Mid pressurization. Small leaks mean that when you stop pumping vapour inside condenses, as soon as you start pumping it disappears in about 2 pumps. It's fascinating to watch.
A coke bottle after about 160psi. Even a small amount of heat (hairdryer) causes it to deform, and it has none of it's normal elasticity when you squeeze it. Repressurizing it brought back to this bulged state.
The best (loudest) bottle I tested. It's one of the smooth walled ones available in boots. This lack of imperfections meant it bulged around 120 and blew at ~140 It made my ears ring slightly through earplugs, and I felt the concussion!
The re-usable burst disk lucozade bottle*. I cut a hole in the lid and used plastic as a burst disk. Only tested it to around 100psi when the lid broke, but sounded good, a fair gunshot crack. I plan to test it with tougher burst disks and see how it compares to a whole bottle. Plastic and Al foil aren't really strong enough. Can anyone suggest anything similar that might work? The diameter of the opening is about 2cm and anything too thick means the lid can't screw on properly.
As for the safety of using fizzy drinks bottles as chambers, I reckon they're pretty safe up to 100, then ambiguous to 140, then dangerous. Even past 160 I couldn't get it to burst, despite the swelling. I removed it from the pump (probably dropped to about 150psi) and threw it to the ground - nothing. I then threw it with all the force I could and the lid blew. The bottle itself crumpled on what I assume to be where it hit the ground but I'm not totally sure. The lid had split completely and the schrader was nowhere to be seen.
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