Semen visible under a black light

[snopes]

Comment: There is an urban legend floating around that sperm/semen that
has dried on something is visible under a black light.

Sometimes the story is a "gross out" kind of tale about hotel bedspreads,
chairs and/or sofas in the rooms to warn travelers.

Other times it is a "cautionary tale" which typically involves some young
lady entering a situation where a black light is present and her previous
escapades are revealed to coworkers or her boyfriend/husband.

I have even seen this scenario as a British detective skit which
incorporates both - a detective is looking for clues about a suspect in a
hotel room using a black light, his young, pretty female assistant enters
the room, and the black light reveals glowing, tell-tale signs on her face
and hair.

I haven't had a black light since college (which is longer ago than I'd
like to admit) to test this. However, I suspect the reality has no basis
in fact, but rather these tales are circulated to warn people about
certain types of behaviors.

[missy_pooh_1997]

Isn't that what they've done of Dateline a ton of times in hotels? They say it's supposed to show any bodily fluid.

[Syllavus]

I know that soap is highly visible under a black light. I actually did a project in college where I used liquid soap (a generic brand of Wool-Ite) as ink to screen print stuff on a bathroom wall. It was invisible until you turned the black light on. I experimented with lots of different types of soap to find which one glowed the best.

[Towknie]

Originally Posted by Syllavus

I know that soap is highly visible under a black light. I actually did a project in college where I used liquid soap (a generic brand of Wool-Ite) as ink to screen print stuff on a bathroom wall. It was invisible until you turned the black light on. I experimented with lots of different types of soap to find which one glowed the best.

As is spray in carpet stain remover. We drew all kinds of nefarious designs in the carpet in college that came out to play on Friday nights.

[Nick Theodorakis]

Originally Posted by Syllavus

I know that soap is highly visible under a black light. I actually did a project in college where I used liquid soap (a generic brand of Wool-Ite) as ink to screen print stuff on a bathroom wall. It was invisible until you turned the black light on. I experimented with lots of different types of soap to find which one glowed the best.

Some detergents have fluorescent compounds added to them to make clothes washed in them appear brighter in sunlight.

Nick

I have a blacklight. If desperate times call for desperate measures and we can't resolve this, I'll bravely volunteer to perform a highly scientific study and advise of the results.

[Mycroft]

I think they are confusing it with crime scene programs when they detect minute traces of blood using a UV light. The secret to it (often a stage left out in the programs) is that the whole area is sprayed with a chemical (usually Luminol) which flouresces under UV when in contact with iron compound, eg hemoglobin. Unfortunately it will not work with most other body fluids as the usually do not contain hemoglobin.

[CannonFodder]

Originally Posted by Class Bravo

I have a blacklight. If desperate times call for desperate measures and we can't resolve this, I'll bravely volunteer to perform a highly scientific study and advise of the results.

Don't bother (unless you really want to). It works, and no I will not be posting pictures.

No, I didn't really want to. And thanks.

[Brad from Georgia]

{Peter Lorre voice}A-heh! Dot's de way horrible mutant monsters are created. A-heh!{/Peter Lorre voice}

[snoozn]

When we lived in an apartment and complained about the bad smell, the manager sent a guy with a black light (I'm pretty sure it was a black light) to check the carpet and sure enough there were all the stains that weren't visible without it. The black light guy said they were probably cat pee (which would match with the smell). Don't know if he knew what he was talking about or if it works for all "bodily fluids".

snoozn

[geminilee]

Originally Posted by Nick Theodorakis

Some detergents have fluorescent compounds added to them to make clothes washed in them appear brighter in sunlight.

Nick

UV blockers... anything that says UV blocker will glow under a blacklight. Bleached hair also glows, so if you are wondering if it is natural or a dye job, head to the club.

[Dr. Winston O'Boogie]

Originally Posted by Class Bravo

I have a blacklight. If desperate times call for desperate measures and we can't resolve this, I'll bravely volunteer to perform a highly scientific study and advise of the results.

Don't do it! You've already given so much for this country, being in the air force, working as an air traffic controller to the detrement of your health! Let some other brave soul do this!

Wasn't there an episode of ER when they brought this one up? I think it was Susan wearing Deb (Dr. Chen's) sweater and coming into a room where Abby was using a black light. They asked Deb about it and she said that it was just club soda, which (supposedly) glows just as semen is supposed to.

Sadly, this was the first thing I thought of when I read the title of the thread.

[Arts Myth]

There was also the scene from Basic Instinct (the scene that didn't involve Sharon Stone and a cigarette, although neither scene involved underwear, either), where they were checking the bed for signs of, um, activity. There were a few. And not just on the bed, IIRC...

[chelle]

Originally Posted by snoozn

When we lived in an apartment and complained about the bad smell, the manager sent a guy with a black light (I'm pretty sure it was a black light) to check the carpet and sure enough there were all the stains that weren't visible without it. The black light guy said they were probably cat pee (which would match with the smell). Don't know if he knew what he was talking about or if it works for all "bodily fluids".

snoozn

Cat pee does glow under a black light. So does ring worm if anyone's curious.

[ganzfeld]

I remember Jeanne Moos did a segment where she went into a hotel/motel room with a man who had a UV light and was an "expert" on all of the stains. She edited it so that they were both looking at an unknown stain and she asked him: "But can you be sure?" To which he replied, something like, "I've been doing this for quite some time. I know urine when I see it!" It was a very funny clip. But anyway, yes, just about every stain glowed.

[KirkMcD]

Originally Posted by snopes

Comment: There is an urban legend floating around that sperm/semen that has dried on something is visible under a black light.

I just saw them doing this on a repeat of CSI. It wasn't a black light though. It was some other wavelength and they were wearing goggles to see the stain.

[snopes]

A variety of substances fluoresce under black lights, so how would anyone know for sure that what s/he was looking at was semen? One might be able to make an educated guess based on the location and shape of the spot, but I think that's far from definitive.

- snopes

[Richard W]

Originally Posted by Towknie

As is spray in carpet stain remover. We drew all kinds of nefarious designs in the carpet in college that came out to play on Friday nights.

So do some artificial fibres. I had a cheap DJ in college that had some sort of wool / artificial fibre blend, and although it looked fine in normal light, under UV it made me look as though I had luminescent dandruff. It took me a while to work out that I didn't have luminescent dandruff - obsessively trying to brush the little glowing spots off your shoulders is probably quite unattractive in all sorts of ways...