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CFL Background

Color temperature

The lower the color temperature, the warmer the light. Warmness (red) or coolness (blue) can be measured in degrees Kelvin by a chroma meter.

We observed a temperature of about 2800 K for soft white bulbs, whereas "daylight" bulbs measured around 3500 K — real noontime sunlight ranges from 5000 K to 6600 K.

Lumens vs. lux

Manufacturers use a complex process to measure lumens, the total quantity of light emitted by a bulb.

Watts and efficiency

All CFLs use about 70 percent less electricity than incandescent bulbs. The average U.S. household has 45 light bulbs — replacing that number of 75-watt incandescent bulbs with CFLs would save $180 per year.

Phosphor

This chemical compound lines the inside of CFL tubing. When excited, it converts ultraviolet radiation into visible light. The chemical composition of the phosphor determines the color temperature of the light emitted by the bulb.

Mercury

According to the EPA, CFLs contain an average of 5 milligrams of mercury, which increases the bulb’s efficiency. But that also means you can’t just trash them—CFLs must be properly recycled.  Check out this web page on the EPA website at http://www.epa.gov/bulbrecycling/