of aluminum oxide. Tin The first tin-coated glass mirrors were produced by applying a tin-mercury amalgam to the glass and heating the piece to evaporate the mercury. Gold The "silvering" on infrared instruments is usually gold. It has the best reflectivity in the infrared spectrum, and has high resistance to oxidation and corrosion. Conversely, a thin gold coating is used to create optical filters which block infrared (by mirroring it back towards the source) while passing visible light. See also Dielectric mirror List of telescope parts and construction Optical coating Mercury glass Mercury silvering Metallizing References External links Tions.net, Diy mirror / mirroring / silvering Chemical processes Mirrors Silver