SRD:Erase

Erase removes writings of either magical or mundane nature from a scroll or from one or two pages of paper, parchment, or similar surfaces. With this spell, you can remove explosive runes, a glyph of warding, a sepia snake sigil, or an arcane mark, but not illusory script or a symbol spell. Nonmagical writing is automatically erased if you touch it and no one else is holding it. Otherwise, the chance of erasing nonmagical writing is 90%.

Magic writing must be touched to be erased, and you also must succeed on a caster level check (1d20 + caster level) against DC 15. (A natural 1 or 2 is always a failure on this check.) If you fail to erase explosive runes, a glyph of warding, or a sepia snake sigil, you accidentally activate that writing instead.