
Originally Posted by
kup
Just to mention that it actually took two years to yellow again (wow I didn't realize it had been that long!), it wasn't a sudden thing.
That's why the whole thing seems strange to me. The toy had been kept in constant darkness ever since I whitened it. My guess is that although sunlight (artificial light) may expedite the process, yellowing can occur despite of it just for being exposed to air.
As we know, some plastics are more prone to yellowing than others so maybe some will mostly be affected by sunlight while others just need to be exposed to air to yellow.