Would you use two different fluxes for fine silver versus sterling silver?
I’ve been using “Gesswein Hard Soldering Flux” on fine silver, but
haven’t had a lot of luck. Sometimes the solder flows perfectly.
Twice the solder has stayed solid, just getting reddish-brown with
heating, sticking to the silver but not melting. Sometimes the flux
forms a white, crystalling coating on the silver.
I’ve just E-mailed Gesswein asking what is in this flux. It’s a
yellow liquid, if that tells you anything.