Originally Posted by
Cheshyre
there's an easier way. just buy a can of compressed air (for computers) and turn it upside-down and start spraying the propellant at the dent, and it'll frost over just as fast. plus, you don't have to steal compressed air.
i dunno. i work in a research lab with a huge box of dry ice at the door, and i still think it'd be difficult to just steal a piece and transport it across town to a bike rack. i can't even imagine doing that with liquid nitrogen, and trying to transport a sloshing liquid o' death about a mile and a half across campus.
Nitrogen boils at -192°C, that's probably cold enough to make steel pretty brittle.
Dry ice is CO2 and boils at -72°C... might have a little effect on the properties of steel.
Compressed air in a can will have no where near that effect (I realize you're talking about car dents and not U-locks); and there is no propellant other than the air itself.
Sometimes you hear stories about thieves using the nitrogen freeze... I'll wager it's never happened.