Hot water foam repair
Lightweight closed cell foams are vulnerable to crush conditions, where the force is great enough to squeeze out foam through holes in the bubbles, which tend to stay deflated. Uncovered, they are also very vulnerable to scratches. Foam that is bent but not broken may also have creases.
Boiling water appears to be able to partially re-expand this foam to its original pressurized shape, possibly by seeping into the slightly permeable cell structure and turning to vapor, then slowly drying out in a way that replaces the water with air. This trick is widely practiced among RC flyers, and is reported to work best on EPO.