Photographer Jonathan Bailey has written a two-part article on the split toning of prints.
"…split-tones refer to both warm and cold tones simultaneously present in an image. Whereas conventional toning (sepia, for example) will render a print a uniform chocolate brown color, split-toning typically yields shades of reds and blues – occasionally even greens and violets – and therein lies the difference. The effects may range from subtle to extravagant. Generally speaking, split-tones are the result of chemical toners used after normal processing and fixing…"
Part one, Background and Historical Antecedents, is from the from the December 2000/January 2001 Issue of Camera Arts.
Part two, Processes and Procedures, is from the February/March 2001 issue of Camera Arts.