Complex sentence: Several brands offer a black blade made by an extra firing or sintering via hot isostatic pressing (HIP), which improves the toughness of the blade, the main shortcoming of ceramic knife blades.
Split into simpler sentences: Several brands offer a black blade made by an extra firing or sintering via hot isostatic pressing (HIP). This process improves the toughness of the blade, the key limitation to using ceramics in knife blades.