A method of quenching a metal object comprising: (a) providing a reservoir of liquid coolant containing gas that has been dissolved therein; and (b) immersing the metal object in the reservoir to quench the metal. The gas is selected from the group consisting of nitrogen and carbon dioxide and is preferably carbon dioxide. The gas is preferably maintained within the range of 0.001 to 0.2 standard cubic feet of gas per gallon of coolant. The liquid coolant is preferably water. In a preferred embodiment, the reservoir of liquid coolant is open to ambient pressure and temperature.