"Solarisation has been used since the very beginning of photography but was made famouse by Man Ray when he rediscovered the technique by accident in the 1930′s. The effect consists mainly of partially reversed tones in an image recorded on a negative or a photographic print. Basically the dark areas appear light or the light areas appear dark. The effect was usually caused by accidentally exposing an exposed plate or film to light during developing. That said, results were usually unpredictable and good results were obtained by luck and lots of practice. In this tutorial, I’m going to show you a simple way of getting similar results in Photoshop without having to lock yourself in the darkroom!"
-Photoshop Road Map
I tried a few photos out for this and none of them really "did" it for me. Here is the before picture of a paper mache skull I used before decorating it here:
here it is with solarisation: