From the 1930s through the 1970s, Aerolux Light Corporation produced these amazing novelty light bulbs that contained sculptural filaments in the shape of flowers, birds, and myriad other designs that would illuminate in different colors. The bulbs contained a mixture of neon or argon (or both) and some of the components were coated with phosphors to achieve different color effects. Via Wikipedia:
Aerolux gas discharge light bulbs contained low pressure gas, either neon or argon, or a mixture of the two. Also within the bulb were metal sculptures coated with phosphors. These phosphors fluoresced when excited by glow discharge. Because glow discharge occurs readily at 110-120 volts AC, one could use these bulbs in standard household lamps in the United States.
The phosphors used in the bulbs were somewhat brittle, necessitating care in handling. Shaking or jarring the bulbs would cause flaking and migration of the phosphors to other parts of the metallic sculpture. Such handling would leave non-fluorescing portions of the sculpture and/or migration of phosphors to other surfaces within the bulb.
At the height of production some of the bulbs sold for a mere .20 cents, but can now fetch hundreds of dollars on Ebay or Etsy. If you happen to be in New York you can see a bonafide Aerolux bulb that’s on permanent display at MoMA as part of an artwork by artist Dan Flavin. (via Neatorama, Geyser of Awesome, Oddity Central)