Fixing warped foam core - help!

[stone-cold-lead]

Got a couple of small sheets of foam core that have slightly warped thanks to my poor storage and I wondered if anyone has a tried and true method for safely flattening them out again? Of course I tried leaving heavy books on them but that didn't really do much in the short term. I have wondered about applying a bit of heat with either a hair dryer or the iron but thought I'd ash here before trying anything drastic.

[Jerekin]

Had the same problem. I had the feeling once the foamcore was bent the inner structure was somehow squished and compressed at the inner side of the bend. Your only chance is to squish the other side aswell while pulling the compressed side apart until it comes to a balance again. (Basically overbend it in the other direction.) Be Careful though. If you overdo it you can damage the inner structure.
I did it with floor and wallpaper insulation in 3mm and 6mm.

Heat might help but I have no experience with it.

Cheers, Jere

[nic-e]

bend them in the other direction, Bu do so gnetly over your knee, Moving it from side to side while applying tiny bits of pressure in order to slowly work the foam back the other way.

Equally storing it the same way you were storing it but the other way up can do it if it was a humidity/support issue.