UV Lights for Seal Inspection

Ginseng

Banned
This is a brief article on portable UV light sources that can be used for detection of the Cuban coat of arms (COA) on the warranty seal sticker found on all boxes of Cuban cigars since early 2000. Here is a photo of the central portion of the seal sticker where the COA is found taken under neutral white compact fluorescent lighting.

(IMG:http://i61.photobucket.com/albums/h73/Gins...ientLight01.jpg)

The key variable in determining whether a source will render visible the COA is the wavelength of the emitted UV radiation. In the past, I only knew enough to say that "long" wavelength UV worked and "short" wavelength did not. And it even took some work here and here to get to that point. Recently, I found an online source for beyond-visible (UV and IR) lighting used in forensic work. In speaking with the principal of that company, I learned three things. First, 395 nm "longwave" LED lights such as the Inova X1 UV were "too long" and did not work at all. Second, the cheapo handheld UV tube lights work well because these fluorescent UV tubes have an emission peak around 370 nm. Third, and most important, that the longwave UV that worked was actually in the range of 365-385 nm. As you see from the Wikipedia article I linked above, all of the wavelengths we're talking about actually fall into the near UV portion of the spectrum.

My source of choice, thus far, has been a $20 tube unit such as is used for detecting pet urine stains on carpet and other nasty residues. It works supremely well, is fairly portable, and produces a very smooth beam. The only knocks against it are that it takes 4xAA batteries and is highly susceptible to damage if dropped. As you can see, it floods the entire seal sticker with a powerful and uniform bath of UV light and the fluorescent COA really pops right out. This high contrast is a result of significant emissions right in the range of the UV fluorescent dye used in the COA ink and the uniform nature of the beam of light.

(IMG:http://i61.photobucket.com/albums/h73/Gins...UVTubeLight.jpg)

Although the tube lamp works very well, it's a bit of a pain to lug around and you definitely look the geek if you whip it out at a herf (which I have done). Well, now there is an alternative. A company called Xenopus has just recently released a pen-sized pocket light that has an emission peak between 380-385 nm which puts it in the range required to excite the UV dyes in the COA ink. Here is a photo of the same seal area illuminated by the tightly-focused beam of the penlight. You can see that the area where the COA is found is lit up with the longer wavelength portion of the output giving it a bluish appearance. Contrast is still good though not quite as high as with the tube lamp. This light is convenient, rugged, and dare I say, even cool with its matte black barrel. Since it's a small unit, it is not nearly as powerful as the tube lamp and so the results may be difficult to see in daylight but under normal room illumination, it does what we would want. Look for this item (#XeUVPen) under the "Security" and "Keychain" product categories.

(IMG:http://i61.photobucket.com/albums/h73/Gins..._385nmUVPen.jpg)

This final image is a comparison shot of my tube lamp and the new UV penlight. To be sure, there are other compact UV lights out there that emit in this wavelength but they are not as convenient as they use button cells. See here and here. The foil-looking band along the side of the tube chamber is aluminum tape I applied to redirect the side radiation and send it to where I need it.

(IMG:http://i61.photobucket.com/albums/h73/Gins...ht_385nmPen.jpg)

So there you have it. If you like this kind of stuff or come in contact with 2000 or later Cuban cigars, then get yourself one of these and have a ball. Just keep in mind that even having a light doesn't mean proper determination of correctness is easy to do.

Wilkey
 

Jam1173

New Member
great read...

You always have such great information for all of us trying to learn about this stuff.

Thanks for all you do
 

handyman dave

Newbie - Still old but not dead yet!
Thanks for being so willing to share and so thorough and effective in doing so.
I really appreciate it! :thumbs:
 

sinnyc

Tibi ipsi esto fidelis.
Thanks Wilkey for bringing this all together.

I completely forgot about our interrupted discussion on this a few months ago. I did end up with a rugged 7-LED flashlight style unit that also uses a suitable wavelength and wroks prety well in addition to a tube-style light similar to yours that works very well but is, as you mention, fairly delicate.

- Tim
 
Thanks, Wilkey. I've found my dermatology UV light to be effective, although it has a slightly longer wavelength. Also good for picking off tomato worms at night.

Slightly off topic, has anyone noted COA ink to be faintly visible under incandescent light? A faint golden color? Seen this on one stamp only.

George
 

Ginseng

Banned
Thanks, Wilkey. I've found my dermatology UV light to be effective, although it has a slightly longer wavelength. Also good for picking off tomato worms at night.

Slightly off topic, has anyone noted COA ink to be faintly visible under incandescent light? A faint golden color? Seen this on one stamp only.

George
The only cases I have seen where the COA has been visible at all under visible light have been on counterfeit boxes. I have several like that. The ink laydown is too heavy and sits on top of the paper and thus you can see it as a reflectance difference when you view the sticker at a glancing angle.

It's not impossible that you get some mild fluorescence due to UV components from an incandescent lamp, but I'm guessing the luminance (brightness) of the COA would be drowned out by the overall brightness of the sticker.

Wilkey
 

ckeller52

"All the Twitters. I know them."
Got one two days ago and it works great on the RA's and SLR but point it on a Quintero Brevas label and I get nothing. And the box is from a trusted source. Or, maybe not so much now. :whistling: The labels on the Partagas cardboard display pack doesn't light up the shield either.

Plug in my florescent UV and they are there but faint.
 

drew_goring

Big Bad Mother F*cker!
Got one two days ago and it works great on the RA's and SLR but point it on a Quintero Brevas label and I get nothing. And the box is from a trusted source. Or, maybe not so much now. :whistling: The labels on the Partagas cardboard display pack doesn't light up the shield either.

Plug in my florescent UV and they are there but faint.
Don't rule out a vendor just because the seal doesn't sparkle the way it is supposed to. Remember, this is Cuba we are talking about. Not exactly the pinnacle of quality control. ;)
 

ckeller52

"All the Twitters. I know them."
Oh no, I'm not ruling them out, not at all. Besides I know where they came from I've smoked some. :thumbs:

But you're right about the QC It's way different from label to label.
 
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