...or indeed any proprietary silver cleaning product. Personally, I find the cream-based ones are those that work best (use the sponge supplied or a soft toothbrush to work the cream into the piece, then rinse and brush off if the piece is intricately worked), and "miracle dips" those that work worst, with wadding and impregnated gloves somewhere in between. YMMV.

However, the electrochemical method described by Jen is by far the most scientifically satisfying - IF you can get the silver in contact with the aluminium. With a silver-topped (or gold-backed) ring, it may be difficult.

No, but you could try putting some washing soda crystals in sulphuric acid, and see what happens (from a safe distance).

Washing soda is also known as sodium carbonate (not bicarbonate); it produces a mildly alkaline environment which softens water and removes some stains directly. If you cannot find it, you can heat some sodium bicarbonate (commonly known as baking soda) to about 200 °C in the oven, and it will decompose into water, CO2 and sodium carbonate. Water will evaporate at 200 °C and CO2 is a gas, so the powder you'll get after the heating is effectively pure carbonate.

I don't think there's too much left of it by now, but I'd leave it in. It will add some colour to the fireworks.

(Actually, if you want to entertain your grandchildren with some real but harmless "fireworks", take a big bottle of Diet Coke or other strongly carbonated drink, pour in a packet or so of Mentos, and move away)

I will try all these helpful hints as soon as  I have finished digging the bunker in my yard.
It is wonderful  to have such good helpful  friends.... 

      "Here´s to you kid."

Thanks for sharing the tips.