Symbol . This describes the relative ability of the surface of a material to emit energy by radiation. For the glass industry, this term
normally refers to the “Far Infra-Red” energy band more commonly known as “Heat” or “Thermal” energy. Emissivity is the ratio of
energy emitted by a surface relative to the energy emitted by a blackbody radiator heated to the same temperature.
This value ia dimensionless as it describes a ratio between these two measurements quoted as a value between 0.00 and 1.00. A
true “Black Body“ radiator will have a value of 1 which means it will re-emit all the energy it absorbs and a perfect reflector would
have an emissivity of 0, absorbing nothing. The term “Low Emissivity” refers to surfaces with values close to 0, typically 0.02 to 0.2 in the