Tempered glasses are being used widely as safety glasses since they break into round pieces of fragments at their rupture when their rupture strength increases, however from the viewpoints of resource saving and energy saving, it is desired to reduce the thickness of tempered glasses. For thinning them, the heat transfer from the cooling media is an important factor. In this article, regarding mineral oil, molten inorganic salt and the mixture of mineral oils which are considered as the cooling media for the manufacturing method of thin tempered glasses, the effects of heat flux, heat transfer coefficient, liquid temperature, etc. thereon have been studied experimentally. Part of the information obtained is as follows; concerning silicon oil, no clear burn-out point has been able to find. In measuring the heat fluxes of compressor oils with different coefficients of kinematic viscosity (or density, heat transfer coefficient and specific heat), the heat fluxes at the burn-out point have become smaller and the temperature at the burn-out point has become higher as the coefficient of kinematic viscosity has become bigger (density; bigger, and heat transfer coefficient as well as specific heat; smaller). 20 refs., 8 figs., 1 tab.