78 J. Waterliouse — The Application of Photor/mpjliy [No. 2, 



the name of the ' Autotype' process, it has been worked on a large 

 commercial scale for the reproduction of works of art, and is now fairly 

 beginning to come into active competition with silver-printing for all 

 ordinary purposes of portrait and landscape photography. 



On the Continent, the pigment-printing process is largely used by the 

 well-known houses of Braun and Goupil for the reproduction of works of 

 art, and is also coming into extended use for general purposes. 



Th^ following is an outline of the operations as now practised by the 

 Autotype Company. *= 



The pigment tissue is prepared by coating long bands of paper with a 

 moderately thick layer of gelatine coloured with any suitable pigment, 

 and is sold ready for use either in an insensitive or sensitive condition. 



The tissue is sensitised by immersion for a minute or two in a 5 per 

 cent solution of bichromate of potash in water, to which some alcohol may 

 be added with advantage, especially in hot climates ; the bath should also 

 be cooled down with ice if its temperature exceeds 65°. The tissue is then 

 carefully dried, and when dry is ready to be exposed under the negative. This 

 is done in a printing -frame in the usual way, the only precaution necessary 

 being to paste slips of thin grey paper round the edges of the negative, 

 so as to cut of£ a great portion of the light and form what is called the 

 * safe edge'. As the tissue generally appears black all over, the progress of 

 the printing cannot be ascertained by inspection, and it is necessary to use 

 a little instrument called an ' actinometer', by means of which, the degree 

 of exposure necessary for any negative having been once ascertained, 

 it is easy to give the same amount of exposure to successive prints. Up 

 to this point the operations are the same whatever may be the nature of 

 the support upon which the picture finally rests. The subsequent opera- 

 tions, however, differ accordingly as the image is developed on a final 

 support, by what is called the ' single transfer' method, or on a temporary 

 support, by the ' double transfer' method. In any case, some support is in- 

 dispensable to retain the image and preserve it from injury during the 

 washing. 



In the single transfer process the support is paper coated with a gela- 

 tinous substance which, though insoluble in water, retains sufficient adhe- 

 sive power when moistened to enable it to hold the picture during 

 development and afterwards permanently. 



After exposure under the negative the pigmented tissue having been 

 immersed in cold water, together with a piece of the transfer paper, the two 

 surfaces are applied to one another under water, and both drawn out together. 

 They are then laid on a zinc plate, tissue uppermost, and brought into close 



* See " The AiitoUjpe Process"^ 6th edition. Also Monckhoven's, Vidal's and 

 Liesegang's treatises on Carhon-printing. 



