This is a vintage Firestone Spark Plug with a Polonium "Radioactive" Electrode in its original box. First that are entirely safe since they were alpha particle emitters when made which do not penetrate the skin and the source has a half like of 138 days. About 65 years later, they no longer emit. The idea to incorporate radioactive material into spark plugs seems to belong to Alfred Hubbard who received a patent for this concept in 1929. The Firestone Tire and Rubber Company was, I believe, the only company to actually market the idea. The first commercially available spark plugs became available in 1940. Polonium-210 was incorporated into the electrodes that formed the spark-gap of the spark plug. More specifically, the polonium was added to the molten metal (a nickel alloy) from which the wires that were used to produce the electrodes were drawn. The alpha particles emitted by the decay of the polonium would ionize the gas within the spark gap and this would presumably result in a longer and/or fatter spark. The November 1941 issue of the Science Digest reported that tests had indicated that �30 percent fewer revolutions were required to start the motor as compared with other spark plugs. According to the company's advertising, the spark plugs resulted in a smoother motor performance . . . faster pick-up . . . quicker starting . . . save more gasoline. That t was any real benefit to using these spark plugs is somewhat questionable (other than the improved performance you get whenever you install new plugs). First of all, the half-life of the polonium-210, 138 days, meant that any effectiveness would be short-lived. Second, the inevitable accumulation of deposits on the surface of the electrodes would attenuate the alpha particles and prevent them from doing their job.Near Mint and unused. Found in old store stock. Still had protector tube over electrode and metal clip over terminal. Spark plug was wrapped in instructions vellum with is wrinkled and torn since these were not carefully wrapped in the instructions since no mechanic would ever be caught reading them. Strong graphics on box and nicely marked porcelain plug. Hard to find with the box.
References: (1) Alfred Hubbard. Internal-Combustion Engine Spark Plug. U.S. Patent No., 1,723,422. August 6, 1929 . (2) Radium Spark Plugs. Newsweek March 4, 1940 , page 53. (3) More Efficient Spark Plugs. Science Digest November 1941, page 94.
A spark plug (also very rarely nowadays in British English, a sparking plug) is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed aerosol gasoline by means of an electric spark. Spark plugs have an insulated center electrode which is connected by a heavily insulated wire to an ignition coil or magneto circuit on the outside, forming, with a grounded terminal on the base of the plug, a spark gap inside the cylinder. Early patents for spark plugs included those by Nikola Tesla (in U.S. Patent 609,250 for an ignition timing system, 1898), Richard Simms (GB 24859/1898, 1898) and Robert Bosch (GB 26907/1898). Karl Benz is also credited with the invention. But only the invention of the first commercially viable high-voltage spark plug as part of a magneto-based ignition system by Robert Bosch's engineer Gottlob Honold in 1902 made possible the development of the internal combustion engine. Internal combustion engines can be divided into spark-ignition engines, which require spark plugs to begin combustion, and compression-ignition engines (diesel engines), which compress the air and then inject diesel fuel into the heated compressed air mixture w it autoignites. Compression-ignition engines may use glow plugs to improve cold start characteristics.