Superglue Fuming Doorknobs
Written by Mark Kollar   

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SUPERGLUE (cyanoacrylate) fuming is a simple, economical and common method used by the forensic services in order to develop and preserve fingerprint evidence. This relatively safe process assists in quickly visualizing latent fingerprints on a wide variety of surfaces and hardens to secure the fingerprint in place. This process allows for multiple enhancement and lifting techniques, as well as stabilizing the print for transportation from the crime scene to the laboratory with minimal risk of destroying the print.

The process does, however, require an airtight chamber to contain the fumes, thereby making the procedure extremely challenging for some commonly encountered evidentiary items such as doorknobs. The technique presented in this article solves the problem of containment for doorknobs, simplifies the process by utilizing a non-electrical source of fume production, and uses inexpensive, readily-available materials.


Prior to superglue fuming an item, there are several considerations to ensure the safety of the investigator and to minimize as much as possible the risk of property damage.

When dealing with any chemical procedure—and in accordance with sound crime-scene management guidelines—personal protective equipment should be worn when dealing with the superglue fuming process. Powder-free latex or nitrile gloves and eye protection are recommended and inhalation of the fumes must always be avoided.

An additional consideration is the potential damage this process may cause to some surfaces. In general, the white, hardened superglue residue can be removed using acetone (nail-polish remover) or mineral spirits (paint thinner). However, these solvents themselves can be damaging to some surfaces.

Also, the possibility exists that the fumes could propagate internally into the lock and clog the mechanism. Although this scenario is unlikely, informed consent should be obtained from the owner or a search warrant should be employed prior to attempting this technique.

Materials and Equipment Needed

Cotton balls
Baking soda (sodium bicarbonate)
Distilled water
Pre-mixed superglue
Gallon freezer bags (clear)
Typical fingerprinting supplies (i.e. fingerprint powder, brush, lifting tape and backing material)


Some basic preparation of the supplies is required prior to response to the crime scene. Although the hands-on portion of the preparation only takes minutes, up to 24 hours of drying time is necessary. Upon completion of the preparation, it is highly recommended that one tests the materials on a non-evidentiary doorknob both to verify the effectiveness of the supplies and for practice and experience.

The first step is to place a quantity of distilled water into a cup or beaker. The amount can vary depending on the batch size you desire to make, but don’t fill the container more than halfway full to avoid overflow during subsequent steps. Filling a large 12-ounce cup with 150 mL of distilled water works well.

Next, the water must be saturated to its maximum capacity with baking soda. This is simply done by slowly adding baking soda to the water while stirring until no further baking soda can be dissolved. (You will know when you have reached that point when excess powder begins falling to the bottom of the glass.) Depending on the temperature of the water and other variables, the amount necessary can vary from 50-75 grams per 150 mL of distilled water. Exact measurements are not critical, but it is better to err on the side of too much baking soda than not enough.

Finally, cotton balls are individually submerged into this solution for approximately five seconds each and allowed to completely air dry, usually overnight (see Figure 1).

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.
Fuming the Doorknob:
Print Development
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).

Figure 2: Plastic bag is taped over the doorknob to provide a fuming chamber. Note the presence of a test print. Note also that flaps have been cut around the mouth of the bag to aid in the taping procedure.
The reaction between the superglue and cotton ball, expedited by the dried baking soda, begins producing fumes almost immediately. Although the fumes themselves may not be visible, the effects they have on any latent prints will be obvious within several minutes. Depending upon various factors, such as ambient temperature, the time necessary for the fuming process can range from five to 15 minutes. Allowing the doorknob to fume for too long will result in the ridge detail and minutia of the print becoming obscured. Therefore, it is crucial to monitor the test print and begin venting the bag once the test print shows signs of whitening.
Vent the bag by removing the tape from the top and allowing the fumes to dissipate for several minutes. Be certain not to place your face near the bag while venting, as the fumes will cause eye and lung irritation. After the majority of the fumes have dispersed, the bag can carefully be removed and discarded.
Print Enhancement
and Collection
Now that any fingerprints are visible and fixed by the superglue-fuming process (see Figure 3), there are several options available for enhancement and collection. Individual preferences, the severity of the crime being investigated, and the availability of equipment are all factors in determining the best method to utilize.

Figure 3: Fumed print on object’s surface.
If the nature of the crime warrants, the preferred method is to remove the doorknob and submit it to the lab after fuming. Although any prints should be relatively secure, excessive handling or rubbing should be avoided. With the actual doorknob in hand, the lab can use an assortment of different dye-stains, such as MRM-10, that react with the superglue to fluoresce under an alternate light source (see Figure 4).

Figure 4: Fumed print with MRM-10 dye stain illuminated by an alternate light source (445 nanometers) under lab conditions.
If attempts are to be made at lifting the fingerprint in the field, photography should always occur first. Macro, medium range, and overall photographs—both with and without a reference scale—should all be taken, with emphasis on the macro. Be certain to follow your agency’s standard operating procedures for evidence photography, as the laboratory may eventually want to analyze the images as evidence.
Once the photography is complete, the prints may be enhanced with black volcanic fingerprint powder. Clear lifting tape can then be used to lift and transfer the print to a clear acetate sheet or other backing material (see Figure 5). As the print is fixed in superglue, it is often possible to take multiple lifts of the same print, while applying additional applications of fingerprint powder between lifts, as necessary. Multiple lifts should be denoted as such.

Figure 5: Fumed and powdered print was lifted with tape and secured to a transparent acetate.
Tight, difficult-to-reach places are commonplace on doorknobs, but may contain some of the best evidence. In areas where tape lifts are not practical, silicone-based casting materials such as AccuTrans or Mikrosil may be used. Be sure to use a color that contrasts with the color of powder you are using (see Figure 6).

Figure 6: Fumed and powdered print that was lifted with white AccuTrans.
Superglue fuming of doorknobs may provide an investigator with the highest probability of recovering identifiable latent fingerprints with minimal effort, time, and expense for the investigating agency.
Once a print has been developed by the fuming process, numerous options are available for enhancement and collection. When conducted properly, the process also reduces the risk of inadvertently destroying important fingerprint evidence.
Although this discussion was limited to doorknobs, the procedure is valid and can be applied to other objects and surfaces as well. Practice and experimentation on non-evidentiary items will hone the investigator’s ability to obtain fingerprint evidence on actual crime scenes.
About the Author
Mark Kollar is a special agent in the Crime Scene Unit of the Ohio Bureau of Criminal Identification and Investigation, a division of the Ohio Attorney General’s Office. He can be reached by phone at this number: 330-659-4600, ext. 347 Or by e-mail at the following: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

"Superglue Fuming Doorknobs," written by Mark Kollar
May-June 2010 (Volume 8, Number 3)
Evidence Technology Magazine
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