MECHANICS AND USEFUL ARTS. 83 



de5;i;^n ; the operation is dependent simply upon the chemic:il 

 affinity existin^: between the greasy matter employed in the ir.k 

 and that upon the stone, and the antagonism which this matter lias 

 for water, with which the stone is, in all cases, dampened before 

 pulling an impression. 



In chromo-lithography the process is identical, except that a 

 different stone is required for every color employed, and the ink 

 used is a species of oil color, similar to that adopted by artists for 

 painting. The number of stones used depends upon the number 

 of colors required, usually varying between 10 and 30, and the 

 time necessary to prepare these stones for an elaborate piece 

 of work extends over months, and sometimes years ; but the 

 number of colors in any given picture is not always an indica- 

 tion of the number of stones employed, as the colors and tints 

 are multiplied by combination in being printed one over another ; 

 thus, in an engraving where 25 stones are used there may be up- 

 ward of a hundred different shades of color obtained by this means. 

 The amount of labor and detail involved in drawing the different 

 parts of the design upon so many stones is almost inconceivable to 

 one who is uninitiated. The modus operandi is as follows : — 



Upon the first stone a general tint is laid, covering nearly the 

 whole picture, and as many sheets of paper as there are to be 

 copies of the pictures are printed from it. A second stone is then 

 prepared, embracing all the shades of some other color, and the 

 sheets already printed with the first color are worked over this 

 stone. A third, fourth, fifth, and sixth follow, each one repeating 

 the process, and adding some new color, advancing the picture a 

 step further, until the requisite number of colors have been ap- 

 plied. The printing of so many colors, and the time required for 

 drying each before the application of a succeeding one, involves 

 months of careful and anxiously watched labor. Great care and 

 skill are required to perfect what is technically termed the *' regis- 

 tering," or that part of the process which provides that the paper 

 falls upon ever}^ stone in exactly the same position relatively to the 

 outline. To attain this end, stout brass pins are fixed in a frame 

 surrounding each stone. These pins penetrate the paper in mak- 

 ing the first impression, and, the holes thus made, being carefully 

 placed over the pins in all subsequent impressions, insure the cer- 

 tainty of the outline on every stone always falling into the same 

 position on every sheet. At last, however, it leaves the press to be 

 sized, embossed, varnished, mounted, and framed. The embossing 

 is that part of the operation necessary to break the glossy light 

 and soften the hard outlines, a broken structure being given to the 

 print by being passed through the press in contact with a rough- 

 ened stone. 



Of course the chromo-lithographer and the printer must be 

 artists, in feeling at least, or they never can attain any degree of 

 competency ; and this requisite, combined with the necessity of 

 lono- study and training, is the reason why so little is done in this 

 branch of the business in this country. The number ot successful 

 chromo-lithographers, even in Europe, is yet very limited ; there- 

 fore the efforts of American houses are all the more praisewortliy, 



