Holding temperature and time are governed by the material and thickness respectively.[1][2] Regarding material thickness, longer holding times are needed for thicker materials.[4] This is to allow the material to reach a stable condition where the distribution and levels of stresses become more uniform and decrease.[3][6] The specified holding temperature is one that is at a high enough temperature to relieve high residual stress levels, yet is still below the lower transformation temperature.[4][2] In addition to the reduction of stress, high hold temperatures below the transformation temperature allow for microstructural transformations, therein reducing hardness and improving ductility.[6] Great care should be taken as to not heat the component above the lower transformation temperature, as detrimental metallurgical effects and impaired mechanical properties can result.[6] In addition, the holding temperature should not be greater than the original tempering temperature unless later mechanical testing is performed.