Gold coatings have excellent and consistent reflectivity in the infrared and good reflectivity in the visible regions. Protected gold coatings offer a durable finish that provide 96% reflectivity. Protected gold helps to protect the mirror from damage and makes it easier to clean.
Unprotected gold coatings provide a higher reflectance than protected gold but they are much more delicate. These mirrors can be used in applications where the polarization state needs to be strictly maintained or to prevent dispersion due to the overcoat of protected gold mirrors.