PHOTOGRAVURE 



6 1 26 



PHOTO-LITHOGRAPHY 



skin over the surface of the print, 

 preventing access to the soluble 

 parts below it. This carbon pro- 

 cess, still largely used, is one of the 

 most beautiful photographic print- 

 ing methods. A modern develop- 

 ment of it is Ozobrome, invented by 

 Thos. Manly in 1905. In 1904 the 

 principle of the collotype process 

 was applied to the making of prints ; 

 the pigment, in the form of printers' 

 ink, was applied by hand. This is 

 the oil process, a further develop 

 ment of which is Bromoil, devised 

 in 1907 by C. Welborne Piper. In 

 both these processes the picture is 

 built up by hand application of a 

 greasy ink ; the camera supplies 

 the drawing, but the tones may be 

 largely controlled in inking. 

 Developing and Printing 



The photographer's dark-room is 

 really one illuminated by orange, 

 deep red, or dim green light, accord- 

 ing to the kind of plate handled in 

 it. Roll-film is largely developed 

 without a dark-room in tanks for 

 the purpose. While plates can be 

 treated on a similar system, they 

 are commonly developed in a 

 " dark-room " in shallow open 

 dishes, or in grooved tanks. 



Plates are next " fixed " in a 25 

 p.c. or 30 p.c. solution of hypo for 

 rather longer than is required for 

 the semi-opaque white emulsion 

 left undarkened by the developer to 

 dissolve, and the clear negative is 

 then washed in clean water for 

 about an hour, to remove the 

 hypo, "and is put to dry. 



In making prints from negatives 

 the materials most used are 

 bromide and gaslight papers on 

 account of their manipulation 

 throughout by artificial light. 

 Photographs made on these papers 

 are of cold black " colour," but 

 by subsequent treatment can be 

 toned brown, sepia, red, blue, 

 green, and other colours. The 

 papers themselves are made hi a 

 wide range of surfaces from glossy 

 to others resembling canvas. 



The platinum and carbon print- 

 ing processes are less generally used, 

 although they yield the very finest 

 forms of photograph. Platinum 

 prints may be either black or sepia, 

 but the carbon process allows of 

 any colour of print being made. 



Bibliography. Instructions in 

 Photography, W. de W. Abney, 

 llth ed. 1905 ; A Primer of Photo- 

 graphy, O. Wheeler, 1910 ; Photo- 

 graphy of To-day, H. C. Jones, 1913 ; 

 Dictionary of Photography, 10th 

 ed , E. J. Wall, 1920. 



Photogravure. Photo-mechan- 

 ical process of making printing 

 plates, known also as intaglio or 

 rotogravure. In photogravure the 

 shadows of the original are repre- 

 sented by cavities in the printing 

 surface, and the light portions by 



the bare metal. The image of the 

 original is etched into the plate, 

 the deepness of the etching varying 

 with the depth of tone of different 

 parts of the original. When an 

 impression is taken, the ink is with- 

 drawn by the paper from the re- 

 cessed parts of the plate by pressure. 

 Photogravure possesses a soft- 

 ness of tone superior to the usual 

 newspaper illustration reproduc- 

 tions known as half-tone, with 

 which it is competing success- 

 fully ; it is much used for editions 

 de luxe. When wood-engraving 



reached the highest point of com- 

 mercial development, the half-tone 

 block supplanted it by reproducing 

 the original subjects more faith- 

 fully and more quickly. In turn, 

 photogravure and photo - litho- 

 graphy are superseding the half- 

 tone block by reason of the artistic 

 results attained. A notable appli- 

 cation of photogravure was seen 

 in the illustrated supplement 

 added to The Times weekly edition 

 in 1920. See Half-tone ; Intaglio ; 

 Lithography, col. plate ; Printing ; 

 Process. 



PHOTO-LITHOGRAPHY 



A. B. Blayney, of The Amalgamated Press, Ltd. 

 This article is one <>/ a group dealing with illustrations for periodicals 

 of all kinds. See Colour Printing ; Half-tone ; Intaglio ; Litho- 

 graphy, with colour plate ; Offset ; Photography ; Printing ^ Process 



Photo-lithography is a method 

 of reproducing a subject photo- 

 graphically on to a flat surface 

 from which the subject can then 

 be printed lithographically. The 

 fundamental difference between it 

 and chromo-lithography is that 

 most of the hand drawing described 

 under the latter heading is almost 

 eliminated, being brought into use 

 only for touching up or improving 

 the functions of the camera. One 

 method is to take a negative of 

 the subject and print it upon 

 sensitised transfer paper which has 

 been coated with gelatin ; after 

 exposure, the print is rolled with 

 transfer ink and dipped in water, 

 which absorbs the gelatin, allow- 

 ing the ink to be removed where no 

 photographic print was made. The 

 transfer is impressed on to a 

 printing plate, which can be dupli- 

 cated in sets by transferring on to 

 the machine plate. This method is 

 largely adopted for the reproduc- 

 tion of subjects which have been 

 drawn in straight or curved lines, 

 dots and grain, and is used in the 

 execution of auctioneers' plans, 

 railway maps, and, being photo- 

 graphic, the original subject can 

 be reduced or enlarged. 



Photography on Metal Plates 



A later development is by photo- 

 graphy direct on to the printing 

 plate. This is akin to the 3- or 4- 

 colour half-tone relief process, but 

 printed from a flat surface. The 

 advantages are the elimination of 

 stereotypes and the substitution of 

 a cheaper paper for the expensive 

 glazed variety required by the 

 relief method, and with no de- 

 traction from the ultimate result ; 

 in fact a more faithful reproduction 

 is attained. 



Direct photo-lithography is now 

 applied to the reproduction of fine 

 colour-prints, magazine covers and 

 works of art, for all of which it is 

 superseding chromo-lithography. 



The original painting or sketch is 

 placed before the camera and a 

 negative secured through a sheet of 

 lined or dotted glass (termed a half- 

 tone screen) interposed between 

 the sensitised plate and the lens, 

 the colours of the painting being 

 extracted from each other through 

 colour filters. Thus, when a 

 picture as represented by the 

 subject on the unglazed side of 

 the coloured diagram facing page 

 4916 is to be reproduced in several 

 colours, original negatives of each 

 of these colours are made, and the 

 work of the camera is enhanced 

 by touching up by hand where 

 necessary. These colours are 

 transferred photographically from 

 the negatives to the same number of 

 lithographic master printing plates, 

 one colour only on each, these 

 plates being proofed, and tested 

 progressively in the same way as 

 a chromo-lithographic print, to 

 reproduce a replica of the original 

 painting. 



In practice it has been found 

 that while the original photo- 

 graphic lithographic plate gives a 

 perfect reproduction if printed 

 from direct, the detail and sharp- 

 ness become blurred if duplicated 

 by hand transferring as applied to 

 chromo-lithography. A revolution- 

 ary method enables the image to be 

 photographically duplicated into 

 perfect register on to the machine 

 plate direct from the one negative, 

 the operation being repeated so 

 that there may be 16, 32, or more 

 sets of the same subject on a 

 machine plate, each set virtually 

 an original, and equal to the 

 master plate. 



The negative is placed hi a dupli- 

 cating machine which reproduces 

 the image of the negative in the 

 exact position required on to a 

 sensitised machine plate, say 16, 

 32, or more times as the case may 

 be. One set will be secured on each 



