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Will urine show up under UV light?

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Will urine show up under UV light? What other bodily fluids? I'm into forensics. If urine dries without a smell or stain, is it gone?

Rob from Forked River, NJ


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By ryan (Guest Post)04/23/2007

Ive heard that UV light works in different frequencies however, and not all standard UV tubes emit the right kind of frequency to show up dog/cat pee.

Could be just rubbish put about by sellers of UV tubes though to make you buy their product instead of others.

Editor's Note: Carpet cleaners use a black light to looks for places where pets have peed. See if you can find a black light.

By Mary [12]12/18/2006

Yes, as well as other bodily fluids and quite a few other interesting uses.

A tube black light is a basically a fluorescent lamp with a different sort of phosphor coating. This coating absorbs harmful shortwave UV-B and UV-C light and emits UV-A light (in the same basic way the phosphor in a fluorescent lamp absorbs UV light and emits visible light). The "black" glass tube itself blocks most visible light, so in the end only benign long-wave UV-A light and some blue and violet visible light pass through.

The emitted UV light reacts with various external phosphors in exactly the same way as the UV light inside a fluorescent lamp reacts with the phosphor coating. The external phosphors glow as long as the UV light is shining on them.

In addition to making people and fluorescent posters look cool, black lights have some practical applications. For example:

Appraisers use them to detect forgeries of antiques. Many paints today contain phosphors that will glow under a black light, while most older paints do not contain phosphors.

Repairmen use them to find invisible leaks in machinery -- they inject a little fluorescent dye into the fuel supply and illuminate it with a black light. For example, they might detect an invisible air conditioner leak by adding fluorescent dye to the refrigerant.

Law enforcement officers can use them to identify counterfeit money. The United States and many other countries include an invisible fluorescent strip in their larger bills that only shows up under a black light.

Forensic scientists use them to analyze crime scenes. To pick out fingerprints, for example, they often dust with fluorescent dye under a black light. This makes it easier to pick the fingerprints out from surrounding dirt.

Black lights can also identify bodily fluids that naturally fluoresce, making them indespensible in odor removal and cleaning.

Most of these uses, as well as dozens of others, follow a common theme -- the black lights make the invisible visible or isolate one specific substance from everything around it. When you think about it, there are dozens of situations where you could put this phenomenon to work. The applications are potentially endless!

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