head (C), where the fuel is heated and vaporized. The kerosene vapour is then forced under pressure through the descending tube (D) to the vapor nozzle (E); here it sprays through a jet in the middle of the burner, where it mixes with air and burns in a sootless blue flame. The heat from that flame vaporizes more fuel to sustain the process when the spirit cup burns out. The user can pump the tank more to increase the pressure and make the flame larger; turning a small "air screw" (usually located in the filler cap) will release pressure from the tank and make the flame smaller. If no alcohol is available for lighting, a twist of cloth or even dry grass will form a wick in the spirit cup. Pumping once will dispense a small amount of kerosene to dribble down into the cup which will then light using the wick. As the flame dies down, a further gentle pump will either ignite the main burner or dispense more kerosene into the spirit cup. Prior to the introduction of the Primus, kerosene stoves were constructed in the same manner as oil lamps, which use a wick to draw fuel from the tank to the burner and which produce a great deal of soot due to incomplete combustion. The Primus stove's design, which uses pressure and heat to vaporize the kerosene before ignition, results in a hotter, more efficient stove that does not soot. Because it did not use a wick and did not produce soot, the Primus stove was advertised as the first "sootless" and "wickless" stove. See also Jetboil Portable stove Tilley lamp References External links Primus Classic Camp Stoves Old Camp Stove User's platform (French) Camping equipment Stoves Portable stove manufacturers Swedish inventions