SPECIAL PRINTING PROCESSES 479 



Variations in total contrast are very easily obtained. Almost any degree of 

 , contrast may be secured by altering the composition of the sensitizer, and still further 

 variations are possible through varying the constitution of the developer. 



Almost any paper support may be used. This makes possible the use of very 

 beautiful cliarcoal and drawing papers, as well as of vellums and tissues, so that widely 

 varying effects may be obtained by this means. 



A range of colors from cold and neutral black through gradually increasing warmth 

 of brown, even to sepia and red, is easily secured by slight changes in the developer. 

 Further, these colors do not involve any loss of permanence, as is often the case in the 

 toning of silver papers. 



Platinum gives a very long scale of gradations and renders the delicate tones of the 

 negative better than any other medium. 



There is no gelatin emulsion, therefore the image does not interfere with the 

 spectator's appreciation of the texture of the support. This is a characteristic which is 

 highly esteemed by those artists to whom fine print quality is of importance. 



Platinum is by far the easiest photographic printing process, so far as technique is 

 concerned; it is vastly easier to make a good platinum print than it is to make a 

 bromide enlargement or a gaslight print. 



Disadvantages. — It is rather expensive. At the current prices for chemicals, an 

 8- by 10-in. print costs about 40 cts to make, and an 11 by 14 in. about double that. 

 Against this, however, must be set the fact that the cost of developer is practically nil, 

 the cost of clearing baths very slight, and there is no reason whatever for failures. 

 With a little care, the worker can count on complete success in this work. Of course, 

 to those workers who wish a few fine prints rather than many mediocre ones, this 

 matter of cost has little importance; one good platinum print is more to be desired 

 than a thousand ordinary bromides or chlorobromides. 



Internal modifications of values are not easily made. In this respect Fresson, 

 gum, and bromoil are superior to platinum, for, although it is possible to modify values 

 by brush development of the print with a developer diluted with glycerin, the results 

 are not usually very satisfactory; good prints have been made with this technique, 

 it is true, but in general they are likely to look more like wash drawings than like 

 photographs. 



Platinum is definitely a contact process. Enlargements have been made on 

 platinum paper, but only with very special apparatus, and as a rule it is necessary, if a 

 large print is desired, to make an enlarged negative. This is due to the relative slow- 

 ness of printing, and as a corollary it follows that for contact printing a strong light is 

 required. This involves the use of sunlight, a carbon arc, a mercury-vapor lamp, or a 

 sunlight lamp of the type supplied for therapeutic use. Any one of these is satis- 

 factory; probably the best is the mercury-vapor lamp, and next to it the carbon arc. 

 Sunlight is, of course, the cheapest, as well as the most variable. 



The Negative. — It is commonly said that platinum requires a strong negative, but 

 this is by no means the case; exquisite prints in either high, medium, or low key may 

 be made from soft negatives, and the possibilities of variation are such that excellent 

 results may be obtained from any negative of reasonable quality. It is, however, 

 true that platinum has such a long scale of gradation that to exhaust its possibilities a 

 rather contrasty negative is needed, and it is further true that for average results with 

 an average sensitizer the negative should be somewhat stronger than for average 

 results with a medium grade of chloride paper. Still, practically any quality of print 

 can be obtained from any quality of negative. 



It should be noted, though, that for a given degree of contrast a finer print will be 

 secured from a thin negative than from a dense one, i.e., if we have two negatives of 

 the same contrast, one of them thin and the other dense, the former will give the 



