The problem with deoxidised silver is that obviously they have
been formed in an inert atmosphere, probably they were heated using argon as a shield. But once they are heated again the firestain returns. I have tried mechanically removing firestain with abrasives, but this tends to remove detail as well
I believe deoxidized silver is a special .925 alloy that resists
cupric oxides. I use it exclusively for casting and experience
no firescale even after repeated solderings. It casts bright and
reduces porosity also. The alloy I use comes from PMR in New
York, I believe they hold the patent for the alloy.
Thanks for the info on deplating.