Quick History of the Spark Plug

Spark Plug Sketch   The actual evolution of the modern day spark plug came about as a solution to the problem with early flame and ignitor   ignitions on internal combustion engines. There have been several materials that have evolved as insulation materials.   Some materials that have been used are mica, stone and several different kinds of improved porcelain. A lot of early   forms of porcelain were not designed to handle the extreme hot and cold changes that engines demanded. Some
  insulated materials were very porous and would absorb oils and soot easily. This would make for a short life as they   would foul out quickly. Gasoline in the early days wasn’t as refined as it is today. It contained more oils and was closer
   to today’s kerosene.

  In 1915 a major improvement in porcelain was “775” porcelain, by the Frenchtown Porcelain Co..Spark Plug Sketch
  This new formula produced porcelain that would hold up to heat changes with less
  absorption of oil. Since that time improvements have continued on porcelain designs.
  Dr. Joseph Jeffery’s discovery of silimanite in 1933 gave spark plugs a longer life. This
                             was a major improvement in the porcelain design.

Over the years, companies have tried to come up with unique designs to be used as selling points for their
spark plugs. Some of the unique idea results were the:

  • Quick Detach – by moving a lever 1/4 of a turn, you could remove the center for quick easy cleaning without tools;
  • Double Ended Plugs – could be turned over when one end was fouled and still have a plug that worked;
  • Breathing Plugs – were designed to allow clean, cool air to be sucked in over the hot end of the porcelain, which would assist in further burning away of deposits;
  • Priming Plugs – allowed you to put a small amount of gas into the cylinder for easy starting;
  • Coil Plugs – where the coil and the plug were actually combined into a one piece unit;
  • Intensified Plugs – having a second firing gap, that was advertised as allowing the plug to “fire hotter and longer”.