I have never seen anyone support copper water lines like this before.
What would you have to say about this.
What you see is a copper water line,
The cross copper is a scrap piece jammed between the joists
the two pipe are soldered together to stabilize.
Over all its discolored, looks corroded, unknown if the pipe is damaged from the solder process.
It’s common here. No problem, the sweating doesn’t hurt the pipe.
I was glad they at lease did copper to copper.
Actually John, its an old timers way of really supporting the pipe well. That extra copper pipe bracing costs much more than a copper clamp also. A real plumber probably installed it.
Looking around Google it is from the flux.
My take is it must be because there is excess left over due to there not being any suction of it into a joint.
That would be a reasonable foreign material causing the corrosion and coloration. Thanks Bob
Thanks Cameron
Guess I’m not that old. Thanks Dale
I bet you’re right Bob, I wonder if the flux residue holds moisture too
Well a real plumber would have wiped the flux off after sweating the pipe. Maybe it was a descendant of a real plumber;-)
LOL, good one. Four generations later you’ve got garden hoses spliced into the system held up with coat hangers. 
In order to solder copper pipes Here are some basic steps:
1 Use emery cloth to clean inside/outside of copper tubing.
2 Apply flux to pipe and fitting with acid brush.
3 Heat fitting with propane torch until flux bubbles.
4 Apply solder to fill joint; wipe off excess solder with rag.
5 For an easier way to sweat joints, use pre-soldered fittings, which require the application of heat only.
6 Slide nut onto tubing, then tighten flared connection using two wrenches.
7 For a no-solder compression fitting, slide brass ferrule onto pipe, add nut and tighten fitting to join two pipes together.
8 Copper fittings lined with neoprene gaskets permit pipe connections without special tools, wrenches or a propane torch.
Your no plumber until you can control the temp of the torch and the copper pipe and make the solder travel up a vertical pipe for 18 inches. Yes that is a test and OKIE test;-)
Most new plumbers don’t even know how to solder copper never seen any all they use is PEX