A note about acetylene, if I may.  First, acetylene has to be dissolved
in acetone when under pressure or it will explosively decompose.  This
is the main reason MAP has become common.  MAP, which is stable acetylene
(methyl acetyl something or other), can be stored as compressed gas
safely.  MAP has almost the same energy content as acetylene without
the hazards.  Propane doesn't have near the energy content of MAP, and
in fact does not have the energy content of gasoline (some of you may
remember the old gasoline blow torch).

Just my $1.50 worth (when adjusted for inflation).

Jim Cook