Quoted from MeesterPieter:
just thinking aloud here but maybe the ironing doesnt only harden the clear enough to not crack up again but may it also make the inking better stick to the playfield? if so this could also be used as a preventive measure in a new game with playfield susceptible to pooling and chipping?
I -strongly- advise against this.
I had some art lifting under a post on Wonka CE - it was otherwise perfect (no pooling etc) and I decided to iron it down as a "pre-emptive" fix.
The first time I did it, it worked. The second time, I overheated it and the clear lifted and cracked.
It's fortunately not in a gameplay area and I bought myself a playfield anyway because we play the everloving crap out of that game, so I'm gruntled.
Let my mistake inform others: never fix what isn't broken, beware the iron heat, only iron if you're pooled and need to do it to arrest damage.