Why can black lights spot s***n stains?

Question

Why is it possible to look at a piece of fabric under a black light and spot s***n stains? And would you have the same success if you examined a surface like wood or tile?

Answer 1

The surface makes no difference at all. Substances or materials that contain Fluorescent molecules can be seen under a black light.

Check out the link below for an explanation...

Answer 2

Good science fair project

Answer 3

its because the black light is exactly that....black anything lighter appears to glow....also anything that has high amounts of protein will glow bright purple.such as s***n urine or blood.

Answer 4

ok, it's not just s***n stains, they bring out a lot, and it's because black lights use ultra violet light, light which is not visible to the naked eye which is why it's refered to as "black" light, anything that is a lighter color than what surrounds it will show up much brighter, and yes it will work on wood and tile and just about any surface, UV light massively emphasizes contrast, which is why you can see just about anything on the surface of something with it.