SPECIAL PRINTING PROCESSES 483 



the quantity of this chemical to use since this depends on the balance between printing 

 time and contrast desired. However, a lump the size of a large pea in 32 oz. of devel- 

 oper will have a marked effect, and even greater amounts may be used. If this 

 modification is carried too far, the prints will have a granular appearance. 



With any given sensitizer, the use of a hard-surfaced paper gives more contrast 

 than a softer, i.e., a more absorbent, one. This is due apparently to the fact that the 

 harder paper requires longer printing in order to keep the sensitizer on the paper in the 

 lighter areas, and while this longer printing is taking place, the shadows, of course, gain 

 in depth. This fact may be used to advantage when printing from a soft negative 

 and should, of course, be allowed for in any case when adapting the sensitizer to the 

 negative and to the desired result. 



Decreased Contrast. — If the prints have too much contrast even when the softest 

 working sensitizer is used, softer effects may be obtained by the addition of a very 

 small amount of hydrochloric acid to the developer. Again, it is impossible to say 

 precisely how much to use, but a perceptible effect will result if a finger is dipped into 

 the 1 to 60 clearing bath, and the adhering acid is stirred into the tray of developer. 



Another method for diminishing contrast is to print lightly and heat the developer, 

 though here also the balance must be determined by circumstances. In extreme 

 cases, the writer has developed prints at 200°F., but this is rarely necessary, about 

 150°F. being the ordinary limit. It should be noted that a warm developer not only 

 cuts down contrast, but also gives warmer tones in the finished print. 



Colder Tones. — Blue-black tones may be secured by using a developer made up as 

 follows : 



Water, warm 1000. cc. 48 oz. 



Potassium oxalate 180.0 g. 9 oz. 



Monobasic potassium phosphate 60.0 g. 3 oz. 



This must be used cool, i.e., not above 70°F. 



Warmer Tones. — A warm black or even a brown tone may be obtained by using a 

 hot developer, as described above. If still more warmth is required, it may be 

 obtained with normal printing time by the addition of mercuric (not mercurous) 

 chloride to the developer. The amount to use must be decided by the worker, but 

 60 gr. per 32 oz. (4 g. per liter) of developer will have a decided effect. It should be 

 noted that mercuric chloride (which is also known as bichloride of mercury and 

 as corrosive sublimate) is a dangerous poison and should be handled carefully. 



Multiple Printing. — If, through the softness of the negative or because of incorrect 

 choice of a sensitizing mixture, the print lacks the desired contrast when finished, 

 more strength may be given it by sensitizing and printing a second time. The 

 sensitizing may be carried out exactly as at first, and printing maj^, of course, be either 

 full or partial; i.e., a comparatively light printing may be given, merely to add weight 

 to the shadows, or the second sensitizing may be printed to the same depth as the first, 

 when all the gradations will have a weight equal to the original added to them. 



No special method of registration is needed as with multiple printing in carbon and 

 gum. The sensitized print is simply placed on the negative in the printing frame and 

 moved about with the fingers until it is in register, this point being clearly visible if 

 the negative and print are viewed by strongly concentrated transmitted light. It may 

 be that the first processing has caused the print to shrink so that perfect registration 

 cannot be obtained; in this case the worker must use his own judgment as to whether 

 to split the difference through the entire print or to register certain portions — say, 

 the eyes in a portrait — and let the rest of the picture be out of register. In any case, 

 the difference is not likely to be great enough to be objectionable for pictorial 

 work. 



