User blog comment:FairyRaven/Fairy Tail Chapter 368: The Third Seal, Review and Commentary/@comment-82.20.156.238-20140128065458/@comment-7418318-20140129085627

Just what B214 said.

If Face is not affecting magic itself, but the mages, like corroding or blocking the magic container for example, it wouldn't have any effect on the bomb.

Or if that bomb was made/charged with the same curse magic that the Demons wield, it might also remain unaffected.