G'morning David,

 DW> That would be true if the can were absolutely full
 DW> of liquid. But I'm sure that, in most cases at least,
 DW> there is some gas at the top. That's why an unopened can
 DW> makes a sloshing sound if shaken. The gas is compressible,
 DW> so the can can be compressed at least slightly, if enough
 DW> pressure is applied. But, since the gas is at quite high
 DW> pressure, this is not easy.

In the `60's here in New Zealand, drinkers used to bring a half- 
gallon glass jar to their pubs to be filled up for consuming at 
home, and every tram and bus heading into the suburbs after 6pm 
would see 10 or 20 of these things being carried aboard.

The odd one would explode, and an enquiry by a columnist (Noel 
Holmes) and I soon determined the cause;  if the owner was really 
determined to have his money's worth, he'd get the barman to fill 
the thing right up.

This left no air gap for escaping carbon dioxide to expand into, 
creating enormous pressure that forced the smallest flaw in the 
glass to fail - leaving many a frustrated drinker clinging to a 
paper bag full of glass shards and half a gallon of liberated 
beer.

I think you'll find that all contained drinks have an air gap for 
safety reasons.

The history of contained drinks in New Zealand follow your trails 
of corked and capped bottles, `crown' topped bottles, steel cans, 
aluminium cans .... with tracks leading off into screw-topped 
glass wine bottles and screw-topped PEP (?) bottles.

Pet food cans here are aluminium (small) and tin (large),  and 
beans, vegetables and food containers vary between glass, tin or 
steel.

Miles.   
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