ASTM E423 is an accurate method for determining the normal spectral emittance of electrically non-conducting materials at temperatures ranging from 1000 to 1800 K and wavelengths ranging from 1 to 35 m. This test method requires a specific specimen size and design, as well as a specific heating and viewing procedure.
This test requires a spectrophotometer. Optical alignment of the spectrophotometer is should be perfect to minimize differences in absorbance along the two paths of the instrument. Careful adjustment of the chopper timing is needed to reduce overlap of the reference and sample signals (cross-talk), and precautions to reduce stray radiation in the spectrophotometer are required to keep the zero line flat. With proper adjustment, the “100 % line” will be flat to within 3%.
