How does cyanoacrylate fuming work

Explain how invisible latent fingerprints are developed and analyzed through chemical means. Per Demo: a drinking glass or other smooth, non-porous object warm water shallow paper cup superglue aluminum foil heat lamp heat bulbs available at hardware or pet stores large, sealable plastic bag pie tray. What is the advantage of fingerprint fuming over dusting for fingerprints?

Teacher Tip: Monitor the evidence. If left for too long, the fingerprints will overdevelop and the spaces between the ridges will fill in, obscuring the pattern. Details Activity Length 20 mins. Arches have lines that start on one side and rise and exit on the other side of the print. They look like a hill. Loops have lines that enter and exit on the same side of the print. They look like an upside-down U. Whorls have circles that spiral and do not exit on either side of the print.

Objectives Explain how invisible latent fingerprints are developed and analyzed through chemical means. Expand All Collapse All. Page Content. Spanish Hmong Somali. Forensic Testing Services. Drug Chemistry. Questioned Documents. Latent Prints. Finger ridges contain a large number of sweat pores. When the finger touches any surface, the sweat from these pores get deposited in the form of contours which are the mirror image of the ridge patterns.

Since sweat is colorless in nature, its deposition on a surface also produces colorless impressions and these impressions are called latent fingerprints. Forensic scientists in the Tokyo National Crime Lab discovered that the fumes from cyanoacrylate adhesives CA or superglue, reacted with the moisture of latent fingerprints in such a way that a latent print on a non-porous surface was covered with a hard coating that encased the delicate ridge structure of the latent print.

The ridge detail of the fingerprints on non-porous surfaces such as plastic, glass and finished and unfinished woods can be exposed to cyanoacrylate fumes. Materials and Equipment Needed Cotton balls Baking soda sodium bicarbonate Distilled water Pre-mixed superglue Gallon freezer bags clear Tape Typical fingerprinting supplies i.

Figure 1: Application of sodium bicarbonate solution to cotton balls. After drying, the prepared cotton balls may need to be rolled or lightly crushed in order to break up any excessive baking-soda residue on the exterior of the ball. Once completely dry, the balls may be stored together in a paper bag until needed. Although not specifically studied, the shelf life is expected to be a minimum of several years.

The actual procedure to superglue fume a doorknob is quite simple and relatively quick. First, the area around the doorknob needs to be examined for any evidence that could potentially be disturbed by the forthcoming process. Generally, this can be done with a visual observation with oblique lighting, although an alternate light source can also be utilized depending on the type of evidence you expect to find.

If the door itself is to be fingerprinted, it should be done before the doorknob is fumed. Once the area around the knob has been cleared of evidence, a gallon or larger freezer-type bag is placed over the doorknob, centering the knob within the bag.

Be careful not to touch the doorknob with the bag as it could smear any latent fingerprints. Freezer bags are constructed of a thicker plastic and are therefore stiffer, making this task far easier. Further, freezer bags are usually transparent, allowing for the progress of the reaction to be monitored. The bottom half of the bag is then taped to the door, leaving the top half open to allow access to the bag.

Placing one-inch slits around the zippered mouth of the bag creates flaps that can be taped to the door. Before the fuming begins, a test print must be placed inside the freezer bag to serve as a control. This allows the progress of the fuming process to be gauged to indicate when the procedure is finished.

Using an ungloved finger, wipe an oily area of your face, such as your forehead or along the sides of your nose. Next, reach that finger inside the freezer bag and place a fingerprint four to five inches inside the opening, on the bag.

On the exterior of the bag, use a marker or pen to draw a circle around the area where you left the test print. This will serve as a reference to help you find your test print. Next, place five to six drops of superglue on the surface of one of the prepared cotton balls. Working quickly, carefully add the cotton ball to the freezer bag through the unsecured top.

Be certain to prevent the ball from coming into contact with the doorknob, and be careful not to drip any superglue on the doorknob.

Finally, tape the top of the bag to the door to create an airtight fuming chamber around the doorknob see Figure 2.