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How Light Bulbs Are Made

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the incandescent light bulb is a rather

simple device its base has two metal

contacts which connect to a metal

filament the electric currents electrons

collide with the atoms in the filament

making them vibrate this energy heats

the atoms to 4,000 degrees Fahrenheit at

which temperature they emit visible

light the light bulb Factory has two

production lines that eventually merge

one prepares the glass ball the other

makes what's called the mount the

electrical components that go inside it

at the start of the mount line a machine

cuts glass tubing into pieces of

specific lengths the cut tubes land on

what's called a glazing wheel that runs

them through a gas flame for about seven

seconds this heats the glass enough to

smooth the surface the glazed tubes now

enter what's called a flare making

machine which heats each tube until the

glass is malleable then stretches one

end into a flared shape

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the next machine loads to copper lead

wires into the flare end then it inserts

a thin glass cylinder called the exhaust

tube a trip through a series of

progressively hotter flames softens the

tubes a press then moves in to squash

them encasing the wires in glass at the

same time the machine makes a tiny hole

in the glass in between the wires this

is to later remove air from inside the

ball

it'll exit via the exhaust tube through

this hole next the machine separates the

lead wires and forms the ends into hooks

these fastened to the filament a thin

wire coil made of tungsten a type of

metal that holds up well to heat the

machine coats the lead wires in a liquid

form of another metal zirconium this

lengthens their lifespan by making them

more resistant to moisture inside the

ball like the tubes we've just seen the

bulbs are made of an inexpensive type of

glass called soda lime glass a machine

stamps the top of each bulb with the

voltage the wattage and the company logo

opaque light bulbs are simply clear

bulbs with an inside coating of

synthetic silica a white powder the

coating machine charges the bulbs to

30,000 volts combined with just the

right amount of heat this electrical

charge makes a thin layer of powder

cling to the glass a series of flames

evaporates moisture and bakes off any

impurities

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as the two production lines merge a bob

goes over each mount torches then fuse

the flare to end of the mount to the

neck of the ball arms move in and mold

the neck to fit inside the bulbs

aluminum base the next machine vacuums

out all the air and the ball and

replaces it with pressurized argon gas

this inert gas will resist heat buildup

helping the filament last longer after

bending the lead wires out of the way

torches melt and seal off the glass

exhaust tube locking the argon gas

inside the bulb would now be fully

functional if connected to an electric

current but it needs a base in order to

screw into the socket of a light fixture

the base is made of aluminum this

machine inserts one of the bulbs lead

wires through the middle and soldered it

in place it then spot-welds the other

wire to the side the result two base

contacts to line up with two socket

contacts

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on their way to packaging the bulbs

undergo what's called flash testing

repeated light ups using a higher

voltage each time this strengthens the

filaments inside making it less likely

to break during shipping

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