Advances in Fingerprint Technology.pdf

carbon graphite. The best “fixer” was a proprietary silicone-based, watersoluble
coating named SP-F (Taiho Kogyo Co. Ltd.). Frank and Almog 35
tested particles other than MoS 2 in suspension, including barium sulfate,
titanium dioxide, talc, zinc oxide, zinc carbonate, and basic zinc carbonate
to look for a suitable lighter colored entity to interact with the fingerprint
residue. Best results were seen with 0.66 g zinc carbonate, 20 mL water, 0.06
g Tergitol 7, and 55 g dimethyl ether. They further noted that particles of
2-µm average size adhered better than those of 6-µm average size. Springer
and Bergman 36 have described the preparation of SPR containing the fluorescent
dyes Rhodamine 6G and Brilliant Yellow 40 (BY40). The basis for
using these dyes is more fully developed below under post-treatment of
cyanoacrylate latent prints. The preparations all worked initially, but the R6G
reagent had poor shelf life. A BY40 suspension of 100 mL of 0.1% BY40 in
ethanol mixed with 100 mL stock SPR showed consistently good results.
Chemical Fuming and Enhancement
Iodine Fuming
The iodine fuming technique has been used for latent print development for
at least a century. Several variations of the fuming procedure have been
proposed over the years. 1,37-39 The mechanism of the iodine fuming reaction
was initially thought to involve the reversible addition of iodine to the double
bonds of the unsaturated fatty acids in fingerprint residue by the process of
halogenation. More recent research by Almog, Sasson, and Anah 40 suggests
that the mechanism of interaction involves physical absorption rather than
a chemical reaction. When iodine crystals are warmed, they produce a violet
iodine vapor by sublimation. The iodine fumes are absorbed by the fingerprint
secretion residues to give yellowish brown latent prints. The iodine
color is not stable, however, and is short-lived unless the iodine is chemically
fixed (see below). There are four ways to develop latent prints with iodine.
Iodine Fuming Gun Method
An iodine fuming gun can be made from either a glass or hard plastic tube.
Fresh calcium chloride crystals should be used as a drying agent.
1. Place 0.5 g iodine crystals into the fuming gun.
2. To fume a surface containing latent prints, the nozzle of the fuming
gun is moved slowly over the surface at close range, approximately
0.5 in. away.
3. Blow air into the mouthpiece of the fuming gun (the end containing
the calcium chloride crystals) through a connecting tube.