Once in a while you come across a film which has been stored for many years in vertical position, and can only be rewound on a set of bench rewinds and not on the projector. I was wondering if the film was stored horizontally, whether it eventually cures the problem?

Robert,

I have always thought the "saggy" film was due to vinegar syndrome affecting the film and making it too twisty to rewind tightly on the projector. I have not heard vertical storage being another cause...interesting question though, it would be interesting to hear from those collectors who store films vertically. My films all lie horizontally.

Some of my 16mm and 8mm films I store horizontal but the rest of those and all my super 8 films I store vertical. I never rewind super 8 on a projector. I always rewind on the bench with a little tension so the films are wound tight and I tape them with paper tape. I do rewind 8mm on my Bolex M8 but this is done by hand with a hand crank. The 16mm gets rewound on the BELL & HOWELL (Eiki) slot load. It winds the films pretty tight. None of them have ever sagged.

Its generally considered that vertical storage of 16mm features allows too much weight on the bottom of the film. Whether this affects their eventual projection I don't know..

I keep my Super 8 films vertical and 16mm films horizontal, and I totally agree with Bill that a tensioned hand rewind of all films is the best way to go.

i did read on here some time ago that 16mm films are best stored horizontally. Larger reels especially can cause sag if stored vertically for long periods due to the weight on the bottom.
I would assume if films are bench rewound, as ours is as well, that this would help to avoid this problem.

Today I was lookin at some short videos of a film historian in the US, named Eric Grayson; surprised to find he stores is 16mm and 35mm vertical.