Shortly after WW II (1945-1946) a person named Ed Chamberlin formulated and developed a potent new model engine fuel called "Liquid Dynamite".

The fuel testing was done using the Bantam .19 engine. During the test Ed and Ben shut the ignition off and to their amazement the engine kept running. Removing the spark plug they realized that the ground electrode had broken off and the center electrode was glowing red hot, which allowed the engine to continue running, using the hot new fuel.

Ben Shereshaw, ever the engineer, experimented and wound small nichrome wire elements to replace the center electrode therein making an early prototype glow plug; however the nichrome material did not prove successful and burned out very quickly.

During this same time period, Ray Arden was also experimenting with the same fuel on his Arden .19. Ed Chamberlin excitedly advised Ray of his and Ben's discovery. Ray experimented further and discovered that an alloy of platinum and iridium wire provided a superior catalyst for methanol and the modern glow plug was officially born.

Ben Shereshaw made a manufacturing agreement with Ray Arden and Ben thereafter produced millions of glow plugs under the brand name of XL for the OK-Herkimer Company in his Miniature Motors factory.

Glow plugs are used to heat the combustion chambers of diesel engines in cold conditions to help ignition at coldstart. In the tip of the glow plug is a coil of a resistive wire or a filament which heats up when electricity is connected.

Glow plugs are required because diesel engines produce the heat needed to ignite their fuel by the compression of air in the cylinder and combustion chamber. Petrol engines use an electric spark plug. In cold weather, and when the engine block, engine oil and cooling water is cold, the heat generated during the first revolutions of the engine is sapped away by the cold surroundings, preventing ignition. The glow plugs are switched on prior to turning over the engine to provide heat to the combustion chamber, and remain on as the engine is turned over to ignite the first charges of fuel. Once the engine is running, the glow plugs are no longer needed.

In-direct injection diesel engines are less thermally efficent due to the greater surface area of their combustion chambers and so suffer more from cold-start problems. They require longer pre-heating times than direct-injection engines, which often do not need glow plugs at all in temperate or hot climates even for a cold start.

In a typical diesel engine, the glow plugs are switched on for between 10 and 20 seconds prior to starting. Older, less efficent or worn engines may need as much as a minute (60 seconds) of pre-heating.

Large diesel engines as used in heavy construction equipment, ships and locomotives do not need glow plugs. Their cylinders are large enough so that the air in the middle of the cylinder is not in contact with the cold walls of the cylinder, and retain enough heat to allow ignition.

Modern automotive diesel engines with electronic injection systems use various methods of altering the timing and style of the injection process to ensure reliable cold-starting. Glow plugs are fitted, but are rarely used for more than a few seconds.

Glow plug filaments must be made of materials such as platinum and iridium that are resistant both to heat and to oxidation and reduction by the burning mixture.

In model aircraft, glow plugs are used for starting as well as continuing the power cycle. A small voltage (around 1.5 volts) is applied to the glow plug, the engine is then started, and the voltage is removed. The burning of the air/methanol,nitromethane mixture keeps the plug hot, and allows it to ignite the next mixture. Since the ignition timing is not controlled electrically, as in a spark ignition engine or by fuel injection, as in an ordinary diesel, it must be adjusted by the richness of the mixture, the ratio of nitromethane to methanol, the compression ratio, the cooling of the cylinder head, the type of glow plug, etc.