Hi Alma, I use butane and oxygen for casting silver. It works fine.
On my torch handle there are two knobs, one for ox and the other for
butane / acetyle ne. If I turn the butane gas on only, I get the same
effect as you: kaboom & soot. To avoid that, I also open a little for
the oxygen, when I ignite t he torch. You say that your torch outfit
is called —acetylene and air soldering kit. That indicates the use
of both ace and ox. Is there an ex tra knob on your handle for oxygen?
If so, your torch is not made to handle acetylene alone. Your
problem seems to be either wrong torch or wrong typ e of