Although there are always chemicals in fluxes, liquid or paste, that
can produce fumes that are not good for us, I prefer to use a paste
flux that, at least, does not contain fluoride. I use Dandix Flux
instead of Handy Flux, for this reason. Always have and never even
used a liquid flux for anything.
Cupronil is a non toxic liquid flux that prevent fire scale from
forming on sterling silver during the solder process. It may be used
as a flux for solder joints.
Cupronil does what it promises to do and that is to prevent fire
scale. The use of Cupronil to prevent fire scale when soldering will
save considerable amount of time in polishing your project.
If you vacuum cast sterling silver check out my paper on Orchids
"Tips FromThe Jewelers Bench" on preventing fire scale when casting.
It is a very simple process that will prevent fire scale on cast