By Pat A. Wertheim
Some latent print technicians believe superglue should be listed second only to powder as the most effective latent print development technique. Others believe it should come first. Either way, no one can deny that superglue fuming is the most revolutionary new method to be discovered since the invention of powder. Superglue fuming works on many surfaces where powder is ineffective, such as plastics, and has the advantage of fixing the print on the surface for later presentation in court.
First, you need a more or less airtight container to hold the evidence. Three elements are necessary inside the chamber: superglue fumes, humidity and warmth. For a chamber, I regularly use a large coffee can for small items such as a handgun or a baggie of dope. An aquarium is an ideal medium-size chamber. For a large chamber, an old refrigerator body with removable wire shelves is excellent. I have also used cardboard boxes (with the seams taped) and plastic garbage bags (blown up loosely like a balloon, then closed with a wire twist).
For humidity inside the chamber, you first need to analyze the humidity outside the chamber and the temperature of the surroundings. If you are in a warm location with high humidity, you probably do not need to add any moisture to the chamber in order to get good results. If the humidity in your area is low or the temperature is cold, a glass of hot tap water works well in a small chamber, while a tray (such as a photo developing tray) of hot tap water works well in a large chamber. In a coffee can, a long huff of breath adds plenty of moisture. Be careful not to put very cold evidence into a warm, humid chamber, as condensation may damage latent prints. Allow cold evidence to warm up before placing it into a chamber.
For warmth, again analyze your surroundings. In a warm climate, perhaps no warming device is necessary for the chamber. The best results seem to occur at about 100 degrees Fahrenheit with 80% humidity. In a large chamber, such as an old refrigerator body, one or two 200-watt light bulbs will raise the temperature to a good range, even on a cold day. Cheap ceramic light fixtures mounted into the floor of the refrigerator are perfect. Run the electrical cord out the door, and the rubber gasket will seal around the cord when you close the door. Then you can simply plug the cord in to turn on the lights.
Introducing the superglue fumes into the chamber is the last step. Some technicians prefer the glue packets which peel apart like Polaroid film. Some prefer plain liquid glue. In the coffee can, drip 10 or 12 drops around the side of the can near the top. Place the evidence in the can, being careful not to allow it to become glued to the can. Finally, huff some breath into the can as you gently snap the lid down. Five or ten minutes should be sufficient time. In a 5 gallon aquarium, I would use 10 to 12 drops of glue in a small aluminum dish, either on a hot plate or floating in hot water (do not allow water to get into the glue, or vice versa, as that will restrict the fuming action). In a larger chamber, calculate the amount of glue at the rate of one-ounce (28 g) per 100 cubic feet of container volume. Again, a hot plate helps evaporate the glue. If you are using light bulbs mounted on the floor to heat the chamber, you can construct a grill immediately above the top of the light bulb, even in contact with it, and place the small pan of glue directly over the light bulb to evaporate the glue. In containers larger than the coffee can, I generally use about 30 minutes fuming time.
The Home Office at Scotland Yard rates superglue fumes as nontoxic, but irritating. The fumes should be vented away from you, or the container should be placed in a fume hood or other location that allows good ventilation, such as an outdoor shed or carport. Some people are able to open the chamber within the office and it doesn’t bother them. This is not the best recommended method. Please read the MSDS for the properties of superglue. If you accidentally glue skin to skin, or get superglue in your eyes, get immediate medical attention.
The best way to learn how to use glue effectively is to experiment. It is a simple, dependable process. It even makes a great science fair project for student in school. For the cost of a tube of superglue from the grocery store, and an old coffee can, your elementary or junior-high age children can construct a fantastic science experiment which will be a guaranteed attention-getter at the school science fair. You can achieve even more impressive results in the lab with a little effort and practice.