I came here tonight with exactly the same question. I have some rolled posters and some folded. Storing them flat would be ideal as I have already found out that unfolding and folding causes stress to already old posters (and I am learning how to correct fold). My ex-Mother-in-Law was great for storing things in plastic bins. I don't suppose anyone has come across any poster size (or larger) plastic bins with lid that would nicely fit under a bed or the like? I have done some basic searches but no luck.
Thanks,
Matthew
Matthew, you're looking for a storage tub large enough to store your posters flat and unfolded/unrolled, right?
So it would have to be a tub that was approx 30x42x6 inches high (for under bed storage).
I did a look last night and could find nothing in anything close to those dimensions. I found a couple that were 30 inches long but only 18 or 20 inches wide.
I recall back in the day, my folks had these 2 huge under the bed storage containers. They were made of metal (maybe thin steel or aluminum) with a hinged lid. My guess is that they were about 60 inches long, 36 inches wide and about 5-6 inches deep. They had hinged lids. My mom could keep dresses or suits from my dad in these, totally unfolded.
I dont know if such a size critter is made anymore or not. Something like that could work - just line it with acid free tissue or acid free foam core.