Cyanowands

[Norberto Rivera]

Anyone want to elaborate on their experience with cyanowands or their vendor-specific equivalents?

We purchased two of them a couple of months ago and I haven't played with mine as much as I should. The few times that I have used it I've noticed that the CA has a tendency to rub off easier than with regular glue. I searched the forums and found some references to "curing" the prints. I just finished fuming three pairs of latex gloves I found in a recovered stolen vehicle. (recovered minus the sound system, go figure that) I used two controls (plastic bag sections) because I also have a new dye stain I'm trying out. Both seemed to be fine as I was unable to rub them off immediately after fuming, but the deposits on the metal clips I used to hold the gloves up inside the chamber I could wipe off rather easily. I guess it's more a result of the surface than it is the glue. Just to be on the safe side I will let the gloves sit until tomorrow. (any excuse to call it quits for the day is good with me hehehe) I am still curious to know what experiences others have had using the wand vs. regular glue.

[mdavis]

My experience with the fuming wands is not exactly positive. The wands (Lightning Powder Co. versions) became difficult, then impossible to light after moderate testing and use. I used them for a short time but found them nearly impossible to use outside with any wind, and very difficult to control over-fuming on most surfaces. I have settled on using them now only for fuming interiors of vehicles through a widow crack.

Fuel is said to be "special" and perhaps using generic butane (Ronson) has clogged the lines. Shouldn't be that touchy.

[Chris Grice]

Many years ago I was told by an employee of Locktite Corp. (which makes cyanoacrylate) that if you heat superglue at very high tempertures that cyanide gas is produced. I don't personally know if this is correct but he advised me to stick with low-heat accelerants like a cup warmer or 60 watt light bulb. I have seen the fuming wands get red hot so have avoided using them. Also, I remember one of the companies that make a fuming wand had a safety recall about 10 years back for some reason or other. I think the convenience of the wands is outweighed by the potential dangers.

[mdavis]

Like so many of the new "innovations" in forensic science, some are failures. The wand is a good idea. It just doesn't work for me. They added fluorescent dye to the cyanoacrylate, but fluorescent materials are not much good unless you can use them in relative darkness. The fumes from the wand are not necessarily heated hot enough to create cyanide because there is no flame as such, just a heated ceramic element that transfers heat to a brass cartridge containing steel wool impregnated with cyanoacrylate ester and the dye. The wands are nearly useless unless you can eliminate drafts or wind which carries the fumes away from the intended surface. With no draft, the fumes rise which means it is difficult to direct them properly to the surface.

If you read the literature, optimal cyanoacrylate fuming is done at about 85 deg. F. and 85% humidity. You cannot control humidity with a wand. The tendency is to over-fume the surface because you can't "see" the latent print until it is over-fumed. If you can see the latent print, you have probably exceeded the optimum amount.

In short, wands have their place in situations where you need fumes in an enclosed area and when you don't have access to electricity.

[Thomas Taylor]

I played around with one of those wands and never got uniform or satisfactory results except in one specific application -- vehicles. To process the inside of a vehicle, I put one "test print" on the inside center of the front windshield. Then I close up the vehicle tight except for leaving one window open just barely enough to stick the tip of the wand inside. I may use two or three or a half dozen or more cartridges to fume the inside of the vehicle, depending on its size and the atmospheric conditions, until the "test print" looks the way I want it. The fuming wands are worth keeping around, if just for vehicles.

[Peter Griffin]

Cyanide gas is formed from polymerized cyanoacrylate (hardened) if heated above 205C or 401F (Safety for the Forensic Identification Specialist by Nancy Masters, page 150).
As for cyanowands, I think they have their place. I find them faster (if processing 1 or 2 items) and easier to control the degree of CA exposure compared to a fume hood (with a bit of practice). I have not noticed a difference in the glue’s adherence, but I cannot really imagine there should be one since they are essentially in the same environment (as fume hood CA), so it should form a ‘spaghetti’ matrix. The vacuum chamber is the only method I know of that effects the CA deposition matrix since it forms small beads, which decreases adhesion to the substrate.
PG

[mdavis]

John O'Lenick is one of the top authorities on cyanoacrylate (CAE) fuming. John is a chemist who gives seminars on CAE work and it is his research that most recent literature is based on regarding humidity, temperature and the formation of CAE on lipid residues. He has done SEM studies on the reaction and formation of CAE on latent print residues. I would suggest reading John's publications for the current thinking on the use of CAE.

I use wands only for providing fuming on the inside of vehicles. Other methods such as temperture/humidity controlled fuming chambers and vacuum chambers are much more in control and provide reliable and reproducable results in a laboratory environment.

[William Pepsis]

Excellent interaction and follow up postings on some of the tendencies of using the accelerated processing method of fuming with Cyanoacrylate-ester. Two (2) additional observations though. The first one Norberto you actually caught yourself. The type of substrate being processed can sometimes be an issue. The second is that it has generally been accepted that the fuming process retards the polymerization of the glue and the fumed item should be left alone for at least 24 hours after fuming to assure hardening. If you were able to rub off the resulting positive developed print and did not wait this could be partially the reason. Our office has had problems with losing positive results on Mylar surfaces even when we do wait 24 hours so I guess more networking and interaction would probably lead to discovering other subject materials not conducive to fuming.

[mdavis]

One of the things that scanning electron microscopes have shown (reference John O'Lenick again) with regard to CAE fuming is that the CAE begins to adhere to lipid residue by forming small threads or fibers, similar to carpet fibers, during the early stages. As the fuming progresses, these fibers begin to mat down and eventually coat over. This is one reason that dusting is often less than satisfactory on over-fumed items. On smooth, non-porous surfaces, it is very easy to over fume because of the tendency to fume until you can see the prints. This can be counter-productive.

The best way I've found to preserve prints fumed on extremely reflective surfaces is to photograph them before you try any processing. If the print is extremely light, dye staining can erode the CAE if stained before it has cured. Dusting may or may not provide detail on very faint residues, and the friction of dusting (magnetic powder is not usually as effective as a fiberglas brush) can also destroy the print.

The substrate is indeed a factor. If highly textured, your best bet is often to "over fume" at high humidity. This causes the CAE to turn white and allows it to be photographed easily, where dusting will tend to fill in the textured substrate and cause background painting and loss of detail.