A very good question! I am afraid I am no arcane scholar, so I will simply have to be vague in my answer, but in our home world we determined that if one weapon is enchanted one way, and then we introduce another enchantment on top of that, we soon had explosions and foul magic and all sorts of distractions that are not generally preferable in battle. This formula does have arcane elements to it - most notably, a magical rune that is carved against the back of the paper.