Dark yellowing

Dark yellowing is a phenomenon that occurs with certain paint films if they are stored for a long time without exposure to light. The originally clear or light-colored paint film turns yellowish, which is particularly visible on light-colored or white coatings. This effect is an undesirable sign of ageing and can impair the aesthetic quality and visual impression of the coated object.

The main cause of dark yellowing is the chemical change in the binders in the paint film, particularly in the case of alkyd resin-based paints. These resins tend to oxidize under the influence of oxygen or through interaction with other chemical components in the lacquer, which causes the yellowish discoloration. Light, especially UV radiation, can partially reverse this effect, as the light energy breaks down the degradation products in the lacquer.

To minimize dark yellowing, modern paint formulations are often provided with special additives or modified resins that are more resistant to oxidation. It is also recommended that painted surfaces are stored in translucent rooms and that excessive heat or moisture, which can accelerate the ageing process, are avoided. Dark yellowing is a particular challenge in decorative applications, such as furniture or interior coatings, where a long-term unchanged color effect is desired.