This paper discusses differences in the spectral reflectances of fire-protective coatings during their operating life. The testing technique and the results make it possible to reliably determine the properties and the suitability of the coating that is used.
V. G. Surin and E´ . V. Kuvaldin, "Nondestructive testing of the status of fire-protective coatings by a photometric method," J. Opt. Technol. 70, 684-686 (2003)