I was watching a Japanese craftsman making copper tea kettles the really old way. He soldered the spout and top ring very carefully. He did an excellent looking job,but where He touched the rod to the kettle He had a slight drip. When He went to clean the kettle up He just took what looked like a common tooth brush sized brass brush and it removed the solder and did not seem to harm the kettle. I cannot try this idea out right now, I hope this helps Someone out.