Rhodamine 6G, history and how and wherefrom?

[antonroland]

I have been surfing the web a lot on R6G lately and found a huge lot of info from mixes, chemical compositions and even Nd:YAG dye lasers but I would like to hear from anyone who knows who could tell me more about how R6G came about to be used in the current forensic environment?

Much appreciated,

Cheers

[David L. Grieve]

I was informed about Rhodamine 6G from the old master, E. Roland Menzel, back when he was doing research in Canada during the early 80s. Since Roland had done his initial exploration in laser copiers with an argon-ion, the choice was not a particular flash of genius. for the absorption and emission curves of Rhodamine 6G are ideal for argon-ion. There was some concern the dye was a carcinogen that prompted a search for something else, but nothing was quite as effective. Eventually Rhodamine 6G was demonstrated by Nancy Masters to be safe unless ingested in large quantities.

As Roland was fond of saying, he was a physicist, not a chemist, and is infamous for making a mess of the FBI's brand new forensic wing at the Academy. I was in the class when he dumped an unknown quality of the dye in a beaker of ethanol, then spun the contents around to mix. Liquid went flying everywhere inside the fume hood, confirmed later when he fired up the laser. What a glow!

[Ernie Hamm]

In line with Dave's posting, E.R. Menzel published "Laser Detection of Latent Fingerprints on Skin", Journal of Forensic Sciences 27:4 (1982). This is the earliest reference I know to the use of R6G.

[David L. Grieve]

Thanks for the reminder, Ernie. I believe that was co-authored with Duff and Dalrymple. Brian probably has his own list of stories working with Menzel. But this is another example of fingerprint detection by accident.

[antonroland]

Will order his book then.

Thanks for the inputs folks...what I really would like to know and hope to find in the book is how Rhodamine came to be used as a dye for CA treated latents to start off with.

Have a great weekend!

[David L. Grieve]

There is not much of mystery as to the selection of Rhodamine 6G. Available at the time was a booklet put out by Kodak of dyes their chemical division manufactured that published the absorption curves of the dyes along with their emissions curves. Hard for us to realize now but Kodak was a major supplier of dyes at the time, especially those with potential for luminescence. What that showed was the wavelengths of excitation for each dye and the Stokes shift for the emission. Since Menzel was familiar with the argon-ion laser, he eliminated those dyes that were not excited by the strongest lines of the argon-ion, and checked to make sure the emission was beyond the narrow band filter of the goggles. Rhodamine 6G was ideally suited for this.

As other lasers were utilized, Rhodamine 6G remained effective. The versatility of this dye is the large excitation curve, which includes lines from many lasers and the utility that its emission is above the normal cutoff of 630-660 nm. Both argon-ion and Nd:YAG lasers would excite the dye and luminescence could be readily observed through orange goggles. Roland was a good physicist and could use references well. And by then he was at Texas Tech with an endless supply of grad students to do the heavy lifting.

[David L. Grieve]

I'm sorry, but in rereading your question, I realized I did not answer it all.

At the time Roland was pursuing dyes for the argon-ion laser, CA was not that well known or used. Paul Norkus and Ed German had reported on the procedure learned from the Japanese about this time, and the Canadians had been given instruction on the use of the adhesive but then told an application for patent had been made and any use could be a violation. The British studied CA about this time but determined the procedure was less effective than vacuum metal deposition. To be fair, the test was only on soft plastics in which vacuum metal excelled.

I had learned about CA and had passed that on to Roland, but the procedure at the time was not accelerated. At room temperature and without regard to humidity, CA processing might take two or three days to complete. Roland pursued his interest in Rhodamine 6G using treated magnetic powder but that was not very effective. When Frank Kendall discovered how to accelerate the CA process, this not only enabled a reasonable processing cycle of non-porous items, but provided a means for Roland to experiment with CA developed impressions. He was the first to inform me that Rhodamine 6G dissolved in ethanol was readily absorbed by the polymer. In short, he had settled on the dye of choice and now had the means of best delivery. Of course he did not have many specifics and urged using a "matchhead" of Rhodamine 6G for 100 ml.

Roland's book is excellent but contains no references or meaningful footnotes. That is not surprising to me, for Roland was not fond of sharing credit. I loved the man dearly but his priorities were Roland first, then science. To fully explain that, he and I became contestants in a tequila shooting contest at a conference. Several others started the dare but Roland and I ended up the last two standing. We were tied when I just could not drink another shot. Roland stood up, held the glass high and said, "Moderation is not a Germanic virtue." He down the shot, fell over backwards and passed out.

[antonroland]

David

Thank you very much for those very informative responses. Mr Menzel sounds very much like a previous commanding officer I was privileged to work under. He was a master in the B&W darkroom but cleaning up after him was a nightmare

He also had a system of very precise measurements...one medium pour of this...expose it for as long as you count to 5....

I suppose these and other bits of info I'm after are rather trivial in the grand scheme of things but I really enjoy collecting (less useful to some?) bits of information as I am never satisfied until the whole background info puzzle has been built to my satisfaction.

I think I will order his book anyway since my latest mission in life is to know the origin and mainstream applications of all we use in latent print detection and photography.

I just have to hope that some more folks who think like me will see this and other future threads.

Thanks again,

Anton

[David L. Grieve]

Anton,

I think your desire to understand origins is admirable, not a waste of time. When instructing, I always included the how and why of a procedure or technique whether they were flashes of brilliance, simple trial and error or, in many instances, the result of pure coincidental luck. Luck could hasten the adoption or delay it, depending upon good or bad luck.

For instances, Frank Kendall discovered that a cyanoacrylate ester adhesive was manufactured by Kodak in the 1960s but did not do well. Kodak marketed the product to photographers primarily as an instant repair, something to throw into the camera kit. But during production of the adhesive, maintenance people complained that the fumes sometimes reacted with liquid to form a hard shell that was nearly impossible to remove. No one made the connection at the time that this could be a good thing rather than a nuisance. With lackluster sales, Kodak sold the patent to a company that glued a hard hat to a steel beam with a squirming worker attached and the stuff sold out in stores.

Just who first realized that CA fumes could visualize latent prints in a closed environment as a deliberate act is still debated. But, as I mentioned, the initial procedure relying upon ambient temperature and humidity had limited application, particularly with multiple items. We all knew we needed some way to shorten the processing time. I contacted Kodak officially for more information about the adhesive and received a polite letter stating legal recommended against divulging any more information. In that era, Kodak supported law enforcement incredibly, and had a person assigned just to work with law enforcement in solving problems. The next time I saw the representative, I asked him what the letter meant.

His translation stated Kodak was worried such information might violate the protection of the sold patent or encourage me to tinker with the stuff that might result in Kodak's liability if I hurt myself. But he did tell me the origins of the CA adhesive, another example of dumb luck. At the time, Kodak was looking for a better adhesive to use for laminated windshields in automobiles. The bonding material had to have the same opitical properties as glass. A chemist placed a test compound in a refractometer and discovered the light bend was different. However, when he tried to removed the liquid, he found the material had hardened almost instantly and would not come out. The instant adhesive was born, but Kodak did not see the potential. (Kodak years earlier had told Dr. Land no one wanted instant photographs. Sixty years later, I guess Kodak was right.)

Frank found a disgruntled ex-employee who had no qualms revealing how to speed up the release. But a chemist thinks chemistry and recommended chemical heat. Someone like Menzel would laught at that and say what do you expect from people who talk about methyl ethyl chicken wire, his favor phrase to belittle chemistry. Finally someone noted that physical heat worked just as well without the mess.

I encourage you to pursue your quest to find true origins. I hope your encouragement to others is heeded. Rare are true products of directed research but nevertheless sometimes there is amazing brilliance in adaptation.

[8s0nc1]

Dear friends,
Please help me solve this problem:
After collecting the fingerprints by means of cyanoacrylate (CA) fuming, I dyed with rhodamine 6G. In the process of Fuming, white polime form on fingerprint clearly. However, after dying, the dye overlap fingerprint. At this time, we can not see fingerprint clearly . Is the dye too dense? So how do I solve this problem? Can I use laser 532 nm to illuminate this Rhodamine 6G dyed fingerprints?
Thank you so much.

[Tazman]

In the process of Fuming, white polime form on fingerprint clearly.

May I be so bold as to ask whether you photographed the white superglue residue before dye staining? And whether you have tried powdering the print?

Having learned photography several decades ago under Bob May in the days of 4" x 5" format cameras and CPO sheet film, I find almost no fingerprint that I cannot photograph clearly using an appropriate lighting technique of old. Since progressing from hard film to digital, the cost of film and developing has vanished. Capturing an image has shrunk from dollars to fractions of a penney. There is no excuse for NOT photographing a latent at every stage of processing. And with Photoshop, even the faintest of print can almost always be salvaged with enhancement.

I might also add that I am distressed at the disappearance of powder in the flood of technology. A few powders used correctly can do wonders on almost every surface, but since powder is the last step in the modern sequential processing routines, it seems to have fallen by the wayside. I see items over processed with new methods when I feel certain these same items would have yielded more and better latent prints with the judicious application of a suitable powder. I question whether a plethora of new chemical techniques are better than powder on many of the surfaces we examine.

Maybe one of the new folks has some ideas on how to recover the latent after dye staining. I would go back to traditional photography using creative lighting techniques, but maybe it's too late for that. Then I would try powder, but maybe it's too late for that, too.

[8s0nc1]

{May I be so bold as to ask whether you photographed the white superglue residue before dye staining? And whether you have tried powdering the print?......................................}
Thank you so much for respond.
I mean I can see the fingerprints after Fuming, but they are quite faint.So we dyed with rhodamine 6G and checked by laser to enhance it, to make fingerprints more clearly.I want to ask you (or somebody) some practical experience to do this.

[Diana Tabor]

Without knowing more about the print or what it looks like, one suggestion I have is to rinse the print with the solvent used in the R6G solution. Sometimes that helps differentiate a print from the background if the dye concentration is pretty high. Good luck.

[8s0nc1]

Thank Tazman, Diana Tabor, admin and everybody in this forum.