Quote Originally Posted by 68Charger View Post
yeah, the media is full of chemistry experts...

if it's something that shows up when the skin of the plane gets hot (like when the APU is powered up), then it could be LEMON JUICE (remember the old invisible ink as a kid?)

just something that changes temperature when it gets above a certain temperature.
That was the other part that made little sense to me ...


with the exception of leading edges of the wings / nose the skin of the aircraft will COOL not heat in flight ( well unless it is in the jet blast of the engine or the exhaust of the APU of course) I suppose the engine nacelles gets warm also.