I have a copper lamp that’s 30 years old. A couple of the Solder joints have disengaged on the lamp. Do I need to remove all the patina and oxidation layer on the copper before I re-solder?
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12Pictures, please. Answers profoundly depend on things that are not trivial to derive by Q/A series.– fraxinusCommented Aug 4 at 20:06
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1) I recommend that you get some scrap copper and practice soldering that before working on the lamp. 2) You only need to clean the copper where you want the solder to go. 3) Remove anything that could be damaged by heat before starting. Copper is very good at conducting heat.– Andrew MortonCommented Aug 5 at 18:49
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4 Answers
You want clean surfaces for electricity to pass though and for solder to bond to. Patina and oxidation could cause resistance in the circuit causing heat.
You sand old copper pipes to get nice shiny copper before soldering or else it leaks.
Solder like every other adhesive, wants clean surface to bond to well. It might stick, but staying struck is different. With electricity that might hurt/kill you. 30 years it might have polarized plugs, but having a ground is iffy for a lamp.
I imagine the joints are in the socket, if so replacing the socket might be easier than soldering.
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8OP mentioning "copper lamp" makes me feel that we're not talking about electricity here but structural solder joints between pieces of the lamp body made of copper. Yeah, we really need pictures.– TooTeaCommented Aug 5 at 15:55
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1@TooTea Quite possible. Quite sure I have a small old copper oil lamp around somewhere. Will depend where the joint is, but one that might leak should be done to higher standards.– crip659Commented Aug 5 at 16:47
I would clean the copper thoroughly before trying to solder it.
I use those green scouring pads (Scotchbrite) to clean copper, does not leave particles of sand around.
You will need to use a flux and a suitable solder. Remember there are different solders available - plumbing solder is lead-free (but that might depend which country you are in), leaded solder is still available and is easier to work - better "plastic" flow and slightly lower temperature.
Also there are different fluxes available, I have one that is very aggressive but will deal with some impurities while soldering. Needs cleaning off thoroughly after though as, like any flux, it will corrode the copper.
Depending on the flux used, oxide layer may or may not be a problem when soldering.
If you think that removing the patina is labourous or will degrade the look, try using more agressive flux - e.g. hydrochloric acid.
Cleaner is always better. Just scrape it with a knife to shiny surface. Electric solder contains its own flux; the lead is a hollow tube with rosin inside. So while you solder, it smells like pine trees.
