Cyanoacrylate or Superglue fuming is a common practice in crime labs and crime scenes.
Cyanoacrylate adhesive, better known as superglue, was first discovered by Harry Wesley Coover Jr., who was experimenting with acrylates for use in clear plastic gun-sights during World War II. He gave up because they stuck to everything they touched.
In 1951, Eastman Kodak researcher, Fred Joyner, who was working with Dr. Coover at Eastman Kodak’s laboratory in Tennessee, was testing hundreds of compounds looking for a temperature-resistant coating for jet cockpits. When Mr. Joyner spread the 910th compound on the list between two lenses on a refractometer to take a reading on the velocity of light through it, he discovered he could not separate the lenses. His initial reaction was panic at the loss of the expensive lab equipment. He ruined the machine.
In 1958, Dr. Coover saw an enormous opportunity, which led to the first incarnation of Super Glue, called Eastman 910, hit the market.
Super Glue gained fame for its incredible tenacity, but nearly 20 years passed before this product found its way into the field of forensic science. Scientists in Tokyo’s National Crime Laboratory discovered that white fingerprints kept appearing on bottles of Cyanoacrylate they kept in their lab. They subsequently discovered that white fingerprints could be developed on most non-porous surfaces, simply by exposing the invisible undeveloped latent prints to superglue fumes.
Today, cyanoacrylate fuming enjoys widespread use in the crime lab and crime scenes all over the world.
So what is going on here? Simply this: when CA fumes come into contact with moisture (about 90% of what a latent print is composed of) it polymerizes. Polymerization is a process during which relatively small molecules (monomers) combine chemically to produce a very large, chain-like molecule—known as a polymer. Many thousands of monomer units are incorporated in a single molecule of a polymer.
In the case of latent print development, the CA fumes polymerize with the moisture of the latent print residue to form a rock-hard polymer that defies removal.
In today’s world of criminalistics, the advantages of using CA fuming are obvious: Fragile latent print ridges become virtually impervious to physical damage or destruction. Of course, the resulting prints are white but this isn’t a problem. They can be colored using regular latent print powders without fear of brushing them print away. Certain liquid dyes may be applied too, allowing for excellent photographic contrast.
Over the years, and in a sense of urgency, various methods have been employed to accelerate CA development. Merely exposing a surface to the fumes may take 8 hours or more for the results to be seen. A variety of concoctions were tried as accelerators. Treating cotton pads with sodium hydroxide was popular until the safety issues compelled many users to find other means of speeding up development.
Today, the most popular, and the safest methods used include applying heat to the CA liquid or simply squirt some CA onto a 100% untreated cotton pad. Heat is a little bit faster than the pad concept.
While CA fumes are non-toxic, they are noxious, so latent development is best performed inside an enclosure. This approach also contains the fumes in an area where they will do the most good. Pictured below are two such developing chambers: one is portable for crime scene use, and it uses disposable plastic bags for the chamber. Heat may be applied to the glue using a small coffee warmer. The other apparatus is a glass enclosure with built in heaters.
Development is usually finished in 15 to 20 minutes in either of these approaches to development. Or if time isn’t critical, cotton pads work well with the results available in less than an hour.
Virtually any latent print powder can be used to apply a contrasting color to developed latent prints. Liquid dyes such as Ardrox, Basic Yellow or Rhodamine 6G are popular and each of these provide visible latents as well as fluorescent prints.
The advantage of using latent powders is that once the latents are photographed, they may be lifted using tapes or other special lifting devices.
Learn more about different latent processing methods by downloading the booklet: Overview of Latent Print Development Techniques.
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