Sue, To bring up fine silver from sterling sheet… Heat the sheet
gently as you would to anneal it. Quench it in water. Then pickle it.
Repeat this several times … ie heat, quench and pickle, heat,
quench and pickle.
What you are actually doing turning the copper into copper oxide by
heating the sterling silver. The pickling removes the copper oxide
and leaves fine silver behind. As you repeat the process, more copper
oxide is removed and the fine silver at the surface becomes purer. You
can tell the process is working because the surface of the silver
begins to turn white.
Do not use a brass brush after pickling as this will remove the thin
layer of fine silver.