Once silver has cracked, it is extremely difficult if not impossible
to solder it back together. The area where it cracked has become not
only brittle and ragged but probably contaminated. The only way I
know to repair it is to pass a saw blade through the crack to clean
and smooth the surfaces of both sides. Then fill the cut with sheet
metal that is forced in and then solder. The sheet can then be
filed smooth on both sides.
This often happens to my students when they are doing heavy overlay
because they have not yet learned torch control. If it is a simple
surface, like on a bracelet, the above process works quite well. ,
On a box with many small fractures.....?
Sorry but cheers anyway from Don at The Charles Belle Studio in SOFL
where simple elegance IS fine jewelry! @coralnut2