Soldering Help Needed

[ps_bond]

Right, I've just gone and tried:

20x20mm square of 0.8mm copper, borax, hard solder chip (full thickness, not rolled down at all) Nimrod T75 butane torch - slow, but got there eventually. Solder melted & flowed, although not all that far - I suspect the flux was probably used up by that time.
40x40mm square of 0.8mm copper, borax, hard solder chip, Nimrod T75 + another butane torch, copper boxed in with ceramic block to retain heat - gave up after 5 mins. Flux was black, but there was no way the piece was ever going to hit solder flow temperature.

Refluxed, hit with the Smith Little Torch (#6 tip) - 5-10s for the solder to flow.

Butane torches are great little things for small jobs, but they don't really have the BTUs to get reliable joints in larger pieces. If you don't want to jump up to something like a Sievert, then one of these would probably do well - http://www.diy.com/hand-tools/tp2062.../196618_BQ.prd Usually I'd suggest some of the Bernzomatic range, but B&Q don't seem to do them any more.

[Patstone]

I have a diy torch like that. When I bought my house it had small radiators in so I bought a torch like that to enable me to add some bigger radiators. It had been out in the garage for years and a couple of years ago I re-found it, so I was able to make use of it if I got a job that was too big for my normal torch. The only problem with them is they roar and if you are soldering in a spare bedroom complete with expensive carpet its a bit scary.

[susieq]

Right, I've just gone and tried:

20x20mm square of 0.8mm copper, borax, hard solder chip (full thickness, not rolled down at all) Nimrod T75 butane torch - slow, but got there eventually. Solder melted & flowed, although not all that far - I suspect the flux was probably used up by that time.
40x40mm square of 0.8mm copper, borax, hard solder chip, Nimrod T75 + another butane torch, copper boxed in with ceramic block to retain heat - gave up after 5 mins. Flux was black, but there was no way the piece was ever going to hit solder flow temperature.

Refluxed, hit with the Smith Little Torch (#6 tip) - 5-10s for the solder to flow.

Thanks Peter - that's a very interesting and useful experiment.

[ps_bond]

I tried to limit the variables, but I know there are plenty... Hardly pure scientific method