ov. 1, 1864.] THE TECHNOLOGIST. 



153 



ON CHEMISTRY APPLIED TO THE ARTS. 



BY DR. F. CRACE CALVERT, F.R.S., F.C.S. 



A Course of Lectures delivered before the Members of the 



Society of Arts. 



Lecture III. 



Leather. — The Art of the Currier. Morocco, Russia, and Patent Leathers. The 

 Art of Tawing Skins. Chamois and Glove Skins. Parchment. Hair : its Com- 

 position and Dyeing. Wool: its Washing, Scouring, Bleaching, and Dyeing. 

 Silk : its Adulterations and Conditioning. 



I shall have to crave the indulgence and patience of my audience 

 during this lecture, as it will chiefly consist of descriptions of processes 

 for the most part well known to manufacturers and others engaged in 

 the leather trade. Thus, the art of currying, which is applied prin- 

 cipally to such leathers as are intended* for the upper parts of shoes, 

 for harness, &c, is carried on at the present day nearly as it was fifty 

 years ago, and still is hut little known to the public. 



Currying. — The objects in view in currying leather are several : to 

 give it elasticity, to render it nearly impermeable, to impart to it a 

 black or other colour, and, lastly, to reduce it to uniform thickness. 

 These qualities are imparted by the following processes : After the 

 leather obtained from hides or the thicker qualities of skins has been 

 damped, it is placed on a stone surface and energetically rubbed, 

 first with a stone, then with a special kind of knife, and lastly 

 with a hard brush. The leather is then ready to be stuffed or 

 dubbed, which consists in covering it on the fleshy side with taUow, 

 and hanging it in a moderately warm room ; and as the water contained 

 in the leather evaporates, the fatty matter penetrates into the substance 

 of the leather and replaces it. The dubbing process is then repeated 

 on the other side of the leather, which is now ready to be softened and 

 rendered flexible, and this is effected by rubbing it with a tool called a 

 " pummel." The leather then undergoes the last mechanical operation, 

 which reduces it to uniformity of thickness by shaving off the inequali- 

 ties of its surface by means of a peculiarly-shaped knife called a " slicker." 

 The greatest part of the curried leather is blackened on the grain side 

 by rubbing it with grease and lamp black, and lastly brushing it over 

 with a mixture of grease and glue. I believe that some kinds of 

 curried leather are dyed by a purely chemical process, that of rubbing 

 the tanned skin, first with iron liquor, and then with a solution of gall 

 nuts or other tanning substance. The most tedious of the foregoing 

 processes is that of dubbing, which has been greatly improved of late 

 years by the Americans. The scoured skins are placed in a large 

 revolving drum, of ten or twelve feet diameter, and lined inside with 

 wooden pegs. A certain quantity of tallow is then introduced and the 



