Take them to a frame shop and have them dry mounted,,,,,,,,,it is a process where there is a film applied to the back of the poster and to a material called foamcore,,,then it is placed in a heat press and the posterwill come back to you flat,,,,if it has cracked,,,you will still see the cracks but it will be flat! If you would like to try it yourself,,,,use spray adhesive,,,,but don't use cardboard,,,the acid in it will cause brown spots on the posters,,,, The foamcore is acid free! Get a helping hand and start on one end and gently ease the poster down,,,the spray adhesive is unforgiving,,if you screw up and it sticks in the wrong spot,,,it ain't gonna release,,,,your screwed! Been there,,,done that! HRP
Dry mount will work, but you'll never be able to get the print off again, and it dents really easy. Plus it looks so... Office Depot. I mean, if you just want something to mount a ****py poster to , go for it, but if it's a good poster that you want to display you need to do it up right. What I would do is get a couple pieces of clean cardboard and sandwich the prints, and weight the top down with a couple of books. Slide it under your bed for a couple days so the dog won't step on it, and then you can take the to the framers shop nice and flat. The framer will use little corner hangers to mount it uner a matte, and that way you don't destroy the print.
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