I found a herringbone silver necklace that had been submerged in a lake for years. It is badly tarnished, but it is silver as I have found the mark. I have tried the baking soda and aluminum foil a number of times, added salt, and even tried it using a ultrasonic cleaner, all to no avail, it is really tarnished bad. Anyone have any ideas other than the baking soda/foil method?