Three methods of measuring the normal spectral, total normal and total hemispherical emissivity of opaque solid materials are described. Spectral emissivity measurements are performed at approximately ambient temperature and encompass the wavelength interval .4 to 25 microns. Total hemispherical emissivity measurements cover the temperature range 0 C to 600 C. Results of the emissivity measurements, of various materials, as performed with each of the systems, are presented. (Author).

The emissometer is an extension of the multiproperty apparatus which is a powerful and unique tool for simultaneously measuring ten thermophysical properties on the same sample of an electrically-conducting solid and of studying its behavior under various environmental conditions. The apparatus features rapid time-to-temperature and data acquisition under minicomputer control yielding state-of-the-art accuracy. Performance evaluation tests of the emissometer are presented. These tests deal with veiling glare, blackbody cavity quality, and temperature distribution in the heating tube and sample. In addition spectral emissivity measurements to at least 10 micrometers have been made on tantalum (reference material), SiC, Si3N4, graphite and carbon-carbon composites from 1500 to 2400 K or their respective degradation temperatures. The new data on the ceramics provides some understanding on their high temperature behavior including the effect of fabrication process and impurities.