The Heating Mechanism
Although experimenting with bubbling liquids in sealed tubes goes back to as early as Benjamin Franklin, the first recorded invention of the technology for bubble lights came from Raffaele Fioravantl, who used a heating element in close proximity with a vaporizing chamber. When the bubble light was plugged in, the electricity illuminated the heating element. The liquid in the vaporizing chamber would begin to heat. This chamber was connected to a visible, translucent bulb via glass tubes, shaped like a backwards J, and when the liquid heated, bubbles would form and enter the upper bulb.
Carl Otis adjusted his own design for bubble light technology. Otis's design included a porous wooden plug that was permanently held at the bottom of the translucent tube. Several small chambers of the chemical were placed close to the heating source, which provided for a more effective and efficient boiling time. He then took this design for a large bubble sign and adjusted it for Christmas tree decoration. The electric company NOMA bought Otis's patents and designs, and licensed Otis to continue development. Otis's design for Christmas lights included a low-wattage bulb that could operate on about 15 volts in order to fit the standard home electricity output. However, instead of a wooden plug, Christmas tree bubble lights used loose glass plugs.
Originally, Otis's design included a convex sphere on the end closest to the heating source. However, in later developments, NOMA flattened the end of the translucent tube to make for more efficient heating. It also exchanged the glass plug for a chemical compound or glass beads, allowing for quicker heating.
Bubble lights function because a heating element heats a certain liquid with a low boiling point. As the liquid sits close to the heating source, it begins to warm. Plugs, chemical compounds or glass expedites this process by conducting the heat. Once the liquid reaches the boiling point, bubbles form and pass through the length of the translucent tube.
Early forms of liquid in bubble lights included alcohol or ether; it could be colored based on preference. Since the late 1940s, bubble lights are now most often made with methylene chloride.
The Translucent Bulb
A translucent bulb, attached to the heating element and filled with liquid, provides the entertainment of bubble lights. Some tubes are colored; other tubes are completely clear with colored liquid.