What is the difference between an incandescent and a halogen light bulb?
Halogen bulbs are technically incandescent light bulbs – illumination is produced in both when a tungsten filament is heated sufficiently to emit light or “incandescence.” The difference between the two is in the composition of the glass envelope and the gas inside the envelope. A standard incandescent bulb has a heat sensitive glass envelope that contains an inert gas mixture, usually nitrogen-argon. When the tungsten filament is heated it evaporates and deposits metal on the cooler glass envelope (this is why incandescent bulbs appear black at the end of life). This process requires incandescent bulb filaments to be heated less than optimally to give the bulb a reasonable life. The lower filament temperature gives incandescent bulbs their typical orange-yellow, warm appearing light. Halogen light bulbs utilize a fused quartz envelope (“capsule”) allowing for higher temperatures. Inside the quartz envelope is a vapor, originally iodine, now usually bromine. The tungsten filament evapo
