“CFL” is a household name at this point. Developed in 1985, the compact fluorescent light bulb is now a 25-year-old product present in 70 percent of homes in the United States. Just last year, more than 273 million CFLs were sold in the U.S.
Cold cathode fluorescent light bulbs are a little less familiar, at least to the general public. Here’s a quick overview of the core differences.
All fluorescent light bulbs have two cathodes (one at each end). In a standard CFL, the cathodes are made of coiled tungsten filaments that are heated to approximately 900 degrees Fahrenheit each time the light bulb is turned on. That heat releases electrons. The electrons shoot back and forth between the cathodes and react with the mercury to create ultraviolet radiation, which in turn reacts with the phosphor coating on the inside of the glass envelope to create light. Standard CFLs are hot cathode light bulbs.
In a cold cathode fluorescent light bulb, the cathodes are made of a solid metal thimble, which is more durable than the thin coils in standard CFLs. The cathodes only heat up to about 200 degrees Fahrenheit (certainly not “cold”, but relatively cooler than the hot cathode filament, hence the name). The voltage potential within the tube excites the mercury to cause current flow.