the problem is probably related to 1) the little torch and its small
flame 2) the mass of the piece you're soldering to 3) soldering
technique and maybe 4) flux which has become too thick from
General soldering technique dictates that both pieces be brought up
close to soldering temperature before you actually begin the
I haven't used a little torch for some years, but I remember some
things. You probably want to be using the tip of the inner cone part
of the flame and not the softer part further out which tends to
oxidize the metal.
Personally, I think I'd partially melt the solder onto the heavier
piece, then hold the jump ring in tweezers in such a way as it is
heat-sinked (don't forget to file a flat on the jump ring where it
will contact the piece being soldered to) and gently press it into
the solder as the solder gets up to a high enough temperature to
complete its flow. You probably want to be directing the flame point
toward the heavier piece, just allowing enough heat to get to the
jump ring to allow it to come up to soldering temperature but not so
much that it melts...
Another point, don't overheat the solder. If necessary, hold your
solder pic against the solder as it comes up to melting temperature,
heat-sink it. If the solder overheats, it can develop an oxide
coating, and maybe even burn out some of the alloying metals.
If the flux is too thick, it will form a barrier, so if your flux is
old, it's possibly in need of some additional water to thin it out.
One more thing, if you've applied thick boric acid solution, you may
need to remove some from the area being soldered as it can form a
barrier just like overly thick flux.