The Sticky Side of Life

Given, the importance of developing latent prints on the sticky-side of tape, several methods for revealing them. Much like the “dusting” method of latent print revelation, a series of sticky-side wet powders are available. Generally, these are dry powders which are suspended in an aqueous solution with an anionic surfactant. Very likely the forces to adhere the grains of powder to the fingerprint reside are non-covalent interactions. However, it is not clear what role the detergent plays. The surfactant may simply act as a wetting agent ant allow the powder to spread out over the surface of the tape. On the other hand, the surfactant may also facilitate the interaction between the powder and the oily fingerprint residue. A recent article in “Science and Justice” determined that the powder materials are generally titanium dioxide based with traces of aluminum and silicon. A popular surfactant solution used in commercial sticky side powders is called “Photo-Flo 200” which is an aqueous solution of propylene glycol and p-tert-octylphenoxy polyethoxyethyl alcohol (octoxynol 9). An article in the Southern California Association of Fingerprint Officers suggests that a regular fingerprint powder can be suspended a dish detergent solution to create a home-made sticky side powder. In my experience this is a quite dramatic experiment. You brush this black goo on the tape, wash it off, and presto – a nice print!

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