He was very clear about dipping my hand in slowly, and not moving it at all, as that would’ve shaken off the boundary and resulted in frostnip - but this was the 90’s, when getting kids to put their hand in cryo was just one of those things you do.

Just don't leave your hand in there for too long.

And try to avoid any liquid nitrogen droplets getting caught between your shirt cuff and your wrist (cold burns hurt)

OA: I shall miss Dr Wolf.