John Rumm wrote:
Lobster wrote:

People keep talking about heating for a few secs; well it's taking me
more like 1-1.5 minutes to get the joint up to enough temperature to
melt the solder. And all that time the flux is boiling/burning off I

That rings alarm bells...

mm, thought as much...

For a straight end feed fitting on 15mm pipe you should be able to
complete the whole joint in 30 secs - probably quicker.

think. But heated for less than that time, I push the solder against
the pipe and it *just* melts, forming a blob which immediately

I find if you keep playing the heat on the pipe, there is a maximum
delay of about 5 secs from the point at which the solder will just begin
to melt to when it will flow freely.

(unlike electronics solder, plumbing solder is deliberately formulated
to be non eutectic - so the transition from just molten to completely
liquid is spread over a wide ish temperature range - hence the need to
get the pipe hotter than just the threshold temperature at which the
solder begins to melt)

solidifies without running up the fitting, because the pipework/fitting
isn't hot enough. I'm using an ordinary butane cartridge blowlamp, with
a brass burner approx 15mm diameter and which seems to give out a good
blast of flame, and I'm using the hot part of the flame, not the blue
unburnt area. Does this make any sense?

Try another blowlamp[1]! It may be that yours is not focussed enough to
heat the metal quickly. Your description of the flux boiling off does
sound like it is the cause of your problems. Possibly try another flux
or solder. Those are the only things I can think of since given the
procedure you are carrying out, you ought to be making perfect joints
every time without any difficulty! (Not wishing to demoralise you, but
end feed fittings really are simple to use ;-)

Well, it does seem odd. I'm not normally totally cack-handed with
tasks like this! Just before I buy my new blowlamp - how far either
side of the joint should I be heating? I'm playing the flame over an
area about 1.5" either side of the fitting: could that be too much?

Thanks for the continued advice! TBH I'd have probably given up by now
but for the fact that I can't buy the fittings I need in Yorkshire
style (various 10mm - 15mm stuff).

David