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The Science Behind CFLs

For such a small product, CFLs have a lot of technology packed inside of them.

Each CFL has a ballast, a starter, capacitors, resistors, and a printed circuit board in the base. It also has glass tubes that hold chemicals that create the light the CFL generates. The glass tubes are coated with phosphors (up to three types) filled with argon gas and contain two metal rods (cathodes) attached with an electrode (similar to the tungsten) inside them. There are electrodes at both ends of the fluorescent tube with argon gas and mercury vapor (less than 5mg for ENERGY STAR models) contained inside.

A stream of electrons flows through the gas from one electrode to the other. These electrons bump into the mercury atoms and excite them. As the mercury atoms move from the excited state back to the unexcited state, they give off ultraviolet photons. These photons hit the phosphor(s) coating the inside of the fluorescent tube. These phosphors create visible light.

Even with all of the components and chemical reactions that take place when a CFL is turned on, ENERGY STAR qualified CFLs start in less than one second. However all CFLs have a slight warm up period of one to three minutes before reaching full brightness. This is not a flaw in the technology. The slow start-up allows the CFL to maintain constant light output while it is operating.