Jack, >I always thought the main problem was to get a high enough temperature.
Agreed but it's also HOW you achieve that temperature that counts. For a large workpiece spending pre-heating the whole job to prevent heat being soaked away by surrounding cold metal before concentrating on the joint will help. >I have, sitting in my >garage, a gadget that I have only used a couple of times -- a sort of >cheap poor-man's torch they now sell in the US consisting of a small bottle >of mapp gas and a small bottle of oxygen. >How can I get a flame that is both hot and carbon rich? Can I use a flame >with oxygen added? With my oxy-acetylene rig it's a question of 1. Setting up a neautral welding flame with the correct pressures then 2. increasing the acetylene slightly so that the white central cone is increased to the point where it becomes slightly ragged 'acetylene haze' at the tip. You would get a similar effect by reducing the oxygen but the lower pressures might cause troublesome 'snap-outs'. I don't know how you would apply this to the torch you describe. > I assume 'mapp gas' is butane? Propane will give higher temperatures. These days I use a plumbers propane torch for all small to medium sized silver soldering. This is just a specialised 'Bunsen' burner with a handle - used by roofing specialists. plumbers etc. and available in large sizes to give a high output flame. The air inlets can be adjusted to give a slightly carburising flame i.e. don't go so far as yellow tips on the flame when heating power is much reduced. Prior to that it was a gas-and-air torch using mains gas and a foot bellows replaced by an electric blower when I could afford it. That arrangement would silver solder any gnomon I've ever made. During national service near Baghdad back in the 50s I loved to watch the local Arab jewellers silver soldering quite large bracelets etc. with nothing more than a tin can of crude oil with a smokey flame from a burning rag and a mouth blowpipe. Up to that point I'd always thought specialised equipment was essential. Tony Moss
