MODERN METHODS USED FOR REPRODUCTION OP PICTURES. 539 



in 1850, and was called " Gillotage," and those who worked it 

 were called " Gillotens." In 1855 M. Gillot received for his 

 discovery the reward of Honourable Mention at the Paris 

 Exhibition. 



In Zincography the zinc plate is about one-eighth of ;ui iucli thick, 

 and is either polished or grained, the picture is laid down on it, 

 with lithographic ink from transfer papei-. An acid-resisting ink 

 is then fixed on the parts of tlie plate which are to be pro- 

 tected, and the plate is then subject to the first biting in a bath 

 of dilute nitric acid, which is kept rocking so as to prevent 

 particles of nitrate of zinc being deposited on the edges of the bitten 

 parts. After a quarter of an hour the lines must be still further 

 protected. The plate is sponged, dried, and heated until the ink 

 runs and spreads over the lines. After cooling, powdered resin 

 is dusted over the surface, and the biting continued in acid 

 baths of increasing strength, when finally the plate is dried, and the 

 greasy ink is removed by benzine — a finer process. 



Photo-Zincography is the term applied to the process of trans- 

 ferring the drawing enlarged or reduced to the zinc plate by 

 photography. An ordinary negative on glass is taken of tlie 

 picture, it is applied to a sensitised zinc plate, and by the action 

 of light printed on it just as C. D. V. is on sensitised paper. 

 Zincography and Photo-Zincography reproduce only drawings 

 in line and are seldom satisfactoiy methods for portraiture; the 

 fault lies in the printing surface. 



A wood engraving of the best kind is not always perfectly level. 

 The engraver raises some parts to depress others, by this means he 

 obtains tones and a softness in one part, and a firmness and 

 emphasis in another. Now a " process " block from the very 

 nature of its production must be exactly level in its general surface. 

 The flatness of a zinco block is therefore a drawback to its ad- 

 vantages for pictorial eftect. For mechanical work the reproduc- 

 tion of architects drawings and line work it is unrivalled, and 

 the rapidity with which the blocks can l)e produced is another 

 great advantage it claims over wood engi'aving. 



A finer process is that known as — 



Daicson's Typographic Etching, in which acids are not used, but 

 a brass plate is prepax'ed with a white organic wax ground, some- 

 what as in the old form of etching. The picture is drawn on it 

 with an etching point, invented for the purpose by Mr. Alfred 

 Dawson, and which is more like a graver than an etcher's needle, 

 this cuts fui-rows in the ground, and when the drawing is made 

 the lines show the surface of the plate, the wax which remains 

 representing the future whites of the picture, between the lines 

 are the ridges of wax — these spaces are strengthened by melted 

 wax being poured on them — when the wax ground is so built up 



