Caustic Safeguard

You imbue a single object with an acidic protective ward. Any creature other than you that touches the object takes 1d6 points of acid damage per 2 caster levels (maximum 10d6; Reflex half).

Each time the spell discharges, the number of damage dice it deals is halved (rounded down); when the spell's damage dice reach 0, the spell ends. While casting this spell, you can touch up to one creature per 4 caster levels, which allows them to handle the warded object without triggering this spell.