If I remember correctly all film stock will degrade with time fading or turning pink, and it’s worse with movies from a certain era onwards, which is why movies are stored underground away from moisture or light. So they can be preserved for long time but not forever.
True, but even though the negatives for the OT were stored properly , they still were in bad shape circa 1994, due to the fact that they were printed on quick fade film stock.
Secrethistoryofstarwars.com says these types of film negatives need to be corrected every 5 years to compensate for fading. I guess I don’t quite understand how you compensate for the fading. I don’t know enough about film preservation to fully understand how this works, it seems like people are saying sections of the negative are original, they’ve just been color corrected and cleaned up with chemicals. But the article also says some sections were so badly faded, they were unusable. When they were color corrected, does that somehow change the damaged film back to looking normal, and then it’s stable for another 5 years, or do you have to create a new piece of film?
Edit: I re-read the secret history article and got my answer. Some sections of the negative were unusable so they were replaced with copies of sections of the interpositives. From what I can tell, the faded sections were replaced with new interpositives color timed using the separation masters. So it sounds like large portions of the original negative are in fact lost and replaced with new interpositives, even the sections that have no cgi alterations.