Note: The picture is rotated with an oil bath on the right. This is a sublimation of pyrene. An ultraviolet source is shining down from the top of the sublimation appartatus (purple color on left). The pyrene is highly fluorescent (light blue color). To the eye, this drowns out the contrast between the purple UV source and the blue fluoresence of pyrene But to a camera, a better contrast can easily be seen.