The total (0.6–40 μm) hemispherical emissivity of sintered silicon carbide samples was measured in different conditions of pressure and temperature, from high vacuum to atmospheric pressure in air and up to 1850 K using a direct method. Emissivity data are correlated to the presence of different thicknesses of the silica layer and material characterization using scanning electron microscopy, ellipsometry and 3D profilometry was carried out to complete the interpretation of the emissivity evolution with temperature and pressure according also to surface roughness.