auflux...that green liquid
strictly speaking, auflux is marketed as a gold soldering flux, and is very liquid. I use it second nature, but from feedback on the forum, silver workers (rather than general jobbers, working in both gold and silver) find it unusual at first, comming from borax. You do flame it off, so it crystalises in a similar way, to hold the solder to the object, though it is a little more inclined to bubble up, or the pallion blow away from the flames force...but its soon got used to.
There are, as well, a few specific silver fluxes cooksons do, but i have never needed to try them, as a general gold/silver smith....but dedicated silver workers will have thier favorites