How do you tell if light is a blacklight?

Urine and other substances fluoresce under blacklight.

Turn off the light and hold it up to someone’s face, believe me you’ll know when it is a blacklight.

@pdworkin I believe you about the urine… but what’s something else that I could try? ;)

Laundry detergent.

OK that I’ll do.

Try a plain white T-shirt !!

Laundry detergent will work. Two of my friends were in bikinis and throwing it at each other at a black light party. Looks fun. :)

Anything white will flouresce under a blacklight (it’ll glow a navyish hue).
Try what @pretty Lilly said it’s wild… Check out their teeth and the whites of their eyes!

Is that “DNA” stain you swore you got out of your shirt months ago lighting up like a thousand raging suns?

If so, then it is a blacklight.

You can check it with a photospectrometer, but they are not a household item. They tend to cause color shifts, especially the lighter colors.

My rule of thumb is that if the light makes my eyeballs feel like they are in a vise, it’s a blacklight.

well semen should glow in the light….. try putting some of your bodily fluids under it and see what happens.

I tried it with the laundry detergent. It is a blacklight! wow!