Desde ThinkGeek directamente la información (en inglés):

It’s the dead of night and everyone is tucked in bed and the owls are
a-hootin’. So it’s time to break out the Glow Graffiti! Powered with UV
light the Glow Graffiti lets you write, stencil and draw rude pictures
to create your very own glowing light show. It’s like very complicated
vandalism except much prettier and you won’t get nicked by the police
doing it. This really is a gadget of mind-boggling genius, perfect for
parties (or if you’re nocturnal, for late-night artistic inspiration)
and will have your friends intrigued as to how it all works.

The UV light coming from the can excites luminescent material in the
special photo sensitive sheet. To create tight lines spray very close,
or spray from 12” for larger areas and stencils. Simply twist the nozzle anti-clockwise to access the battery compartment.

Aerosol-style can with a sheet of re-usable light-sensitive material

• Designed to be used in the dark
• Graffiti will completely fade from the sheet in less than one hour
• Takes two AA batteries (not included)
• Dimensions (spray can): 2.5” x 6” (6.5 x 15cm)
• Dimensions (sheet): 24” x 24” (61 x 61cm)
• Includes: light can, light sensitive sheet, instructions, alphabet stencil
• Do NOT shine directly into eyes (emits UV light)

Realmente Geek…