These baby torches for our trade there is such a small hose size
and orafice size that I don't think you could make an explosion
happen, besides filling a balloon with oxy-propane and igniting it
with a cigarette on a long stick, which I don't condone but would
have to watch if it was happening near me. ;).
In the late 70s/early 80s, I worked for a retail store in the
Fairlane Town Center mall in Dearborn Michigan (store is now long
closed). Ours was, I think, one of the first of a trend of stores in
malls, where a certain percentage of merchandise was made in shop,
and of course, the usual range of repairs and custom work, but unlike
most stores, our shop was right out front, with windows to the mall
so passers-by could watch us work (or pretend to). It was a bit like
working in a fish bowl, with resulting temptations. Occasionally,
there'd be boredom, which we young fools would take advantage of.
Baked apples in the burnout oven, or pretending to be taking a phone
call, chatting on the phone while pretending to solder something on a
ring while customers on the other side of the window watched.
Distracted, the ring would start to melt into a puddle with customers
sometimes trying to call our attention to the disaster in front of
them (It would be a scrap ring, of course). Then there were the
quarters soldered to a tack, and hammered into the linoleum tile out
front, so we could watch people try and pick them up. But one such
stupid stunt we only tried once, was just what you describe. We were
running acetylene and oxygen in Little torches, with a Meco Midget
for casting. Set the oxy/acetylene mix to neutral on a little torch,
dip the tip in a glass of water to extinguish the flame without
changing the valves, and fill a small ziplock bag with the mix.
Seal, set it on the floor, and hit it with the relit torch. All in
the name of science and curiosity, of course. The resulting bang was
REALLY loud. Apparently, mall security, located just around the
corner from us, was convinced they'd heard a gunshot. Probably a
bunch of them no doubt; and came racing around the corner to the
store, guns drawn, perhaps expecting a gunfighte!! Needless to say,
we had a bit of seriously white lie to invent real fast. And we
didn't do that again.
The wonder of all these stunts is that we kept our jobs. Maybe it
was just the times, or maybe, unbeknownst to us, either the boss was
just as much a cutup kid at heart as we were, or we were good enough
goldsmiths when not screwing around, that he forgave us. Memories...