MECHANICS AND USEFUL ARTS. 97 



influences the commercial value of all discoveries. Respecting the litho- 

 graphic method, the whole expense may be said to be that of printing oflf 

 the impressions, as the cost of materials for one transfer of a leaf on to the 

 stone is less than one half-penny, and the time necessary for producing the 

 original figure on the stone is a few minutes. Both the other modes are 

 about as speedy, with the exception of the etching, which, occupying rather 

 more time, hence involves a little more labor and expense, which is, how- 

 ever, more than compensated for in the process of printing from raised cop- 

 per figures, as the expense of printing off impressions is in this case ex- 

 tremely small, owing to the durability of the blocks employed, the most 

 expensive form of the process must be below that of the process at present 

 employed. 



ON AN IMPROVED METHOD OF PREPARING PRINTING SURFACES. 



This invention, by M. M. Chevalier and O. Sulivan, of Paris, has for its 

 object to obtain printing surfaces as a substitute for lithography and other 

 similar methods of printing, the use of which, besides being much cheaper 

 than lithographic printing, offers this advantage, that a design consisting of 

 a number of different colors can be printed at one and the same time ; while 

 in ordinary printing each color has to bo worked off separately, and entails 

 a great amount of labor. 



In carrying out the invention, the patentees take any suitable permeable 

 substance or fabric, such as linen, calico, cloth, canvas, or other woven or 

 suitable material, or, it may be, a reticulated metal surface, or metallic plate 

 or sheet, perforated with minute holes to impart the required degree of 

 permeability, and ou this surface they draw or write the desired figures or 

 characters in an ink composed of lamp-black, Indian ink, gum, sugar, and 

 salt. 



A coating of this ink being applied to the permeable surface in the form, 

 of the design or character or characters required, they next coat the permea- 

 ble substance, on the side drawn upon, with a thin coating or film of gutta- 

 percha or of gelatinous material, covering the drawing as well as the other 

 part of the permeable material. When the coating of gutta-percha or other 

 gelatinous material is dry, the fabric, or other surface, so coated, is washed. 

 The gutta-percha or gelatinous materal, at that part where it comes in direct 

 contact with the permeable material, adheres firmly thereto ; but at those 

 parts covered by the ink, it has no such adhesion, and simply holds to the 

 ink design. The ink, being readily soluble in water, is removed in the 

 washing, and carries away the gutta-percha covering it ; thus the design 

 drawn upon the permeable material is now the only pervious part remaining 

 in the surface. 



The back part of the pervious substance or fabric is now to be coated with 

 the ink or color or colors required to be printed ; and the ink or color having 

 been applied, the impression is taken from the face of the fabric or substance 

 by pressure in a suitable press ; the paper or surface to be printed being 

 placed in contact with the face of the fabric or printing surface, the ink or 



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