system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do things turn pale when you put stress on them, like when you bend mechanical pencils in half?
gpt
Those pencils are made from a polymer. Polymers generally undergo a crazing process when under extreme stress. This process creates small inclusions in the material (if you zoom in you would see what looks like small cracks). The red/blue/yellow color of the pencil is only on the surface, so when these cracks appear the light that would originally hit the colored surface now hits the inner surfaces of the cracks, making it appear white.

Also, if you have a clear piece of thick plastic and you bend it, it turns white for the same reason. Light passes unobstructed through the homogenous, amorphous material, but once those cracks appear the light starts to reflect.