Forensic Light?

[Undark]

Hi,

I keep wondering how forensic lights work.
You know, that kind of light that shows traces of blood etc. better
than normal daylight. The Arc4+ is available in a
"forensics kit" which does exactly what I mean.

It appears to me that those forensic lights are a near-UV
illumination source and the effect of highlighting
body fluids is achieved by a colored filter (special
goggles). However on the website for the Arc4+ forensics
kit those goggles only have a sign "UVShield" on them
and it seems that those are only for eye protection...

Can anyone explain to me how a special light can improve
vision of substances that are not visible with the naked
eye without using chemicals?
Would it work to take an near-UV counterfeit money checker
and a orange filter or UV-filter?

Thanks!

[Steve_Chism]

I can't explain exactly how blue light causes blood, amongst other bodily fluids, to "jump out," I'm not a scientist :P but I do know that hunters use blue light to track wounded deer/antelope/etc.

forensic teams use the blue light to find traces of blood, fluids, etc...that's why they use the orange goggles -- blood and bodily fluids can be seen easily with just intense blue light but when you're looking for small trace amounts that can't be seen as easily with the naked eye, the orange tint helps somehow.

As far as my understanding goes, the goggles aren't 'special' filters, they're just orange tinted polycarbonate that have some UV protection, but I may be wrong. Someone with a good understanding of the light spectrum, etc. would probably be able to give you a more detailed answer, but hopefully I answered your question [img]/ubbthreads/images/graemlins/smile.gif[/img]

Steve

[PhotonWrangler]

There are several law enforcement officers on CPF that can probably chime in with firsthand experience, but I believe that the suspected area is sprayed with Luminol, and it's the Luminol that reacts with traces of blood to form a substance that fluoresces under longwave UV (black light).

[dano]

I've never seen one of those blue lights used at a crime scene.

-dan

[PhotonWrangler]

Sorry, my bad. I was thinking of another substance, Fluorescein. Luminol emits it's own light when it comes in contact with blood.
Here's a story about it...

[Undark]

Thanks for your input so far.

I did some research on the web and found the following
article: http://www.forensic.e-symposium.com/...2003/oct3.html

Although it seems to be written in favor of a company it
contains some useful information.

[Blackbeagle]

Near UV or UV light reacts with substances within biological fluids causing them to fluoresce. The UV energy gets absorbed and re-radiated in visible light spectra. The UV filter goggles are there to: 1. Cut the UV bouncing back into your eyes to protect you. (Without it, intense exposure causes the familiar "sand rubbed in your eyes" feeling. That's UV damage making itself felt.) 2. The filter also cuts back on the near UV radiation. Since most of the lights send out either an intense deep blue or violet light along with the UV, the orange of the goggles cuts this out. Otherwise the small amount of fluorescense may get lost in the blue or violet glare.

BTW: I read somewhere that you could use a normal flashlight with at least 35K candlepower. Filter over this using a Kodak/Wratten 47B deep blue filter. Darken the area and view through blue-blocker or amber glasses similar to those used for shooting protection.

[Steve_Chism]

[ QUOTE ]
(Without it, intense exposure causes the familiar "sand rubbed in your eyes" feeling.

[/ QUOTE ]

Does this mean that it wouldn't be a good idea to use the forensic Arc4+ as an EDC light?

[Undark]

Steve, I don't know what wavelength the light has
but if it is below 380nm you should avoid exposing it to the eye.
Below the 380nm there are UV-A, UV-B and UV-C.
Looking into a light that emits UV-C can damage alot in
"the blink of an eye" [img]/ubbthreads/images/graemlins/grin.gif[/img] even though you can't see the light.

While it is rather improbable that the Arc emits thost kind
of rays it could contain some rays of the UV-A spectrum
which are not that dangerous but looking straight into
such a beam doesn't do any good.
However, if it is dangerous it will be stated. Most of near-UV
lights have a warning sticker on them.

As for EDCing such a light: If it is a near-UV-type it won't
be of any use for general EDC. Well, you could
check money with it or use it as (what it is) a forensic
light. But that are really specialized tasks.
The near-UV-light is a really dim purple which is only reflected
by special substances.
Lighting up a room or objects over large distances can't be
done with a near-UV one. Think about those "blacklight bulbs".
You got the same effect with near-UV-LEDs.

However, it may be that the forensic Arc doesn't use near-UV-LEDs
but simply special blue ones. If that's the case all of the above
doesn't apply... of course you have to decide if you'd like
having pure blue light on your EDC flashlight...

[Undark]

Blackbeagle, I'll try the blue-filter thing.
It'd be great if it worked because with an ordinary flashlight
and a colored lens there won't be any harmful radiation.

However, I'll also get one of those 380nm LEDs and check if
there's any reaction when shone on some piece of dirty carpet.

We'll see...

[Steve_Chism]

Peter told me it is at ~665nm, sounds safe to me?

[The_LED_Museum]

665nm is deep red; I think you meant to type "~465nm", which is blue, bordering on "dental blue". [img]/ubbthreads/images/graemlins/wink.gif[/img] [img]/ubbthreads/images/graemlins/smile.gif[/img] [img]/ubbthreads/images/graemlins/wink.gif[/img]

[Undark]

Steve, like I said: The critical region is the UV-A,B,C wavelength.
Those three are below 380nm. Everything above this value
should be safe.

LED_Museum, I read your article on the 380nm LED from
Roithner and ordered it. In your review it seems to be
the right one for forensic applications. On the Roithner
website they stated that money checkers with this wavelength
are the only ones that are able to identify the security
features of the euro currency.

These are at least two reasons to go for 380nm. However,
that close to the UV-A spectrum I'll need eye protection or
is this still safe?
Can you tell us a bit more on the things that did glow in
that kind of light?

[The_LED_Museum]

[ QUOTE ]
Undark said:
Can you tell us a bit more on the things that did glow in
that kind of light?

[/ QUOTE ]
I'm guessing I received that LED at least a couple of years ago, so I don't know what else will fluoresce, or even where that LED is right now. Sorry about that. [img]/ubbthreads/images/graemlins/frown.gif[/img]

[chuck30mi]

UV light causes semen to flouresce, best seen in a dark room. UV light also causes mouse urine to flouresce, so a UV light is useful to see if you have mice in your house. They pee whereever they walk.

[Aloft]

Having gotten interested in cryptology and steganography ("hidden writing") I embarked on a search for various formulae for invisible inks. Not much was written about flourescent materials, at least that I found. But I did find a couple interesting companies making such compounds. I have no connection with the companies, but got good service when I dealt with them. . .

Shannon Luminous Materials. . .made various inks and powders. They actually also had crayons that would flouresce in various colors, including red (rare, I think).

Ultra Violet Products. . . various inks and powders

Maxmax.com. . .various lights, inks, and powders, including one that will dissolve in acetone, and flouresces bright red.

Some stuff around your house may flouresce unexpectedly too. Most laundry detergents with "whiteners" actually sort of dye your whites with a material that flouresces under UV. That makes it look whiter when in sunlight. Making a solution of this was suggested to me for making a cheap invisible ink, instead of paying big bucks for the premade stuff.

[PhotonWrangler]

[ QUOTE ]
Aloft said:
Some stuff around your house may flouresce unexpectedly too. Most laundry detergents with "whiteners" actually sort of dye your whites with a material that flouresces under UV. That makes it look whiter when in sunlight. Making a solution of this was suggested to me for making a cheap invisible ink, instead of paying big bucks for the premade stuff.

[/ QUOTE ]

Yup, plain old RIT "Whitening" dye, available at most drugstores and many supermarkets, is the UV dye in concentrated powder form. Makes a cheap source of UV ink.

Thanks for the info about the other sources for UV inks and powders. That red formula is truly unique!

[The_LED_Museum]

[ QUOTE ]
Aloft said:
...Most laundry detergents with "whiteners" actually sort of dye your whites with a material that flouresces under UV. That makes it look whiter when in sunlight.

[/ QUOTE ]
This material is usually called "bluing" or "blueing", and is added to wash soap specifically because it fluoresces rather strongly a whitish blue, so your "whites" look whiter in sunlight or other light with UV content.
The more UV the light has, the whiter the garment washed in that soap will appear.

[PhotonWrangler]

Here's a link to RIT's "Whitener & Brightener" dye. Scroll down just a bit to see it.

[Aloft]

[/ QUOTE ]

Yup, plain old RIT "Whitening" dye, available at most drugstores and many supermarkets, is the UV dye in concentrated powder form. Makes a cheap source of UV ink.

Thanks for the info about the other sources for UV inks and powders. That red formula is truly unique!

[/ QUOTE ]

Actually, Photonwrangler, I should be thanking you. I've been looking all over for a cheap source of the plain old whitener that they use in detergent. . .I didn't realize that RIT Whitening Dye is the stuff, to do with just what you said, make a cheap, non-toxic invisible ink! I've done web searches, downloaded MSDS's, found out where I can buy it from China in 50,000 gallon lots, etc. And here it was just waiting for me to come in and buy it. I'll check my local pharmacies, but if you know of a chain that carries it, PLEASE let me know by post or PM. Amazing what I've found out on(and how much money I've spentbecause of) the CPF.

[PhotonWrangler]

Walgreen's carries some of the RIT line. I'm sure you can find it at Wal-Mart and probably at K-Mart also. The drugstore chain in these parts is local, so I don't think you'll find this store in Washington state.

BTW, RIT also sells their stuff in bulk packages online, so if you ever need to make a million gallons of the stuff, you'll have a source for larger quantities of the dye.

I checked the MSDS for this product on their site, and they only list "organic and inorganic compounds" as the ingredients.

[Draco_Americanus]

If one wishs for flourescent things I recomend flourescent rocks and minerals, not quite as usefull as dies but still colorfull. sadly though most need a UV-C type light to be the best.
As for safty glasses for UV-A I would say IMHO that they are overkill and not needed for lowered power light sources. still I would not make it a point to stare into a UV-A light source for long amounts of time. UV-B and UV-C, thats a diffrent animal. I have a UV-C light that I put togeather My self and learned very fast that even a 15 watt light can mess one's eyes up in little time, But the UV-C is easy to filter out. Normal safty glasses that I get from work filter out UV-C. Plexi glass, normal glass even filters it out.
The UV leds seem to make the strip in money light up nicely as well, filters it out. postage stamps are also sensitive to UV-C, they turn a yello color.

[Blackbeagle]

Just to toss this out - Sanford, the maker of the Sharpie pens, also makes a product call a Security Marker. Just like a regular Sharpie pen excepts uses a clear ink that goes on virtually invisibly and flouresces under UV. Relatively easy to get (at least here.)

Well, I recently purchased a UV flashlight for about 35 dollars. I bought the batteries, shined it on the toilet seat in the dark, and came up with nothing (and no, this toilet isn't cleaned constantly. I just thought it would be a logical place to try it out. I didn't use the goggles because from what I'm reading, it seems to be more for protection than detection.

Am I missing a step? Is there a kind of powder or dye that will cling to urine, blood, semen, etc?

Thanks.

[Draco_Americanus]

urine should show up very well under uv with nothing else. Atlest mine does. I made the mistake of taking a flourescent blacklight into the bathroom, I was horified!! I usaly wash after peeing and there was still urine on the walls and even the lightswitch! Needless to say I cleaned the bathroom while the uv was on!
The urine was a yellow to orange color all the dust was bright blue.

so maby there is something wrong with the light? or it does not go into the UV band enough?

[Aloft]

I've seen urine flouresce a pale green with my LED based UV light. From what I understand, LED based lights are usually 375-400nm, so lower wavelength UV's may be more effective. I didn't use any additives or other chemicals, though maybe some cleaning fluid contributes to the reaction.

BTW, I finally managed to get some RIT "Whitener and Brightner" at my local Bartell's Drug Store, a chain I believe is local to the Seattle area. Mixed it up with some Isopropyl Alcohol (91%). It didn't dissolve too well, probably because I used too much powder in too little alcohol. It dried invisibly on a white 3x5 index card (don't use cards or paper that are superwhite. . . they're treated to flouresce themselves, and your writing will still be invisible!), but flouresced very prominently under the light of my Inova X5 UV flashlight. Very cool, and way cheaper than buying the ink. Thanks again for "discovering" that for me, PhotonWrangler!