Very little information is available on this very rare process. Instead of immersion into a dye-bath the positive print was coated uniformly with a varnish. This technique can be identified by the lack on dyes in the perforation area and by the ...

For tinting, the positive print is immersed into a variety of dye baths, scene by scene. To this end, the print has to be cut into the corresponding fragments and reassembled after the dyeing process. The dye homogeneously attaches over the entire image’s gelatin including the perforation area. Usually synthetic dyes were dissolved in a weak acid solution to form a chemical bond with the gelatin.

Kodak Sonochrome was a specially prepared tinted film for sound film that did not interfere with the spectral sensitivity of the photo-electric cell for the reading of the optical sound track. The 17 Sonochrome tints were dyed in mainly light hues ...