Heat Sensitive Paint - Pretty Cool

[C.A.R.]

no the bonnet would only have a splodge on it if the rest of the rest of bodywork had cooled right down to black

its NOT reactive to heat...it reacts to cold

Precisely why I wrote what I wrote. In the winter you often have ice on the bonnet of the car which is impossible to clear before setting off. As the engine warms up it clears a splodge in the middle. With last winter there were several occasions where the 20-mile trip to work could be completed without the car thawing out completely - but the bonnet would still have a patch...

So it'd look stupid in the winter.