Abstract: The spectrally selective solar surfaces have been produced after heating the austenitic stainless steel AISI 321 at a firing temperature of 843.degree. K. and for firing times ranging from 10 to 20 minutes. The heating was carried out in a constant temperature oven under normal atmospheric conditions. The optimum values of solar absorptance .alpha..sub.s and near-normal emittance .epsilon..sub.s were found to be .alpha..sub.s =0.92+0.02, .epsilon..sub.s =0.22.+-.0.02 respectively. The corresponding values for the unheated steel were 0.50.+-.0.02 and 0.22.+-.0.22. Severe temperature treatments like quenching in liquid nitrogen at 77.degree. K. produced no adverse visible affect on the quality of the selective surfaces. It shows that the thermal coatings so produced are very tough and durable. The value of solar absorptance and near-normal thermal emittance remained unchanged after quenching in liquod nitrogen.