“BLACK LIGHT”

Gisborne Herald, Volume LXVI, Issue 20060, 5 October 1939, Page 16

“BLACK LIGHT”

STAGE NOVELTY FANTASTIC BALLET ULTRA-VIOLET RAYS USED SYDNEY, Sept, 26. A ballet dancing in “black light,” with the ballerinas “fluorescent” in dazzling colours against no visiblebackground. is a stage novelty already interesting pioneer producers. "Black light” is the physical chemist's term for the ultra-violet rays in their illumination of fluorescent substances. In the presence of these rays, which are invisible to the eye, such substances glow brilliantly in colours often different from those they show in ordinary light. For this fantastic ballet, both stage and auditorium should be in darkness. The dancers are di-essed in materials impregnated with fluorescent chemicals and perform under black light (carefully screened to exclude wave lengths harmful to the eyes). Since the human skin is far from pleasing in fluorescence, the dancers, without special jryake-up, would be gorgeous, yet a little spectral. But n their make-up contained zinc sulphide, which fluoresces effectively, their arm. and faces might display a glow oi chemical health. In black light, their teeth would glisten with a snowy whiteness. Mr. D. P. lVlellor, lecturer in chemistry at Sydney University, directed demonstrations of fluorescent effects at the University Chemical Society’s display at the Chemical Industries’ Exposition. Different Colours Fluorescent substances (now used in television screens) usually have different colours under white and under black light. Vaseline, for instance, changes in fluorescence from the honey shade to a greenish blue. Black light is being adopted to advertising signs. The paint used for these contains fluorescent chemicals, which give brilliant colours under the ultra-violet lamps. The effect is striking when darkness surrounds the signs. “Phosphorescent" substances, also seen at the exposition, are those which, after exposure to light, give off a glow in darkness. Barium sulphite, in ordinary light wlv'tc powder, shines in the dark with a blue glow. Zinc sulphide loses its phosphorescence in a few hours, but is reactivated by exposure to light. The phenomenon of phosphorescence was discovered, about 300 years ago, by a Bologna shoemaker. Brewster, in. 1845,. discovered fluorescence. He was a Scotsman, and perhaps lie dreamed of making a lost saxperice shine in Die dark.