The above is a bit alarmist.(posted 9006 days ago)Are they Cellulose Nitrate, which is unstable and potentially a fire risk, or Cellulose Acetate, (Safety Film) which is much more durable. If you can determine what sort of film base you are dealing with, then it will make a big difference to the sort of treatment they need. Whatever material they are, your first step should be to scan them into digital images, in colour, even though they're black and white. That way, even if the negatives are ruined by attempted restoration, the images will survive, and it's amazing how much can be retrieved on the computer. The reason I advise scanning in colour, is that stains can be filtered out more easily, and colour scans hold much more information than 8 bit black and white.