This frequently results in a deterioration of the physical properties such as
colour change, chalking and/or flaking but can also affect mechanical properties such as tensile and wear resistance (see Taber Abrasion).
As an example, coatings such as paints or varnishes may lose their flexibility and become brittle. Plastic decorative and structural mouldings may yellow and lose their original aesthetics as well as their strength.
When the light stability of a given material or the performance of a UV stabiliser needs to be assessed, artificial accelerated weathering tests have been developed using light sources such as daylight filtered xenon arc providing good correlation to full sunlight spectrum up to the near infra-red, or exposure to the shorter UV wavelengths only using fluorescent lamps under controlled conditions in accordance with international standards or specific test profiles that may be more suitable for a given material.