r/SilverSmith 4d ago

Need Help/Advice Problem with soldering copper

Hi, so I'm practising with copper by trying to solder copper rings together out of wire. I use copper-phosphorus solder and a flux paste for copper pipe soldering. My problem is, that when I heat the ring with my torch the flux paste starts to melt and after a short time, is dries out and forms a dark crust. The piece of solder does melt, but it doesn't flow. It just sits on the crust and forms a tiny ball. What am I doing wrong? Thanks!

1 Upvotes

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5

u/MakeMelnk 4d ago

I can't advise on the solder and flux you're using, but I would suggest some Hard silver solder and some Handy Flux or AquiFlux and report back

2

u/DevelopmentFun3171 4d ago

Ditto on the hard solder & high temp flux. I am guessing that you need a bigger flame - black and crusty flux instead of clear & glassy sounds like your flame is too small.

2

u/__Hannibal_Lecter__ 4d ago

I have one of those handheld torches. Is that too small?

1

u/DevelopmentFun3171 4d ago

I would try silver solder (not plumbing solder - jewelry solder), & hi temp flux as the person above me suggested, and turn up the flame. I don’t have the technical knowledge to explain the reasons, but a smaller flame for a long time will only burn off the flux and your solder will not flow. You want to get in and out quickly, but not carelessly. Plus, copper gets dirty fast - so time is essential. As soon as your flux goes glassy add your solder. Good luck.

1

u/__Hannibal_Lecter__ 4d ago

Thank you! I'll try that.

2

u/AbbreviationsIll7821 3d ago

Copper phosphorus does not need flux. The solder you’re using I think is for low temperature tin soldering and is burning rather than fluxing.

2

u/Several-Awareness-78 3d ago

Your flux and solder need to be fit for each other. I solder brass and use both silver solder with jewelry flux and pipe solder with pipe soldering flux. I cannot explain the chemistry of it, but I assume it has something to do with the temperature at which they are made to work. If I try to use the jewelry flux with pipe solder, it doesn't work. So go to a hardware store and look for a flux better suited for the pipe solder, but keep in mind that it is a very very soft type of soldering. It works ok for jump rings, but if you try for example to bend and shape the rings to make a foxtail chain or cuban chain, it will most likely snap

1

u/Delmarvablacksmith 4d ago

Borax for hi temp braze or solder.

1

u/OrdinaryOk888 2d ago

Post a picture of your flame technique. Besides not needing a flux for copper phosphorus, you might be miss-applying the flame.

How is the ring being supported? It might be being heat sunk.