Metallisation is performed using a physical vapour deposition process. Aluminium is the most common metal used for deposition, but other metals such as nickel or chromium are also used. The metal is heated and evaporated under vacuum. This condenses on the cold polymer film, which is unwound near the metal vapour source. This coating is much thinner than a metal foil could be made, in the range of 0.5 micrometres.
This coating will not fade or discolour over time. While oriented polypropylene and PET are the most common films used for metallisation, nylon, polyethylene and cast polypropylene are also used.[2]