02x07 - Carpets/Drinking Water/Laser Eye Surgery/Acoustic Guitars

[bunniefuu]

Narrator: Today on
"how it's made,"

carpets,

drinking water,

laser-eye surgery,

and acoustic guitars.

People use the words "rug"
and "carpet" interchangeably,

but they're not the same thing.

A rug covers just
part of the floor.

A carpet goes wall to wall.

Today most carpets on the market
are made of synthetic materials.

The first step is to
make the carpet yarn.

They start by feeding bales
of nylon or polyester fiber

into the opening
and blending machine.

The carding machine then
untangles the individual fibers,

lining them up in neat rows,

then gathering
them into wider bands.

The bands go into cans.

From the cans,

they go into a machine
called a drawing frame...

Which draws out five threads

to make one rough, loose thread.

That thread goes onto spools.

Then they twist
threads from two spools

to make a stronger
and thicker thread.

Next they twist two of
those threads together

to form a two-ply yarn.

To ensure the two
plies don't untwist,

the yarn goes through
a heat-setting machine

at almost 270
degrees fahrenheit.

The continuous heat
permanently sets it,

much the way a
curling iron sets hair.

After 45 seconds
of heat-setting,

the yarn is rewound on spools.

Those spools then go
to the tufting department,

where the carpet-making begins.

A standard 144-inch-wide carpet

is made from 1,440
spools of yarn.

Each spool feeds
into a plastic tube,

which feeds into
the tufting machine,

where the 1,440 lines of yarn

feed 1,440 tufting needles.

The needles stitch the yarn

into a canvas backing
made of polypropylene.

With slow motion,

you can see the yarn
being hooked on the canvas

then cut underneath
into carpet pile.

Up to 12 needles work
each inch of canvas.

The result is a pile carpet
in the standard 12-foot width.

Next they dye it.

For multicolored carpets,

they use a machine
called a chromojet.

It works much the way a
computer ink-jet printer does,

forcing streams of
dye in different colors

into the carpet fibers.

The more complicated
and colorful the design,

the more often the machine
passes over the carpet.

For solid-color dyeing, there's
a mixer in each dye reservoir

to keep the color even.

They soak the carpet
for four hours

in a hot bath of dye and water

heated to 212
degrees fahrenheit.

Another method uses heat
and air pressure in an autoclave.

What the bath method
does in four hours,

this method does
in just 30 minutes

and with more carpets at a time.

Once the dyeing is finished,

they apply a water-based
glue to a polypropylene backing

then put the backing over
the original canvas backing,

locking the carpet
fibers in place.

Then it's on to what's
called the marriage roll,

a roller press that marries
the two backings together.

After a quick run
through an oven

to make the water
and the glue evaporate,

they cut the finished
carpet into rolls.

A standard roll
is 100 feet long.

Narrator: Researchers have
invented a pollution-free car

that runs on hydrogen.

The research team modified
the standard car engine

to burn hydrogen
instead of gasoline.

Now they have to figure out

how to prevent the hydrogen
tank from blowing up in a collision.

Drinking water that's fresh,
clean, and crystal-clear

is something many of
us take for granted.

We might not give
it a second thought,

but between the
source and our tap,

a lot happens to make
that water fit to drink.

Our water may come
from mother nature,

but it's far from pristine.

It starts its journey
to the treatment plant

through a water-intake pipe.

On the wall of that
pipe, about 6 1/2 feet down,

is a 6-inch hole.

Covering that
hole is a metal grill

designed to keep out large
debris, such as tree branches.

The water flows to
the pumping station,

where it goes through
a preliminary screening.

A giant revolving screen
removes fish, garbage, and grass.

Once they remove the debris,

a low-pressure pump moves the
water into the treatment plant.

The untreated water,
called raw water,

is dirty and smelly.

They first add a powerful form
of the chemical element carbon

called activated carbon.

It absorbs contaminants
such as solvents and pesticides.

That rids the water
of bad taste and odor.

From there,

the water then goes through
a series of mixing tanks.

The first tank holds a chemical
called aluminum sulfate.

It acts as a coagulant,

a substance that
thickens liquid into globs.

In the raw water,

the aluminum sulfate forms
tiny, sticky globs called flocks.

Bacteria, mud, and
other impurities

stick to those flocks.

Then the flock-filled water

moves on to the
second mixing tank.

The second tank holds a
chemical called polymer,

which is essential to the
next step of the process,

called sedimentation.

Five pipes inject the water
with superfine particles of sand,

called microsand.

The polymer coats the
sand, making it sticky.

The grains of sand then stick
to the flocks in the raw water,

weighing them down even more.

The water then flows
into a settling tank,

where the flocks,
because they're heavier,

settle to the bottom.

You can see the result
in this demonstration.

The water is finally clear,
but it's far from drinkable

because it's still full
of bacteria, viruses,

and other organic matter.

So, on to the next
step -- filtration.

The water flows onto
the top of the filter

then trickles downward,

passing through a layer
of anthracite, a type of coal,

then through a layer of sand.

This filters out any
remaining particles,

which then flow to the middle.

But the water is still teeming
with bacteria and viruses,

so it has to be disinfected.

They add 1.9
milligrams of chlorine

for every 4 cups of water,

enough to k*ll off
those germs and bugs.

Then they add a
mineral called silicate

to prevent calcium buildup
from blocking our water pipes.

The treatment plant

sends water samples to
a government inspector,

who continuously
monitors the water supply

to ensure it meets
safety standards.

The amount of chlorine
remaining in our drinking water

is 20 millionths of
an ounce per liter.

The chlorine gas the
plant uses is highly toxic.

Should any leak out,

emergency teams would
have to evacuate a 6-mile radius.

So the plant stores
the drums of chlorine

in a high-security area.

It's taken about 45 minutes

to turn raw water
into treated water.

Now these electric motors

will pump it through underground
pipes, right to your tap.

Narrator: Short-sightedness,
far-sightedness, and astigmatism

are all due to light
not focusing precisely

onto the retina.

Surgeons can correct
this by using a laser

to reshape the curvature of
the front surface of the eye,

called the cornea.

The surgeon operates
on one eye at a time.

He cleans the eye, the lid,
and the lashes with antiseptic...

And administers anesthetic
drops to freeze the eye and lid.

He opens the lid
wide with a speculum

then rinses the eye
with a saline solution.

Everything's frozen, so the
patient doesn't feel a thing.

Next -- antibiotic drops
to prevent infection.

Before every operation, the
surgeon tests the equipment.

He fires the laser
on a metal plate

to test its energy level.

The surgeon administers a
few more anesthetic drops...

...then inspects
the microkeratome,

the device he'll use
to lift a very thin layer

from the outer
surface of the eye.

He also measures
the patient's cornea

using an ultrasonic instrument.

The cornea must be
a minimum thickness

for it to be safely reshaped.

The surgeon uses the speculum
again to prop the lid open.

Then he begins the operation.

He marks the eye
with sterile ink,

reference marks he'll use later.

Next he positions a metal
ring around the cornea.

The ring is attached
to a suction pump

so it clings to the eye.

Like holding a tomato
steady while you slice it,

it holds the eye steady while
the surgeon cuts the tissue.

The surgeon lubricates
the eye with sterile water

then mops up the excess water
with a small, absorbent sponge.

Then he takes the microkeratome

and slips it into grooves
in the metal suction ring.

In a matter of seconds, the
device moves across the eye,

cutting open a flap of tissue,

the same way a carpenter's
plane shaves a layer of wood.

The surgeon uses a
sterile sponge ring

to keep tears from
contaminating the cornea.

He folds back the flap of
tissue, exposing the cornea.

He mops up the excess liquid...

...then starts up the laser.

Meanwhile, a tiny sponge
keeps the flap moist.

The laser, an invisible light,

fires in pulses -- 50
pulses per second.

Each pulse vaporizes
an area of corneal tissue


of an inch thick.

The laser has been
computer-programmed beforehand

so it knows exactly how
to reshape the cornea

to give most
patients 20/20 vision.

In less than a
minute, it's done.

The surgeon removes the sponge

and then using those little
ink marks he made earlier

as reference points,

folds the flap back
to its original position.

If the flap isn't precisely
where it was before,

the patient will
have distorted vision.

Using a syringe that flushes
the area with sterile water,

the surgeon carefully
smoothes the flap

the same way you'd
smooth out a tablecloth.

Then he removes the sponge ring.

Within 45 seconds,

the negative pressure inside
the cornea sucks the flap back on.

The flap literally seals itself.

With a sponge, the surgeon
dabs up any excess water.

He applies antibiotic drops
as a preventive measure

then inspects the
microkeratome again

before moving on
to the other eye.

He takes the speculum
off, tapes the eye closed,

then performs the same
operation on the other eye.

When that's done, the surgeon
uses a high-powered microscope

to make sure the
flaps are wrinkle-free.

The patient wears protection
shields until the next morning

then overnight for a week.

Narrator: The best guitars come
from trees about 800 years old,

trees with enough
rings in their trucks

to provide wood with a
tight and straight grain,

wood flexible enough to vibrate,

yet strong enough to withstand
the pull of the guitar strings.

The guitar traveled from
North Africa to Europe

with the moors, who invaded
Spain in the 8th century.

In time, the guitar became
the signature instrument

of Spanish Flamenco music

and the trademark
of the singing cowboy.

In the 1930s,

the acoustic guitar
debuted as a jazz instrument.

By the 1960s, as the electric
guitar took over rock 'n' roll,

the acoustic guitar remained a
staple of the folk-music scene.

They use spruce or cedar

because those woods are
lightweight and vibrate well.

Using a 30-ton press that
works like a cookie cutter,

they punch out the
shape of the guitar.

The size of the sound hole

affects how the
guitar will sound --

the larger the
hole, the more treble,

the smaller the
hole, the more bass.

Then they glue on a wood inlay
decoration called a rosette.

Next they make the
sides of the guitar.

They first immerse wood
pieces in boiling water

for about 15 seconds...

...then place them in a heated
press to make the curve.

The press applies heat from
both the top and the bottom

for about a minute.

Then they connect the two sides

with blocks of wood made
of either mahogany or poplar.

One is glued and clamped at
the bottom, the other at the top.

Then they glue on and
clamp a wooden lining

which will connect the
sides to the top and back.

Those little cuts give it
flexibility around the curves.

Then with a hand router,

they carefully notch the lining
to receive four wooden braces

to support the
back of the guitar.

Strategically placed braces
help the top of the guitar

withstand the
tension of the strings.

They also equalize
sound frequencies

by controlling vibration
differently at different spots.

After a vacuum press makes
the bracing adhere evenly,

they glue on the top and bottom.

The body of the guitar
is now assembled.

It goes into a press, then a
drying rack for several hours.

Next they glue
on a plastic binding

to protect the guitar's edges.

Then comes a fine sanding.

Next a machine with
a special sensor

measures the precise angle

at which the body
and neck of the guitar

will later be attached.

The angle is critical
for sound quality.

It drills the holes and
sands the pieces accordingly.

Next they apply lacquer --

four to eight coats,
depending on the finish.

The fingerboard is made
of rosewood or ebony.

The metal frets separate the
halftones on the musical scale.

An adjustable rod
goes inside the neck.

This lets the neck adapt
to the different tensions

that different types
of strings require.

They glue the
fingerboard on the neck...

...then vacuum-press it to
make sure it adheres evenly.

Next they install
the machine heads

on which the
strings will be wound.

The rod in the neck slips
into a groove on the body.

The neck is then bolted and
clamped until the glue dries.

Next they glue on the bridge,

securing it with temporary
screws and a clamp.

Then they glue on
the headstock nut,

a hard, plastic piece that
spaces the strings evenly.

Next comes the saddle,
then the bridge pins,

which lock the
strings in the bridge.

Finally they string the
guitar using an electric winder.

Because of all the
glue-drying time,

it takes three weeks
to make a guitar.

The wood will become suppler
the more the guitar is played,

so as the guitar ages,
the better it will sound.

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