Product: Toy
Air Pen   (+4)  [vote for, against]
Write in midair!

A handheld "pen" or lightweight pump that, at the push of a button, ejects a steady stream or jet of colored gas from its tip. This gas has the exact same density as air, so it hangs in midair without rising or sinking. Potentially, in an environment without any air currents, one could write or draw in midair.
-- DrWorm, Aug 04 2009

floatfoam floatfoam
[xaviergisz, Aug 04 2009]

What stops the gas from moving after being ejected from the pen?
-- tatterdemalion, Aug 04 2009

Very careful blowing.
-- DrWorm, Aug 04 2009

would need to be a long pointer to work, not a pen... but neat [+]
-- FlyingToaster, Aug 04 2009

random, halfbakery