Historically, fingerprint powder has been used to assist latent print examiners, crime scene technicians, and analysts in the detection and collection of latent prints left behind at crime scenes.
In the beginning, powders were often handmade by latent print examiners or police crime scene technicians. Commercially available powders began to hit the market in the s and are now available in a variety of colors and material configurations specifically manufactured for various investigative needs. With so many different color and material configurations, it is important to understand the features and benefits of each type of fingerprint powder.
Color Selection. Black is by far the most commonly used latent print powder color. Black powder is manufactured from a variety of carbon-based powders with a binder added for stability. This carbon-based powder readily adheres to the oily residues generated by contact from fingers and other body parts. Black powders are easy to apply to many surface types, porous and non-porous alike. Because of its versatility, black powder is the workhorse of latent print processing.
Before these powders advanced through further scientific development, there were few other colors available. Black and aluminum were both powders of choice, but black was by far the most popular. Regardless of the surface type or color, black powder was spread and prints were developed.
Examiners would then use a very bright light source to visualize the prints, especially on darker colors that lacked contrast. The developed prints were of exceptional quality; the only problem was that they simply could not be readily seen. White powder works especially well on glass, chromed metals, plastic bags, and dark-colored surfaces. Aluminum powder performs best on glass, plastic, and rubber. Bi-chromatic powder, on the other hand, is typically a combination of black and aluminum powder, although some manufacturers combine the black with a variety of other colors.
The idea behind the creation of the bi-chromatic powder was to assist the examiner with multi-colored surfaces. When processing with bi-chromatic powder, developed latent prints will be seen as black ridges on the light parts of the surface and light ridges on the dark parts of the surface.
Once these prints are lifted, they will always visualize as dark ridges on a white backing card. Material Selection. Powders can be characterized as conventional colorant and base , magnetic colorant and iron shavings , and fluorescent light-stimulated colorant and base. Conventional powders are the most common type of powders used in crime scenes and are typically applied with a fiber or hair brush. They are generally inexpensive, cover a large area when applied with a brush, and readily develop prints on most non-porous surfaces.
The main concern with conventional powders is that they can create a mess. Black powders are generally very light and airy, so the particulate can become airborne at the slightest flick of the brush.
Conventional powders are not designed to work on porous surfaces like paper, but are used in the field none-the-less. Powders may also combine a number of compounds. Dactyl black is made from a combination of graphite, lampblack and gum acacia. Haddonite black is similar to dactyl black but uses powdered acacia instead of gum acaca. Another black powder is called Dragon's blood; it uses the powdered resin of the Daemonorops draco plant.
Additional inorganic materials that are added to fingerprint powders include aluminum dust, fluorescent powders, magnet powders, lycopodium and other metal powders.
Additional items commonly found in fingerprint powder include:. Fingerprint powder is typically gently brushed onto an area, or it is poured onto an area and excess powder is blown away. Magnetic powders use magnetism to keep prints intact; a brush cannot damage any latent prints. Other techniques include using superglue to bind to latent prints and dusting the area afterward to develop a well-defined print.
Michael Carpenter has been writing blogs since He is a mortgage specialist with over 12 years of experience as well as an expert in financing, credit, budgeting and real estate. Michael holds licenses in both real estate and life and health insurance. Fingerprint powder is applied by brushing it onto the surface and works by mechanically adhering to the oil and moisture components of the latent print. When the powder particles adhere to the grease or moisture forming the latent prints, it causes them to become visible.
The developed latent prints are then readily observable and able to be collected, preserved and examined. Sign up for our email newsletter. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Discover World-Changing Science. Christine Craig is a forensic scientist for the Commonwealth of Virginia and specializes in working with impressions.
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