A short notice in the Phrenological Journal from April, 1879, reports on the self-luminous properties of calcium sulfide. A Prof. Morton from the Stevens Institute of Technology had analyzed the material painted onto the faces of self-luminous clocks and discovered that it was just a “sulfide of calcium.” The compound absorbs light when exposed to sun or artificial light. It then glows in the dark. Seemingly miraculous, one dial covered with this compound continued to glow for five days after it had been removed from light.
Professor Morton was enthusiastic about the possibilities:
Professor Morton (and the person reporting on Morton’s work) seems to be, perhaps, a bit optimistic. I doubt that calcium sulfide would ever give off enough light to “obviate need” of any artificial lighting. Moreover, given the eerie red glow typically emitted by calcium sulfide, it would be like living in a horror movie.
If, however, you want to try to reduce your electric bill by painting the inside and outside of your house with calcium sulfide, here’s how you can make your own from oyster shells.