Ask A Scientist Chemistry Archive

name         Susan
status       teacher
grade        other
location     OH

Question -   I am a Science Education Masters Student and 25 year
experienced health care professional.  I am preparing a demonstration for
my science methods class.  I plan to demonstrate using super glue to fume
finger prints.  I found much information about the procedure, but
information on the chemistry behind the reaction is vague.  Could you
help me with finding the chemical reaction that takes place between the
super glue fumes and the finger print?
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Cyanoacrylate monomers polymerize rapidly in the presence of water, and
other functional groups such as amines, amides, hydroxyl, and carboxylic
acids. All of which are found in the oils that are left by fingerprints.
The vapors of the various cyanoacrylates polymerize to form a "sticky"
polymer that forms a latent image of the fingerprint. This is "developed"
by dusting the fingerprint with an appropriate powder that sticks to the
sticky cyanoacrylate latent image. This "developed" image can then be
photographed or otherwise scanned to image the print. The following sites
describe the chemistry to some degree:

http://www.xs4all.nl/~dacty/cyanoacr.htm

and 

http://www.cheresources.com/criminalszz.shtml

Vince Calder
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