours, and the leather 

 has very fine grain and soft feel. However tanned the skins 

 are dried out after tanning, and sorted in the " crust " 

 according to size and colour. The larger skins are preferred 

 for upholstery and the smaller for fancy goods and book- 

 binding. 



To illustrate the course of finishing operations, the case 

 of hard-grain morocco for bookbinding may be given as 

 typical. The goods are wet back with warm water and 

 drummed for 1-2 hours in warm sumac to prepare for 

 dyeing. They are then struck out by machine, sammed 

 and shaved. Dyeing follows, with acid colours, in a drum. 

 The goods are run first in a little water and the dyestuff 

 added very gradually through a hollow axle. The acid 

 required (preferably formic) is added later to develop the 

 full shade. Warm solutions are used, and the dye bath is 

 practically exhausted. The goods are next placed in cold 

 water to wash off superfluous liquor and free the skins from 

 acid. They are then horsed to drain, struck out and hung 

 up to samm. They are seasoned with milk and water and 

 piled to temper. They are " tooth rolled " in the glazing 

 machine two ways : right -hand shank to left fore shank and 

 vice versa, and piled again. After wetting back again they 

 are " wet grained " by hand with a cork board in four 

 directions : belly to belly, shank to shank, and across as 

 before, and finally from neck to butt. They are immediately 

 hung up in a warm shed to dry, and to fix the grain. They 

 are then softened by " breaking down " with a rubber board, 

 top seasoned, piled to temper and dry, brushed lightly, piled 

 again, brushed more heavily, and dried out. They are 



