INTAGLIO PROCESSES 



The best representation of the older intaglio process 

 of reproducing pictures is a steel-engraving where the 

 printing-surface is set below the surrounding portion 

 of the field, rather than the reverse as in the case of the 

 ordinary printing-block. Perhaps the best modern 

 representation of this process is what is known as the 

 photogravure. And in many respects the photogravure 

 may be said to hold the same relation to the modern 

 half-tone that the steel engraving does to the woodcut 

 of former times. 



The photogravure, like the copper and steel plate, 

 is made by digging out certain portions of the metal 

 plate, but the process of doing this is no longer a purely 

 mechanical one, modern photographic and chemical 

 methods being requisitioned for the purpose. In making 

 the plate for the photogravure a screen is used, but this 

 screen is not made of ruled glass as in the case of the 

 half-tone, but is one in which the necessary dots are pro- 

 duced by a fine layer of bitumen dust. In this process the 

 fine dots made by the bitumen dust take the place of the 

 little checks or points made by the half-tone screen. 



As a photogravure is made with a depressed printing- 

 surface instead of the ordinary raised one, a positive 

 is used for printing in place of a negative. The metal 

 plate so treated is then placed in a bath of some such 

 substance as perchloride of iron which bites out the 

 metal to the desired depth. 



The prints made by this process present a fine granu- 



