If the water-cooled or oil-quenched specimens were found to have an inadequate toughness for a specific engineering application, how could the toughness of these specimens be improved? The heat-treatment could be repeated, with better stirring of the quenching medium during the quenching operation. The material could be reheated to a temperature between 200C and 650C and held at the chosen temperature for an hour or so. The material could be reheated to a temperature between 650C and 950C and held at the chosen temperature for an hour or so. The material could be reheated to a temperature of 950C and held at this temperature for an hour before repeating the quenching operation. It is necessary to wait for some time after quenching to allow for the diffusion of carbon within the material. This will allow the toughness of the material to slowly recover.