I bet you are having trouble with the solder you are using. The ZD PRO FLUX will make his life easier. Also Zinc has a melting point about half that of copper...he should use propane and a torch. No problem soldering in the cold, but bending is an issue. He may consider fabricating inside until warmer weather. Radiuses should be watched. Rule of thumb:1 1/2 times the thickness of the material thickness.