Forensic Fingerprint Fuming

Introduction

Perform one of the newest fingerprinting techniques currently used by many police departments—Super Glue fuming! In this technique kit, the fumes from ordinary Super Glue are used to “develop” and preserve fingerprints left on a nonporous surface.

Concepts

• Fingerprinting
• Super glue fuming

Materials

Safety Precautions

Sodium hydroxide solution is a hazardous and corrosive liquid; it is dangerous to eyes and can cause skin burns. Avoid contact of sodium hydroxide and Super Glue with eyes and skin. Super Glue fumes may be irritating. Perform this activity in a well ventilated area. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Do not wear cotton gloves when performing this activity—Super Glue generates heat when reacted with cotton. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The leftover sodium hydroxide may neutralized and disposed of down the drain with plenty of excess water according to Flinn Suggested Disposal Method #10. All other materials may be disposed of according to Flinn Suggested Disposal Method #26a.

Prelab Preparation

1. Obtain at least one cotton ball for each fuming chamber and the 0.5 M sodium hydroxide solution.
2. Place the sodium hydroxide solution into a beaker or similar container.
3. Using tongs, dip each cotton ball into the 0.5 M sodium hydroxide solution. Handle the cotton balls carefully—sodium hydroxide is corrosive to eyes and skin. Note: Prepare enough cotton balls for the number of fuming chambers that will be set up.
4. Place the sodium hydroxide–soaked cotton balls aside to dry completely. It is best to allow the cotton balls to dry overnight.

Procedure

1. Obtain a Super Glue fuming chamber and lid, aluminum dish, tube of Super Glue, presoaked cotton ball, a microscope slide, a paper towel and a magnifying glass.
2. Place a moistened paper towel on the bottom of the fuming chamber.
3. Place the aluminum foil dish in one of the corners of the fuming chamber.
4. Place one of the cotton balls presoaked with sodium hydroxide in the aluminum dish.
5. Obtain a microscope slide. Rub a finger against your nose or forehead and make several fingerprint impressions on the glass slide.
6. Place the slide with the fingerprints in the fuming chamber so the surface that contains the latent prints is facing the cotton ball in the chamber.
7. Add three or four drops of Super Glue to the cotton ball and immediately place the lid on the fuming chamber. The cotton ball should begin to emit fumes within a few seconds. Allow the fingerprint development process to continue for 15 minutes.
8. After the development of the fingerprint(s) is complete open the container in a well-ventilated area and remove the slide.
9. Place the slide on a clean, flat surface and examine it with the magnifying lens. The fingerprints will be “fixed” to the slide and prominently displayed as crystalline white traces.

Teacher Tips

• This is a Super Glue fuming techniques kit. It includes enough materials and chemicals needed for 10 complete Super Glue fuming setups. This method may be worked into your current fingerprinting classroom activities or information from the attached Fingerprinting Information Sheets may be given to students to help identify the types of fingerprint patterns and their classification.
• Best results will be obtained if fingers are rubbed against the nose or forehead before placing prints on the slides.
• Fingerprints will begin to develop within minutes using this Super Glue fuming method. However, it is best to allow at least 15 minutes to observe the full development of the prints.
• The development progress of the fingerprints may be checked by quickly lifting the lid and examining the specimen, although this allows fumes to escape. If necessary, add a few more drops of Super Glue to the cotton ball to increase fume output, or replace the original cotton ball with a new one and add a few additional drops of Super Glue.
• If handled and stored properly, the developed fingerprint samples will last for years!
• Other nonporous items may be fingerprinted using Super Glue fuming as well. Large objects that do not fit in the fuming chambers provided in this kit may be placed in large zipper-lock plastic bags or in fish tanks with sealed tops. In fact, items as large as entire cars have been fingerprinted by police departments using Super Glue fuming!
• The aluminum dish provided in the kit is an easy way to contain the Super Glue and prevent it from running off the cotton ball and onto the fuming chamber. Aluminum dishes are also commonly used in the heat generation Super Glue fuming method (see the Discussion section) to provide a wide surface-area platform for the Super Glue to be directly dropped onto.
• Acetone may be used as a solvent to clean up Super Glue spills.

Discussion

Cyanoacrylate is the generic name for glues containing methyl-2-cyanoacrylate. These are typically sold under trademarks like Super Glue and Krazy Glue. Cyanoacrylate adhesives are classified “instant adhesives.”

In most cases, cyanoacrylate is an acrylic resin that rapidly polymerizes in the presence of water to form long, strong chainlike molecules—these are the forces which join the bonded surfaces together. Because the presence of moisture causes the glue to set, exposure to moisture in the air can cause a tube or bottle of glue to become unusable over time. Cyanoacrylate sets quickly, often in less than a minute. A normal bond reaches full strength in two hours and is waterproof.

Super Glue fuming is a process in which items are placed into an airtight chamber and exposed to Super Glue vapors. Common chambers that are used for Super Glue fuming are fish tanks, plastic bags and other specifically designed chambers that are commercially available. When vaporized, Super Glue reacts to the amino acids, fatty acids and moisture in fingerprints. As a result, fingerprint “residue” often turns white and becomes polymerized—or bonded—to the print surface.

In this activity, Super Glue will be placed on an absorbent cotton ball presoaked with sodium hydroxide creating an exothermic reaction. The heat generated from this reaction speeds up fuming and allows the fingerprints to be developed within minutes. This “chemical acceleration Super Glue fuming method” is often is used by police departments for field applications on containers that may have contained drugs, tools found at a crime scene, and beverage containers, such as bottles or cans.

Non-chemical acceleration heat generation is another Super Glue fuming method that is commonly performed. Safe heat sources such as a 60-watt lightbulb placed outside of the fuming chamber or a coffee cup warmer placed inside the fuming chamber may be used to accelerate fuming without using sodium hydroxide and cotton balls. This process generally takes hours instead of minutes. Heat sources to avoid due to safety concerns and because they generate too much heat include soldering irons and hot plates.

Samples may also be fumed using Super Glue in vacuum chamber. The vacuum chamber technique involves removing all of the air from the chamber with a vacuum pump. This reduces the atmospheric pressure and allows the glue to fume in a short amount of time. This technique also allows the Super Glue fumes to penetrate into small crevices. Using a vacuum chamber is perhaps the best technique for many surfaces. As an example, if a plastic bag is fumed in a vacuum chamber, fingerprints may develop even on the inside of the bag.

References

http://www.3dchem.com/moremolecules.asp?ID=325&othername=Superglue (accessed February 2010)

http://absoluteastronomy.com/topics/cyanoacrylate (accessed February 2010)

http://www.detectoprint.com/article.htm (accessed February 2010)