Pour 5 cups of water into a porcelain or glass dish.
Add 1/2 cup of nitric acid to the dish. Take care not to touch the solution or get it your skin or eyes because the acid can irritate your skin.
Place the gold jewelry into the solution. Allow it to soak for 12 hours.
Remove the jewelry from the solution with tongs. Rinse it thoroughly under cool water to remove any traces of the acid solution or dirt.
Dry the gold jewelry with a soft cloth.
Rub the silver jewelry gently with a stiff sponge meant for household scrubbing to remove the excess black coating, or silver sulfide. Be gentle because the jewelry might be fragile.
Place the silver in a commercial electrolysis cleaner. Add the amount of water and table salt specified by the manufacturer's instructions and plug in the cleaner. Most of the silver sulfide will come off the jewelry immediately after you plug it in.
Unplug the electrolysis cleaner and remove the silver jewelry when the jewelry is mostly free of tarnish. This could take as little as five minutes or as long as an hour, depending on the amount of tarnish. Rinse the jewelry under cool water to remove any traces of salt.
Squeeze a dab of toothpaste on an old toothbrush and gently brush the silver jewelry for two minutes to remove any loose dirt or silver sulfide. Rinse the jewelry thoroughly.
Dry the jewelry with a soft cloth and polish it with a silver polishing cloth.