Posts Tagged ‘print development technique’
It is generally thought that the chemical latent print development technique first used by law enforcement is angry Iodine. This process is used on porous surfaces such as paper, cardboard and wood raw like most other chemical processes. Iodine fumes react to the sebaceous (oily) secretion is often left by contact with fingers and palms. Iodine works best when the mold is considered fresh as robbery or demand a ransom note. Iodine crystals soften at room temperature and above (70-degrees F, 21.111-degrees C). Sublimation is the process where a solid changes directly into a gas. Object to be “muttered Iodine” exposed crystals and orange to brown latent fingerprints appear. Mold is a “fugitive” in that they start to fade after a few minutes of development, so they must be photographed or chemical fixatives should be applied. Fuming is best done in a room or even a plastic bag Zip Top.
Ninhydrin (2,2-Dihydroxyindane-1 ,3-dione) / DFO (1,8-Diazafluorene-9-one)
Ninhydrin was first developed for use in research laboratories to detect proteins over a century ago. Law enforcement became interested in it when it was determined the chemical that produces the purple color in the presence of amino acids (the constituents of human sweat). To use, Ninhydrin dissolved in a solvent and then applied to porous surfaces. Normal development may take 24 hours or more, but the acceleration can be achieved by the application of heat-especially in the form of steam from a steam iron. With the application of steam, latent prints appear within minutes. DFO is (a synthetic variation) Ninhydrin analog, and while it works the same way, he also produced fluorescence under ultraviolet light.