i have a suggestion if anyone's willin to take it up:
the whole idea of heating a metal to "revive" it is a common industrial process known as annealing. except that for metals u'll have to heat it up to temperatures of about 300-400 degrees, usually higher. and preferably in vacuum, or a non-corrosive environment. if im not wrong, vinegar is acidic and it's effectively corroding the protective coat on the strings so while it may appear to have an added effect on revivin the string, it will eventually damage the string after repeated boilings.
anyway, since such high temperatures are hard to achieve at home; u could try boiling the strings for a much longer time. on the order of maybe an hour or two, or more if this has been the tried and failed method. this should achieve the same effect as having high temperatures. then u'll need to slowly cool the strings, so reduce the flame on the stove bit by bit, until eventually the bubbling subsisdes, then until the water cools naturally at room temperature. then only take the strings out of the water. it is essential that the cooling process is slow, pehraps take an hour or more.
it may or may not work.. but if anyone's got time on his hands and is game to try, share the results at the end!
