In good light conditions, the colour change is just about detectable with the human eye.
The testing examined changes in colour and gloss, due to the effect of ultraviolet radiation (UV radiation) and moisture, on a surface painted with petroleum-based oil paint. The tested colours were red (TM-7742), yellow (TM-7411) and green (TM-7821).
The samples were exposed to 1 000 hours of ultraviolet radiation, in which the radiant power of UV radiation corresponds to the radiant power of the sun on a bright summer day. The amount of energy of the UV radiation accumulated is, on average, of the same magnitude as the amount of energy accumulated on a horizontal plane during the period of one year in Southern Finland. The temperature of a yellow paint surface during the test was about 50–55°C. The test also included a 24-hour moisture stress. The test method is based on the ISO 4892-3 standard.