Enchant Item (3.5e Spell)

Enchant Item  turns the weapon, shield or armor into masterwork quality (if not already), then adds a +1 enchantment bonus for every three caster levels (+6 at 18th). This does not stack with other enchant item spells, but does stack with existing enchantments. Requires one hour of uninterrupted concentration and is permanent.

Disenchant Item:  the spell can act in reverse; instead, negating +1 enchantment for every four caster levels (-5 at 20th). Requires one minute of uninterrupted concentration, and lasts for one round per caster level. This can reduce the bonus to attack and damage below zero, such that a -2 weapon would subtract two from attack and damage rolls.