Incandescent light bulb Small variations in resistivity along the filament cause "hot spots" to form at points of higher resistivity; a variation of diameter of only 1% will cause a 25% reduction in service life. These hot spots evaporate faster than the rest of the filament, which increases the resistance at that point—this creates a positive feedback that ends in the familiar tiny gap in an otherwise healthy-looking filament. Irving Langmuir found that an inert gas, instead of vacuum, would retard evaporation. General service incandescent light bulbs over about 25 watts in rating are now filled with a mixture of mostly argon and
Phase-out of incandescent light bulbs their color temperature may not lower, as it does with incandescents. Phase-out of incandescent light bulbs Governments around the world have passed measures to phase out incandescent light bulbs for general lighting in favor of more energy-efficient lighting alternatives. Phase-out regulations effectively ban the manufacture, importation or sale of incandescent light bulbs for general lighting. The regulations would allow sale of future versions of incandescent bulbs if they are sufficiently energy efficient. Brazil and Venezuela started the phase-out in 2005, and the European Union, Switzerland, and Australia started to phase them out in 2009. Likewise, other nations are implementing new