Toning / metallic toning (French: virage, German: Tonung)


In contrast to tinting, toning is not the simple immersion of a film into a dye bath but involves a chemical reaction converting the silver image. In this reaction the neutral silver image in the emulsion of the positive film is replaced by one consisting of colored metal compounds. These were usually iron ferrocyanide (Prussian Blue) for blue, copper ferrocyanide for red/brown, silver sulfide for sepia or rarely uranium ferrocyanide for reddish brown. Toning had been used in still photography before. But since film was projected on the screen it required translucent toning compounds.

In principle, toned images can be identified easily by the transparent bright image parts and perforation areas, while the shadows and the dark parts are colored in a specific hue (see images on this page). In practice, however, the brighter parts can also be affected by the diffusion of dyeing compounds, or the images were tinted and toned in combination.

There were two chemical recipes available for toning, either a one-bath or a two-bath process. In the one-bath process, the silver image is converted to silver ferrocyanide and then combined with the colored ferrocyanide. In the two-bath process, metallic ferricyanide first bleaches the metal silver to silver ferrocyanide. In the second step, the silver ferrocyanide is converted to colored metal ferrocyanide.

See also mordant or dye toning

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