You can do without solder, but you’ll change (because you melt!)
the surface into something like the moon’s landscape…it is
nice, though. I sometimes make this kind of rough-looking
jewelry. I don’t know how it works with hydrozone apparatus, but
that jeweler might have meant this: nowadays one can use
laser-soldering machines for a lot of purposes, especially for
soldering delicate or antique pieces or pieces with delicate
stones, because the piece doesn’t get hot except the very
soldering spot. >