Iodine Fuming
Iodine fumes react with oils and fatty deposits to produce a temporary yellow-brown reaction product. Iodine is useful on fresh prints on porous and non-porous, non-metallic surfaces. Do not use iodine to fume metal surfaces as it is highly corrosive to metal—even stainless steel.
Developed prints must be fixed or photographed immediately because reaction will rapidly fade. Use iodine before ninhydrin and silver nitrate.