A method of measuring spectral emissivity of materials is provided. The method comprises placing material in a controlled chamber and exposing the material to an energy source to heat the material. At least one multi-wavelength pyrometer measures the spectral emissivity of the material produced by heating by the energy source, wherein the multi-wavelength pyrometer is positioned at a distal end of a tube extending from the chamber, wherein the tube provides a sacrificial surface for vapor condensation to prevent the vapor condensation from obscuring a view port used by the pyrometer.