PHOTOGRAPHIC MATERIALS 145 



The exposure scales for the three contrast grades of a typical enlarging paper are: 

 normal, 32; medium, 16; and contrast, 11. The scales for the various contrast grades 

 of a typical amateur contact-printing paper run from 45 for the softest to 4.5 for the 

 most contrasty. 



Image Tone {Color). — The chloride emulsions and the bromide emulsions usually 

 tend to give images of neutral or cold black tones on normal development, and many 

 of them will give definitely blue-black tones with very active developers. Slightly 

 warm tones can sometimes be obtained with restrained or slow-acting developers, 

 but the possibilities for control are normally rather limited. 



The fine-grain chlorobromide emulsions tend to give warm-toned images on direct 

 development, particularly with the slower types of papers. Even warmer tones, 

 ranging to definite browns, can be obtained by the use of restrained developers. 



Also, the colors given by the various aftertreatments depend very markedly on 

 the size and condition of the grains in the original silver image. The effectiveness of 

 the treatments also depend on the condition of the silver grains. Thus the direct 

 sepia-toning solutions, such as the hypo-alum toner, work comparatively rapidly and 

 give pleasing results with the naturally warm-toned images on chlorobromide papers, 

 but work only very slowly, if at all, with the coarse-grained cold-tone images on 

 bromide paper. On the other hand, the bleach and redevelop type of sepia toner 

 which works satisfactorily with cold-tone images tends to give unpleasant yellow 

 tones with the naturally warm-tone images. 



In addition to the inherent color determined by the size and condition of the grains 

 of the silver grains, the apparent-image tone is markedly affected by the color of the 

 base, which is usuallj^ white or very slightly tinted cream or buff but is occasionally 

 supplied with a comparatively strong color. 



Sheen. — As has been mentioned, paper surfaces vary in sheen, or the ratio between 

 specular and diffuse reflection, from the almost purely specular glossy surfaces to the 

 almost purely diffuse matte. Although the degree of gloss probably could be expressed 

 quantitatively, as by the percentage of specular reflection, this would be of little value 

 to most users, and the descriptive terms such as glossy, luster, semimatte, matte, etc., 

 are more generally understandable and useful. 



While the choice of sheen is largely a matter of personal preference, some types of 

 prints definitely call for specific surfaces. Thus small contact prints are generally 

 made on glossy papers because of the greater density range and the sharper rendering 

 of fine detail. For the same reasons the glossy surface is preferred, usually demanded, 

 for pictures to be reproduced by any of the photomechanical processes. For portrait 

 and pictorial prints on the other hand, the softer and less glaring surfaces, such as 

 luster and semimatte, are usually preferred. The matte surfaces are easiest to work 

 on with pencil or water or oil colors. 



The sheen is controlled by incorporating in the emulsion various inert substances 

 such as starch and by varying the composition and method of application of the 

 baryta layer. 



Texture. — In addition to the almost microscopic surface irregularities which con- 

 trol the sheen, the papers may have coarse irregularities giving various degrees of 

 roughness to the surface. Smooth surfaces can be obtained with any sheen from 

 glossy to absolute matte, but the rough surfaces cannot give a real gloss. 



In addition to the various degrees of roughness, some special-purpose or novelt,v 

 papers have a definite surface pattern such as the linen finish. 



Smooth or fine-grain surfaces are preferable for small prints, while the rougher 

 surfaces may be valuable for large prints and enlargements, either for suppressing an 

 excess of fine detail or, with a high degree of enlargement, for concealing lack of fine 

 detail and suppressing the apparent graininess. 



