Ceramic reflectors can be glazed both inside the cavity and the out surface using a highly reflective glaze that seals the ceramic against ingress of cooling fluids that may alter the refractive index, introduce impurities and reduce reflectance and efficiencies. Glaze can also act as a filter and our yellow glazed reflectors have been used successfully in certain applications. The visible yellow color is complementary to the spectral colors violet and indigo and effectively absorbs these wavelengths up to around 450 nm.