Apple Keyboard + UV Light

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http://vimeo.com/11590242 I have a question for all material scientists & plastic experts.  I have an Apple wireless keyboard and a near-UV LED flashlight.   As one would expect, many things fluoresce:  tee shirts, white paper, etc.  What is odd, is that only some of the keys on my keyboard do this.  I would expect this to be an all-or-none type deal but specifically the F,J, arrows, Cap locks, function, alt, control and return keys glow while the others do not.  Under normal light these keys look identical and feel the same.

Why would Apple use a different material for these keys?  (My wired Apple Keyboard does the exact same thing.)  Does anyone know why there is this difference?

The unusual keys:

  • J
  • F
  • Cap Lock
  • Fn
  • Control
  • Alt / Option
  • Enter / Return
  • arrow keys