The radiative properties of industrial glasses depend on temperature, glass composition, type & content of colouring ions, water content & redox state. There is a lack of reliable data on these radiative properties, a unique high-temperature optical test facility was built for the determination of spectral absorption in the wave-length range of 0.7-9um of glass at temperatures up to 1450 deg C. Many of the systematic errors occurring in existing measurement methods are eliminated by the special features of this facility, which include control of the atmosphere above the melt & the redox state of the glass. This paper discusses the principle of operation based on the measurement of spectral emissivity or the ratio of spectral emissivities, the different measurement procedures, & the preliminary results obtained on clear float glass at 800, 1000, & 1200 deg C.
