ABSTRACT
This chapter focuses on Van Dyke brown printing that is related to salt printing, the basis for which was invented in 1842 by Sir John Herschel, mathematician, astronomer, chemist, inventor, botanist, and experimental photographer. It utilizes the transformation of ferric ammonium citrate into the ferrous state, which then could be combined with silver and other metals. In addition, salt prints, calotypes, and Van Dyke brown prints employ silver nitrate as one of their light-sensitive components. A brown print can be made on paper, leather, or fabric and can yield permanent images rich in detail with subtle separations in the middle tones and shadow, ranging from pale to deep Van Dyke brown. A photographic negative, when placed in contact with the silver-based emulsion, produces a positive picture after relatively short exposure to daylight or ultraviolet light. The longer the exposure, the darker the tone of the print.
