DOUBLE TONING.

Several of the early publications mention double toning as a partial toning with a metal tone followed by a second tone in either another metal tone bath or a dye mordant tone. One method recommended by Eastman Kodak [1922] was to partially Blue tone to Prussian blue and after a few minutes to remove the film, wash briefly, and immerse in Safranin dye solution. The result would be a blue tone in the shadows and mid-tones and pink highlight tones. This could be the very common blue/pink effect seen frequently in European films of this period, although most effects of this sort were the double effects below.