This spell tempers an item, instantly adding hardness and hit points. The item must weigh no more than five pounds per caster level of the caster. For every 4 caster levels (up to 20 caster levels), increase the item's hardness by 1 and hit points by 2. The bonuses granted by tempering do not stack, but can be used to overlap on an item already tempered or hardened. This tempering bonus stacks with the hardness enhancement granted by the magical enhancement from enchanting weapons and armor. Items which are broken, taken apart, reforged, or otherwise reformed lose this bonus.