I have never used Prip's or Stop Ox, but use Cupronil. I manufacture
and distribute Cupronil.
It's makeup is slightly different from Prip's flux. Because of that
I believe it is a better flux. Cupronil has been on the market since
1974 and may be the original stop firescale flux. Stop Ox came along
many years after Cupronil.
Firescale is the scourge of all silversmiths and must be eliminated.
You must use an anti-firescale flux, no matter which one you choose.
Hope to meet many of you at the Orchid Dinner,