it was recommended to me that a 50/50 mixture of Sparex and hydrogen peroxide (over-the-counter brand) be used as a pickle for nickle silver.
There are various forms of “over the counter” hydrogen peroxide.
One can be found in the “Antiseptic” section of the drug store,
the other will be found where ever the hair dye products are.
The hair product Hydrogen Peroxide is between 10% and 40% . I
think the antiseptic kind is about 4% . I am still wondering
which to use . . .