"David W.E. Roberts" wrote in
:

Heating the pipe near the joint, heating the joint, heating away from
the joint for a slower raise in temperature.
There seemed to be about a microsecond between no solder and the
'spifzz' as the ring of solder spat out of the yorkshire joint.

Usually ended up tinning the end of the copper pipe with solder and
then easing gently in.
Used a load of solder but usually worked in the end.

You may have missed one essential - apologies if you haven't - and that is
to make sure the end of the run is open to the air.

If there's a tap or valve, make sure it's open, if not the expanding air
due to heat will blow out the joint.

You can also tlerate some water not too close if there is no chance for a
pressure build up

HTH

mike r