Mix water and ammonia in equal parts, enough to immerse the object in the mixture. Add the ammonia solution to the bowl or container. Allow it to sit for 30 minutes.
Remove the item from the solution. Gently scrub the object with the soft-bristle brush to remove tarnish. Repeat in 30-minute intervals until the tarnish is gone. Rinse and dry the piece completely.
Apply nickel polish to the object, and buff it until you achieve a sheen you desire. Wipe excess polish from the item.