As plain ol' table salt is the cheapest, I don't know why you'd want to use anything else. Besides, all it's doing is stripping the hard water deposits off the the gold and flushing it all away. There isn't any residual effect that I know of. Although... there have been folks that claim there are other substances that can be used if, for example, high blood pressure is a concern, Potassium Chloride can be used... but it is more expensive.