Sun/UV Damage Examples
Like most other kinds of art, production animation art is sensitive to UV light. For art on paper, the damage usually presents as yellowing or other discoloration. These two sketches were held in a double frame (supposedly with archival quality glass/materials) and displayed in a Warner Bros. gallery before being purchased and displayed in someone's home. One side of the frame was commonly exposed to sunlight, while the other was mostly in shadow. As you can see, the sketch exposed to sunlight shows significant discoloration.
UV damage to cels will normally present as line fading. Hand drawn cel lines began falling out of popularity following the advent of Xeroxed line work in the early 1960s. The big downside of Xeroxed line work is that the pigment can be very fragile and may degrade quickly in sunlight. Below are a few examples.
Collector's Note: Line fading can happen even without continued exposure to sunlight. However, it will greatly speed up the process.
This cel from Batman TAS shows an almost complete loss of the line work. Note the lack of facial features.
This cel of the Penguin shows partial line fading. It gives the lines a broken look.
Again, this cel from Fern Gully shows an almost total loss of lines.