No matter how beautiful the art on your poster, a fold mark or any type of wrinkle can ruin its appearance. While prevention is the best solution for keeping posters in good shape, sometimes creasing the delicate paper is unavoidable when a poster is moved or put into storage. Before you give up your wrinkled poster as a lost cause, the application of some heat and pressure may restore it.
Cover a flat board with parchment paper. The board should be larger than your poster.
Unfold your poster carefully and lay it as flat as possible on top of the parchment paper. Cover the poster entirely with another layer of parchment, making sure the poster remains flat beneath the parchment.
Hold the parchment in place with one hand. Turn on a hair dryer set on low heat. Aim from directly above so that you don't blow away the paper, holding the dryer 12 to 18 inches from the parchment paper.
Move the hair drier back and forth, slowly, continuously, directing hot air at the problem spots until the parchment becomes very warm, but not too hot to touch.
Lay another large board on top to sandwich the poster in between the boards. Clamp the boards tightly in the corners, or add heavy weights on top of the boards. Set the assembly aside and leave your poster there for a week to remove the creases.
Remove the clamps or weights, then carefully remove the board. Pull off the parchment paper. Any fold lines, wrinkles or creases should be fixed and your poster will be flat. Discoloration or loss of color in a fold line needs to be repaired by a professional restorer.