156 Lithographic Process. 



LITHOGRAPHIC PROCESS. 



[From Senefelder's Course of Lithography.] 

 In the chemical or lithographic process of printing, it matters 

 not whether the lines he engraven or elevated ; but they must be 

 covered with a liquid to which the printing ink, consisting of a 

 homogeneous substance, will adhere according to chemical affi- 

 nity and the laws of attraction, while at the same time all those 

 places which are to remain blank, must possess the quality of re- 

 pelling the printing ink. Now all greasy substances, or such as 

 are easily soluble in oil, will not unite with any watery liquid. That 

 principle is the foundation of this new art. It is not sufficient 

 however to make certain spots of the plate greasy, and others 

 wet ; water, generally speaking, not having power sufficient to 

 repel the printing ink from the places on which it ought to be. 

 It is necessary therefore to |)repare the surface of the plate, so 

 that in those places which are to remain black, it may reject the 

 printing ink, as if from aversion. 



Among the different materials applical)le to this new method 

 of printing, the calcareous slate occupies the first place. It pos- 

 sesses not only a strong tendency to combine with unctuous sub- 

 stances, and to retain them obstinately, but it likewise possesses 

 the ])ower of absorbing bodies of a different nature, such as aque- 

 ous fluids ; and, thus impregnated, will repel oleaginous and 

 unctuous bodies. The best stone of this description is that pro- 

 cured from Solenhofen, in the district of Manheim, three leagues 

 from tiie town of Neijburg. In general the proper thickness of 

 a plate of it is from two inches to two inches and a half; and, 

 provided their surface l)e uniform, the harder sorts of stones are 

 the best for all the manners of lithography. They require to be 

 carefully polished : first with pumice-stone and v.ater, until the 

 edge of a ruler applied in all directions every where touches 

 the surface ; the stone is then (having been placed horizontally) 

 to be thinly covered with fine sand, mixed with a spoonful of wa- 

 ter, to which a little soap may be added ; another stone is then 

 to be put on the surface, and moved up and down in different 

 ways ; at intervals, fresh sand and water must i)e applied ; and 

 thus two stones are at the same time polished and rendered per- 

 fectly level. 



The next important requisite for lithography is the chemical 

 ink to draw or write with. The principal qualities of this ink are 

 — its filling the jiores of the stone in those ])laces to which it is 

 applied with an oily, greasy substance, and its capacity of resist- 

 ing the action of atiuafortis and other acids. M. Senefelder com- 

 municates a variety of recipes for this ink. We transcribe one. 

 Wax (by weight) 2 parts ; shellac 4 parts ; soa]) (the common 

 kind, prepared from tallow and soajj lees) 4 parts ; lamp-black 



I part. 



