notably the glue,and the poster the reactions as the paper and the print all are at a chemical reaction, and the wood back as used,
however there is a way as the poster as you want, is to take it to the nearest framing shop and they should save as the image, and also show you how to do so,
as you could have lost the poster you like,
Google Decoupage. I'm sure there is a lot out there about it possibly on You Tube. Craft stores are good places to get advice.
