[thedoc (OP)]

One thing you should never do to liquid nitrogen is to seal it in a pressure vessel.... so we had a go.

 Read more about this experiment.


Garage science is a blog of science experiments you probably can't or shouldn't do at home

 

[techmind]

You can do a less dangerous version of this experiment using a plastic (polythene) supermarket milk bottle. It bursts at rather lower pressure, so is safer.
Indoors (in the lab) it still makes a very satisfactory bang however!

I wondered whether you should have made a warning about the amount of nitrogen to use (you said about 2inch depth (50mm) on the podcast): too much and you risk it exploding too soon (and freezing your hand while putting the cap on), too little and it may build up dangerous pressure but fail to explode (then what???).

[Raghavendra]

 It's very dangerous and should be carefull

[daveshorts]

Unless you really fill the bottle to the top it is going to take a while to explode, as a lot of nitrogen has to boil off before it goes bang. The first part of the video was slowed down a lot - it took about 4 minutes to go off.

But yes this is very dangerous, don't do it...

[Robb]

It is so funny you can watch the cap flying toward you...

[Ray Sacks]

Potentially this situation could happen in many places in a plant designed to make and handle cryogenic liquids - like liquid nitrogen.  Try the experiment again but put a "thermal relief valve"(PSV) in the cap - this is how engineering makes science practical. The PSV could be a baloon (or paper etc) held over the mouth with an elastic band in place of the plastic top... Or it could be a 'real' thermal PSV (pressure safety valve).  

[Gord]

I made a dry ice bomb at home once (before I realized how dangerous it was) but I didn't use any water. It took over 30 nerve wracking minutes to explode. It was fun to watch the dry ice melt (through a pair of binoculars) well before it exploded.