What is required to make them?
- Tungsten Filament - The filament is manufactured through a process known as drawing, in which tungsten is mixed with a binder material and pulled through a shaped orifice into a fine wire. Next, the wire is wound around a metal bar called a mandrel in order to mold it into its proper coiled shape, and then it is heated in an process known as annealing. This process softens the wire and makes its structure more uniform. The mandrel is then dissolved in acid. The coiled filament is attached to the lead-in wires.
- Glass Bulb - The glass bulbs are blown by a ribbon machine that can produce more than 50,000 bulbs per hour. After the filament and stem assembly are inserted into the bulb, the air inside the bulb is evacuated and an argon/nitrogen mixture is pumped in. Finally, the base is sealed on.
- Base - The base of the bulb is also constructed using molds. It is made with indentations in the shape of a screw so that it can easily fit into the socket of a light fixture.
- Once the filament, base, and bulb are made, they are fitted together by machines. First, the filament is mounted to the stem assembly, with its ends clamped to the two lead-in wires. Next, the air inside the bulb is evacuated, and the casing is filled with an argon and nitrogen mixture. These gases ensure a longer-life for the filament. The tungsten will eventually evaporate and break. As it evaporates, it leaves a dark deposit on the bulb known as bulb-wall blackening.
- Finally, the base and the bulb are sealed. The base slides onto the end of the glass bulb such that no other material is needed to keep them together. Instead, their conforming shapes allow the two pieces to be held together snugly, with the lead-in wires touching the aluminum base to ensure proper electrical contact. After testing, bulbs are placed in their packages and shipped to consumers.
How are light bulbs used and how long do they last?
What happens to light bulbs when they are no longer needed. How do they impact the environment?
Many fluorescent bulbs contain toxic levels of mercury which can cause a lot of harm. For fetuses, infants, and children, the primary health effect of methylmercury (a common compound of mercury) is impaired neurological development. Methylmercury exposure in the womb, which can result from a mother's consumption of a fish or shellfish that contain methylmercury, can adversely affect a baby's growing brain and nervous system. Impacts on cognitive thinking, memory, attention, language, and the fine motor and visual spatial skills have been seen in children exposed to methylmercury in the womb.
Many bulbs also contain lead levels exceeding hazardous waste limits. If they’re thrown away in the regular garbage, this lead will sooner or later find its way into nature. Lead is acutely and chronically poisonous to aquatic organisms and mammals. Even in small concentrations, lead poisoning may cause neurotoxic and immunologic problems. Lead can also cause fetal damage in humans and reduce fertility. Lead accumulates in fish and mammals over time, and is only released at a very slow rate. Humans are mainly exposed to lead through polluted air and food.
Most bulbs have paper covers which can be recycled so their impact on the environment is minimal and after disposing them, they are probably used to make more paper.
How can light bulbs be reused or repurposed?
What are the impacts of reducing, reusing, and recycling light bulbs?
Coy, Peter. "Light Bulbs to Make America Really Stingy with the Juice." Business Week. April 25, 2015, p. 91.
Miller, William H. "The 20-Year Light Bulb Clicks On." Industry Week. April 25, p. 41.
Pargh, Andy. "Light Bulbs Shed New Light." Design News. April 25, 2015, p. 164.
Friedel, Robert. Edinson's Electric Light: Biography of an Invention. Rutgers University Press, 1987.