Ever walk into a room, turn on the lights, and think, “This is really not as bright as I would like it to be,” then walk out and come back later to find the lighting is actually just fine? The reason for this lag in full brightness is the same whether for a commercial office project lighted with compact fluorescent (CFL) downlights, or at home where screw-in base retrofit CFL lamps have been used in formerly incandescent table lamps and pendants. That reason – amalgam technology.
I know you’re thinking that this is just not going to be something you need to know – unless you are trapped at a really boring party – but as fluorescent lamps become de rigueur in replacing inefficient incandescent lamps, it really is good to know a little bit about their inner workings.
All fluorescent lamps, whether linear tube or compact fluorescent lamps, contain MERCURY. The mercury, when heated by the incoming electrical current, is vaporized and converts electrical energy into ultraviolet radiation. The phosphor coating on the inside of the glass tube absorbs the ultraviolet radiation, and converts it into visible light.
In linear fluorescents, mercury is provided in a liquid or pellet form. But all of the twists and bends in a CFL cause liquid mercury to pool when the lamp is installed in different orientations. As a result, the mercury does not vaporize or distribute effectively. To resolve these issues, amalgam technology, in which mercury is imbedded in a metal alloy, was created to allow more stable light output, independent of burning position. Since the mercury is contained within the amalgam, the lag time to heat the amalgam and release mercury vapor creates the lag in light output; CFL lamps will take as long as 110 seconds to produce 80% of their total lumen output.
Mercury is the dark side to the green story of fluorescent lighting; it’s essential, and it’s a poison. During the lifetime of a lamp, the mercury that is available to be energized is used up – bonded to the glass and phosphors. This reduced level of mercury will, for a time, allow the lamp to create light, but not enough to overcome the presence of the argon gas within the tube, resulting in a fatal, eerie bright pink glow.
The glass tube of the fluorescent lamp does create a sealed environment, so although the lamp no longer produces useful light, mercury is still present. Should a lamp break, whether linear or CFL, extreme care should be taken in disposing of not only the shards of broken glass, but also the powdery phosphors, which have now bonded with vaporized mercury.
Even though some lower-mercury lamps labeled as TCLP compliant are touted as having mercury levels lower than those regulated as hazardous waste, and could avoid additional disposal costs, recycling is still the best way to allow mercury to be reclaimed and stay out of the landfill environment. Recycling of screw-in base compact fluorescent lamps also allows the ballast components in the base of the lamp to be recycled.
And while amalgam technology allows for better recycling of mercury, it does mean that slightly more mercury is going into the lamp system. The LEED program is now allowing Innovation in Design credits to be awarded for the use of low-mercury lighting. This recognizes that while mercury is a fact of life in energy-efficient lighting, there are ways to minimize the total amount of mercury on a project (this includes high-intensity discharge lamps as well). Satisfying this credit entails meeting the target maximum for mercury content, and ensuring that 90% of the lamps purchased for a project comply with this target level – this puts amalgam technology CFLs at a disadvantage compared to linear fluorescents.
So, think incandescent lamps are a way to avoid this messy bit of mercury business? While incandescent lamps do not require mercury to operate, fluorescent lamp and sustainability advocates have computed the theoretical environmental mercury exposure created by the use of incandescent lamps powered by electricity from coal-burning power plants. This number is over three times the amount from compact fluorescent lamps.
“Amalgam for Use in Fluorescent Lamps Comprising Lead, Tin, Mercury Together with Another of the Group Silver, Magnesium, Copper, Nickel, Gold and Platinum. – US Patent 5952780 Description.” PatentStorm: U.S. Patents. 14 Sept. 1999. Web. 15 Oct. 2010.
“Amalgam Technology.” Megaman Global: Green Room. Web. 15 Oct. 2010.
“Compact Fluorescent Lamp.” Wikipedia, the Free Encyclopedia. Web. 15 Oct. 2010.
“Fluorescent Lamp Containing a Mercury Zinc Amalgam and a Method of Manufacture – US Patent 5882237 Description.” PatentStorm: U.S. Patents. 16 Mar. 1999. Web. 15 Oct. 2010.
“Fluorescent Lamp.” Wikipedia, the Free Encyclopedia. Web. 15 Oct. 2010.
Harris, Tom. “HowStuffWorks “How Fluorescent Lamps Work””. Howstuffworks “Home and Garden” Web. 15 Oct. 2010.