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You've hit the nail on the head. Poor technique/equipment when winding film is the most common source of cinch type scratches. Constant tension and slow acceleration are needed to wind a tight even roll without the film convolutions rubbing on each other, letting dirt particles cause cinches. Good idea to keep the film from touching dirty surfaces too.

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

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I hate to say it, but 3-D was a major contributor to the problem. The idea of putting 6,000 feet of film on a single reel and trying to run with a longer set of reel arms and a slip clutch was outside of any reasonable engineering design, but projectionists got away with it, and found they had to do fewer changeovers. The rest is history.

There were attempts to increase the diameter of the reel, attempts at beefing up the spindle (which sometimes broke from the weight and mis-handling) with an adapter, and attempts to reduce the torque problems at startup with more expensive floating hub reels, but the bottom line was and is still the same. The discrepancy in diameters of film from start to finish is too great for a simple slip clutch to handle properly.

The huge hubs, dancer arms on platters, and feedback systems are such an improvement that, in my opinion, old style large (over two reel) take-up reel systems and crude rewind benches should be banned. Only cost keeps there from being an interactive tensioner on large take-up reels and a tensioner on benches.

Joe and John are correct that "on-off" rewind benches will create cinch marks, but the cinch problem would be greatly reduced if the loose wind of the take-up reels was corrected at the source.

Excuse the grumble, but I damaged too much film early in my career from big reels, dirt, slip clutches and rewind benches powered by washer motors. Having to deal with acetate and fox hole sprockets didn't help. On one set of projectors I couldn't get sufficient tension on a full reel unless the clutch was set tight enough to proud the perfs on the head of the winding film. This forced me into recognizing the problem and using single reels or only putting two reels on a big reel. I did eventually get better at hand cranking a film up to speed and matching the motor speed, but sometimes I could still feel the cinching as I started to rewind, especially on damaged film.

If I'd had more of a brain back then I would have increased the length of the head leader by a hundred feet or more to minimize the damage. But back then I was too trusting that people designing machinery knew what they were doing and there was little a projectionist could do to improve things.