Iodine / Benzoflavone
In developing latent prints with iodine, a long-used method, iodine crystals give off vapors (sublimation) that adsorb physically to the oily substances of a fingerprint.
The brown-colored prints that are developed with iodine are not permanent unless fixed. Benzoflavone fixes and also darkens the print.
The iodine fuming technique can be used on both porous and non-porous surfaces. It works best on fresh prints (usually no more than a few days old).
Iodine fumes are toxic and also strongly corrosive.
Since the iodine fuming technique is in principle non-destructive, other techniques can be used afterwards (e.g., the ninhydrin treatment of paper).
Iodine developed print on envelope
After fixing with benzoflavone, notice the right side of the print
Iodine fuming kit