"Silver soldering" seems to use a much higher melting point solder than the usual electronic mix but looking around for some solder, lots of people seem to be offering solder with silver added to lower the melting point
Just one thing I do. I find that this modern solder is sometmes reluctant to flow out despite coating things with flux. Where you "tin" the parts first and coat them with solder I find it helps if you melt the solder on part then take the flame away and use a bit of wood coated with flux to brush the solder over the area to be coated while it is still molten. It will flow out and creat an even thin coating. Doing this on both bits to be soldered together guarranttees a good bond when you put the two parts together and heat them.
Adrian,
Modern solders seem to contain all manner of stuff to avoid or reduce the lead content. Silver soldering in the real sense is almost brazing and required considerably more heat than lead solder. You need a brazing torch or at the very least a bunsen burner.