SPECIAL PRINTING PROCESSES 481 



solutions, it should be well rinsed in distilled water before going from one solution to 

 the next. 



The sensitizing solution is made up as follows: 



For very soft prints: 



Solution 1 22 drops 



Solution II drops 



Solution III 24 drops 



For moderately soft prints: 



Solution 1 18 drops 



Solution II 4 drops 



Solution III 24 drops 



For average prints: 



Solution 1 14 drops 



Solution II 8 drops 



Solution III 24 drops 



For strong prints: 



Solution I 10 drops 



Solution II 12 drops 



Solution III 24 drops 



For very strong prints 



Solution I . drops 



Solution II 22 drops 



Solution III 24 drops 



Note that in each of the solutions the amount of III is always 24 drops; that the 

 sum of I and II is always 22 drops; and that increasing the proportion of II with respect 

 to I increases contrast. 



The required number of drops may be measured into a small graduate; a very 

 slight amount of shaking will mix the solutions sufficiently. The amount given — 46 

 drops — is a satisfactory quantity for an 8- by 10-in. sheet of average paper; a very 

 rough paper, such as Whatman Rough, may need perhaps 50 per cent more by volume. 



Sensitizing. — The paper to be sensitized should be cut slightly larger than the 

 negative that is to be printed — say, 10 by 12 in. for an 8- by 10-in. negative — and 

 should be pinned down on a smooth board. Guide lines may be drawn in pencil on it, 

 to indicate the exact area which is to be sensitized, but it is well to sensitize a slightly 

 larger area than that of the negative, so that the excess may be used as test slips in 

 printing. It is the writer's practice to sensitize an area 8 by 12 in. for an 8- by 10-in. 

 negative, this giving two test strips 2 by 4 in. 



The brush is wetted under a faucet of cold water and is shaken out slightly. The 

 sensitizer is then poured in a pool on the paper and is spread back and forth over the 

 paper with the brush. It is not necessary to work very rapidly, nor is it necessary to 

 be meticulous in spreading the solution evenly, as is the case in gum printing. In 

 platinum work the printing goes just as far as the light action calls for, and if there is 

 enough sensitizer in any area to take care of this light action, a satisfactory print will 

 result even though the paper may be very unevenly sensitized. However, it is well to 

 spread the solution as uniformly as is convenient. 



Brushing is continued until the paper begins to be surface dry, when the paper is 

 hung up in the dark for drying to be completed. Temperature and humidity in the 

 drying room should be such that the paper is bone dry in from 10 to 20 min., but if 

 these conditions are not obtainable, drying may be completed over a gas stove or an 

 electric plate. If this is done, care must be taken to see that the sensitizer is not 

 scorched. This will occur long before the paper itself shows any signs of scorching 

 and will result in uneven and irremovable areas of excessive darkness in the print; 

 further, this scorching of the sensitizer is not apparent until after the print is 

 developed. 



