This consists of first converting the silver image into silver
ferrocyanide by a suitable bleaching bath, thoroughly washing, and
acting upon the ferrocyanide image with a metallic salt, usually in
presence of an acid, the metallic ferrocyanide being produced by
double decomposition. The reaction, however, is never complete, so
that the image is mixed with undecomposed silver ferrocyanide which
tends to make the image opaque, but at the same time it also adds
“body” to the latter. Providing allowance is made in the original
positive for this intensification, good tones are obtained. (See Tone
G.)