I store mine in those page-protector-like things in a zippered notebook. I usually stand the notebook up, so the negatives would be sort of
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I was just wondering as I was rearranging my WorkBoxes filled with pages of negatives and slides and recalled reading somewhere about how people stored their stuff vertically, which in this case is bad as I don't have that kind of space, they work a lot better horizontally.
I store them horizontally in pergamon sleeves (this sleeves let them 'breathe'),in a binder. And is there any difference if they are in the vertical or horizontal position???
I have all mine in neg sheet page holder thingies (can't remember the name sorry). Some laying flat in drawers, some standing in binders and a couple of pages tossed haphazardly in my locker.
Now that I think about it, I am Loose Gravel's answer as the binders are facing magnetic north while under a pyramid.
I'd almost forgotten, but one of my student yearbook photographers back in the 1970's used an empty plastic ice cream container for storage--at least until I "suggested" otherwise. He didn't bother to cut the negatives into strips, just left them coiled up in the container. I'm not sure what he thought the negative-holders we had available were to be used for.