Photodegradation

Photodegradation, more commonly referred to by toy collectors as "yellowing," is the phenomenon by which plastics discolor over time. The process is generally started by exposure to ultraviolet light, whether from natural sunlight or fluorescent lighting. Regardless, once the process is underway, it is impossible to reverse. Photodegradation is most commonly seen on figures with bright white or light grey plastics, although it is not unknown with other colors.

In addition to there being no way to undo photodegradation, there is also no hard and fast way to determine which individual figures will be more susceptible to it. A Jetfire opened once, then left in a closet for 20 years seems just as likely to be affected as one left sitting on a shelf for the same amount of time.

Photodegradation is not to be confused with cigarette smoke residue, which also leaves a yellowish cast on plastic (and can be removed with toothpaste or other products designed to remove cigarette stains) or sun damage, a bleaching effect caused by exposure to direct sunlight (which more commonly affects packaging materials).