I used to work for 60 minute photo processors in the 1980s. The main one used Copal machines, and the C-41 processor used friction rollers for transport (this allowed paralell paths, so 2 rolls of film at a time). Occasionally, something jammed up, and everyhting just stoppped transporting (usually the machine just jumpeed up and doqwn trying to continue transporting). Most employees would just shut off the power to the machine, and call the technician, and by the time he got there, most of the contents were largely lost. I did this a few times when this ocurred - I shut off the machine, turned off the room lights and dropped shades in the window. Then locked the front door (all in less than 3 minutes) if I could (i.e., no customers present). I then popped open the metal lids and started pulling the drive sections (also containing the film mid-transoport) in the various solutions (dev, stop, bleach, fix). In subdued light I first finished any development by dipping and putting the lid back on. Then I finished the other operations, including bringing the completed developed materials through the rest fo the process. Timing was always very approximate at best. I usually saved most of the film, though some of the materials in the first part of the process ended up poloarized, plus in some areas there was folding, scratching, etc. I then printed the negs, charged $0 for the process and gave the customers a replacement roll (this last item and the $0 was our only warrantty). Most of the customers were happy I saved their pictures, and many that ended up with posterized images got a real kick out of them (I explained that sometimes people actually do thi on purpose...). It was pretty rare surprisingly that images were completely black.
