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Prints development
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Prints development
Prints development
Hard, nonabsorbant surfaces require the application of powders to bring out the latent print.  Powders come in a variety of colors but all are made of volcanic ash.  Colors are chosen to contrast with the background surface so white or yellow may be used on black and red may be used on white for example.  Powders may also have a magnetic base added to the ash to control the mess created by dusting for prints.  Magnetic powders work best on burglary scenes to help minimize the mess for the victim.  Magnetic powders are also used to help develop prints found on human skin.

Porous surfaces are developed using chemicals that react to components in the print.  For instance, fatty oils and condensation respond to iodine.  Salt from perspiration (sweat) respond better to silver nitrate.  Ninhydrin is used when amino acids are present.

Nonporous surfaces like metal and plastic and porous surfaces like paper and skin respond best to cyanoacrylate fuming.  Cyanoacrylate fuming is also called superglue fuming.  This process was discovered accidentally in a lab when superglue spilt.  The fumes revealed fingerprints on the keyboard the scientist was using.  The process has been refined to the point where you can do this lab at home.  I will tell you how soon.

All prints are documented by photographs.  Some prints can only be documented on film because they flouresce under UV or alternate light sources.  Many are also preserved on lift tape and kept on file on computer databases.  Prints can last for years under good conditions and have been found on old crime scenes.