I Broke My German Tanker Ashtray

[ithacaartist]

The original joining appears to have been done with silver brazing alloy (silver solder) or perhaps lead/tin solder. These are both adhesive processes that use way less heat than "brazing", which uses bronze alloy filler rod. Soft solder(lead/tin) tends to be the least structural, but it uses the least heat to melt the filler and adhere it to the work. Any heat applied to any area will result in the entire piece heating up, because brass and copper parts are very conductive. A clean, tight-fitting joint is very important whatever the process.
JBWeld is great stuff for the right project, but on metal, only a superficial adhesive bond is accomplished, susceptible to falling apart if, say, you dropped the completed work on the floor afterwards. If you choose to reattach the outside shells with a metalurgical process, be certain to remove ALL traces of old JBWeld, as it will affect the quality of the finished joint.
I figure the person who initially created this ashtray wrecked the patina on it to begin with, via his own heating of the piece, but if you have concerns about the appearance of the patina, then I agree with Ollie--drill and tap. Ollie, how is adding a set of new fasteners and holes in the components any better aesthetically than re-soldering? Heat would wreck the paint? Were the projectiles originally painted? If so, the FIRST guy wrecked the patina when he soldered them to the central brass, and then touched them up/repainted.

[Olle]

Originally Posted by ithacaartist

Ollie, how is adding a set of new fasteners and holes in the components any better aesthetically than re-soldering? Heat would wreck the paint?

Yeah, I'm afraid that any method using heat will damage the paint and the old patina around the joints. I would use screws from the inside, that way you won't see much of them unless you peek inside. If you still want to use solder, use a large iron heated with a torch (like they used in the old time radiator shops), it will apply a lot of heat quickly. Once the solder melts, cool it down with a wet rag to prevent the heat from spreading. An electric soldering iron takes longer so it will spread the heat further out from the joint, and a torch is a no-no in my opinion.