User blog comment:FairyRaven/Fairy Tail Chapter 331: Natsu's Strategy, Review and Commentary/@comment-3290324-20130517205151/@comment-1776824-20130518170405

Dragon scales repel all non-Dragon Slayer forms of Magic. So, unless it was the Gravity Dragon Slayer (or some other form of bullshit >_>), the endeavor would have been pointless. :<