cockling photgraph

[sisters]

yes the age old problem! we have mounted an expensive signed photo Glass size 48" x 25", which has come back 3 weeks later the photo has cockled , We have t hinged at top on to backing board, customer does not want it dry or cold mounted, It is hanging on a ' cold ' wall not damp, I am thinking to pack it out with some foamcore , prehaps some foil backed corri core and prehaps layer of melinex to help prevent it from happening again, any suggestions????

[prospero]

You don't mention the type of paper, but typically big photos just plain do that no matter how carefully you hinge them. I'm betting it's been rolled up at one point.
If it's a glossy, it will show up any minor deviation from the flat.