64 J. Waterhouse — The Application of Photogrnply [No. 2, 



rules are equally applicable, especially No. 7, and there is even more neces- 

 sity for perfect cleanliness of the paper and neatness and finish of the 

 drawing, because the faintest tints will be reproduced by the gelatine print- 

 ing surface and corrections cannot be made on it, as they can on zinc, 

 stone or copper. For this reason also, the greatest care must be taken to 

 complete the drawing in every respect before it is given to be reproduced. 

 Drawings in line may be finer and more delicate than for photolithography, 

 but still must not be so fine as to interfere with the obtaining of a perfectly 

 dense and opaque negative, otherwise the ground of the print will appear 

 dirty and stained. Pale ink may be used when necessary for effect, but 

 not more than is really requisite. Colour may be used to any extent, hav- 

 ing always due regard to the photographic effect when reproduced. On 

 account of the difficulty of photographing certain colours so as to produce 

 the same effect as in the original picture, the best results will be produced 

 from drawings specially prepared in monochrome, such as Indian ink or sepia. 



In the case of drawings for any special purpose or not intended for 

 publication, the above rules may be relaxed, but the general principles laid 

 down should be observed, as far as practicable, if the best results are 

 desired. 



When drawings are prepared specially for photographic reproduction, 

 there need be no difficulty in taking all the precautions necessary for pro- 

 ducing good results. It often happens, however, that the photographer is 

 called upon to reproduce drawings, lithographs, or old MSS., printed 

 records, or engravings, which either may never have been suitable for the 

 purpose, or, if suitable when fresh, have become dirty and stained by age. 

 Herr Scamoni, the skilful Chief of the Photographic Department of the 

 Imperial State Paper Office at St. Petersburg, has given some useful hints 

 on the treatment of such subjects under these circumstances.* 



" Yellow, or otherwise objectionable, spots should be carefully covered 

 over in the spaces between the lines with Chinese white, and whenever 

 possible the lines should be strengthened in parts where they appear weak.'* 



" Lithographs and engravings may be bleached, by immersion in a 

 solution of chloride of lime, or Eau de Javelle, (1 to 10 or 15 of water), 

 then soaked in water for some hours, after which they are treated with a 

 weak solution of hyposulphite of soda and finally well rinsed in clean 

 water." 



" Fresh grease stains may be removed with chloroform, benzine and 

 ether, or with a weak alkaline solution of caustic potash or its carbonate." 



*' Old grease stains may be removed with a more or less strong solution 

 of potash, applied at the back of the subject." 



* Handhuch der Heliographie, p. 67. 



