21x13 - Car Tires, Silk, Art Conservation, Scuba Tanks

[bunniefuu]

Narrator: historically, wheels
were made of metal or wood.

With the invention
of air filled car tires

In the early part
of the 20th century,

The ride was revolutionized.

The inflated rubber tires

Could better absorb
the bumps on the road

And the addition of tread

Gave the invention
serious traction.

Car tires have come a long way
in the last century.

The modern summer tire
is made of



Which include
natural and synthetic rubber,

Chemical additives,
and carbon black -- a pigment.

Giant blenders
mix these ingredients

Under heat
and tremendous pressure.

There are various formulations
for different parts of the tire.

In each case, the result is
gummy rubber dough,

Which machinery
then rolls into sheets

To await further kneading
and processing.

Polyester fabric unrolls into
a machine called a calender.

The calender
is equipped with rollers

That apply warm rubber
to both sides of the fabric.

This produces
a rubberized fabric

That will be used
to reinforce the tire.

This fabric ply is needed
because rubber alone

Isn't sturdy enough
to make a tire.

Numerous cotton cords now
spin off bobbins simultaneously.

Machinery pulls them onto
the warm, rubberized fabric.

They land on a bit of an angle
and adhere.

This cording creates channels
that provide pathways

For venting air
during the actual tire building.

Making rubber for tread requires

Three different
rubber formulations.

Extruders shape
the three streams of rubber

And then they enter a die
that forms them into one.

Mini paint rollers apply
different colored stripes.

It's a coding system
for identification

Of the ingredients
during processing.

To avoid tension, the system
creates slack in the feed.

A blade slices the tread rubber
to length.

Next, many steel cables uncoil
at once to make the bead --

The part of the tire that gives
it the strength it needs

To stay on the wheel rim.

Machinery arranges the cables
in the desired configuration

And encases them in rubber.

More equipment rolls
the bead material into hoops

Sized to fit the wheel rim.

They're now
ready to build the tire.

Using a special rotating drum,

A worker arranges
the two bead hoops on it.

Next up is
an airtight piece of rubber

That will act as an inner tube
followed by the corded ply.

Inflated bladders
roll the rubber around the bead

On both sides and then retract.

A server
applies side walls to the beads.

Little rollers fold
the side walls over the beads.

This completes the inner part,
or skeleton, of the tire.

They assemble
the outer layer separately

Beginning with strips of rubber
embedded with steel cord.

The system wraps this rubber

Around a second
tire-building drum.

Next up
are narrow strips of rubber ply.

The computerized system
winds them

With just the right amount of
tension for a graduated effect.

They're now ready for
the last layer --

The tread rubber.

Machinery applies it to the ply.

It's time for the two
tire fabrications to become one.

A transfer ring
collects the assembly

And transfers it
to the inner part.

Compressed air inflates the tire
to shape it

And all the sticky layers
adhere together.

The machine rolls
the edge of the tread rubber

Over the side walls.

They now have what's known in
the industry as a green tire --

An uncured tire
without tread pattern.

Next, it's into a mold
to bake and shape the tire.

The two parts of the mold come
together like a waffle iron.

Inside, hot steamy bladders
expand to shape the tire

And transfer the tread pattern
to it.

This specific tread pattern
is designed for summer tires.

This cutout of a car tire
demonstrates

How all the layers
have been fused together.

The time
in the hot, pressurized mold

Has caused the
rubber to vulcanize --

A chemical reaction
that transforms it

From a weak and sticky substance

To one that's
strong and elastic.

A worker trims excess rubber.

After final inspections confirm

The tire shape is uniform
and geometrically correct,

The tire is ready for shipment.

It's time for the rubber
to hit the road.

Narrator:
silk fabric originated in china

At least 5,000 years ago

And became a coveted luxury.

Silk thread
is produced by silkworms

When they make their cocoons.

Sericulture,

Or commercially breeding
silkworms for silk production,

Is practiced
in several asian countries.

From home goods
to accessories and clothing,

There are few textiles
as elegant and luxurious,

Or as prized
throughout the ages, as silk.

It's hard to believe
this beautiful fabric

Comes from worms.

The female silkworm
lays up to 400 eggs in one shot

Then promptly dies.

Each egg, about two weeks later,
hatches into a larva.

The larva feeds on fresh
mulberry leaves continuously,

Increasing its body weight


And growing to a length
of about three inches.

Then, as it enters the
pupa phase of its life cycle,

It excretes liquid raw silk

From salivary glands
in its mouth.

When that liquid silk
contacts with the air,

It hardens into a single thread.

Pupating larva
winds that thread around itself

Into a thick, cozy cocoon.

Normally,
the pupa inside becomes a moth

And the cocoon
breaks as it emerges.

However, this severs
the continuous silk thread.

So to keep the thread intact,

They boil the cocoon
for about three minutes

To k*ll the pupa inside

Before it
transforms into a moth.

Boiling the cocoons also

Makes the wound thread
easier to unravel

By melting away
most of the sericin --

The gelatinous protein
that binds it.

To harvest the silk,
they take threads

From 30 to 50 cocoons at a time.

They feed them all together

Through a hole
in the bamboo stick

Onto a hand-operated reel.

Then, slowly and carefully,
they turn the reel,

Unraveling the cocoons.

As the thread passes together
through the stick,

The remaining sericin
glues them together

Forming a single,
thicker thread.

The silk threads coming together
are so fine --

Only about one one-hundredth
of a millimeter in diameter --

That it takes


To produce
a pound of silk thread.

Unraveling cocoons
is a time-consuming process,

Because a single thread
can be as long as

Nine professional soccer fields.

To make this feather-like
silk thread easier to handle,

They weigh it down with sand
before rolling it into a bundle.

Next, they wash away
the sand and remaining sericin,

Then bleach the thread
so it will uniformly absorb

The synthetic dye.

It's critical to monitor
the ratio of dye to hot water,

As well as water temperature
and soaking time,

As all these factors combined
effect the quality of the color.

After rinsing away the
excess dye with lukewarm water,

They hang the thread to dry.

They mount the bundles
of dry, dyed silk thread

On a big machine,

Which transfers them
to smaller rollers.

Those rollers then
go on an automated machine,

Which transfers the thread
to small bobbins.

To craft silk fabric,

Weavers will pass
bobbins of thread horizontally

Between vertical threads

On a traditional,
hand-operated loom.

Another machine, meanwhile,
winds thread around spools.

A worker then installs
a set number of spool threads

On a mechanism,

Which aligns them vertically
on the loom

Parallel to each other.

Fabric that's
about three feet wide

Typically requires


By stepping on
the loom's foot pedal,

The weaver repeatedly raises
every second vertical thread,

And with a tug of a cord,
passes a shuttle

Containing a bobbin of thread
horizontally in between.

This intertwining of
horizontal and vertical threads

Weaves the silk fabric.

To create a pattern, the weaver
uses multiple shuttles

Containing threads of different
colors, thicknesses,

And textures.

Some patters, such as an
intricate weave called brocade,

Are so intricate that even
the most experienced weavers

Produce just two to six inches
of fabric per day.

Now, that's wearable art.

Narrator:
a centuries-old painting
is actually

Easier to restore
than a decades-old painting.

For hundreds of years,
artists used pure oil paints,

But by the 20th century,

Artists began using
different types of paint,

Making restoration
more challenging.

A traditional painting
is typically oil on canvas,

Protected with a layer
of natural resin varnish.

Over time, a linen canvas
can become brittle,

Distort, and sometimes tear.

Varnish yellows
and dirt and dust accumulate,

Rendering the once-vibrant
painting dark and dull

And in dire need of
professional conservation.

The conservation process
is multi-faceted.

They have to strip away
any previous restoration,

Then perform a new restoration,

Yet make it entirely reversible
to allow for future restoration.

The conservators
begin with spot tests

To observe how
different colors in the painting

React to cleaning.

They dip a cotton swap
in mild detergent

And rub gently,

Testing for discolored varnish

And any previous restoration.

When all that's done,
they swab on some solvent

To neutralize
the detergent residue.

Next, they spray the back
of the canvas with water

And lie the painting
on a vacuum hot table.

The heat
turns the moisture to steam,

Which relaxes
the paint and linen

As the vacuum pulls
the bumps and puckers flat.

If the canvas
isn't structurally sound,

They apply adhesive,
a synthetic backing,

Then a new linen canvas.

With thermometers
monitoring the temperature,

The heat activates the adhesive

And the vacuum draws everything
taut against the hot table,

Bonding old linen to new.

And the conservators can turn
their attention to the artwork.

They begin by
mixing a cleaning solution --





And 79% water.

They dip a swab
in the cleaning solution

And another in the solvent.

Working a small area at a time,

They gently glide
the cleaning-solution swab

Over the surface.

It's critical not to rub,

As any abrasion
could harm the painting.

Next, they gently roll the
solvent swab over the same area

To neutralize
the cleaning-solution residue.

They repeat the solution-solvent
procedure area by area

Until they've removed surface
dirt from the entire painting.

Then they start all over again,

This time removing
old, yellowed varnish,

Embedded dirt,
and previous restoration.

The cleaning completed,

They can now address
the tears and damages.

Using a small pallet knife,

They fill the cavities
of the tear with gesso,

Material that's used
as a background for paintings.

This gesso is reversible,

Meaning it can
easily be removed, if required,

During a future restoration.

Once the gesso dries,

They wipe away the excess
with a damp cloth,

Leaving a repair that's flush
with the surrounding surface.

Then they
seal the gesso with varnish.

This creates a barrier
between the existing paint layer

And the one
they're about to add,

Making it removable
for future restoration.

They retouch the repaired area,

Expertly
matching colors to the original

And blending them seamlessly
with the surrounding area.

This process, called inpainting,

Is where the conservators'
fine-art training

Is put to the test.

Rather than use oil paints,

They mix pigments
with acrylic resin.

This produces paint
that looks just like oils

But is removable
with mild solvents

In the event of
a future restoration.

They brush varnish
over the inpainting

So that the sheen matches
that of the surrounding area.

And now, the final step.

They spray the entire painting

With a light coat of
removable synthetic varnish that

Doesn't yellow over time.

This evens out
and protects the surface.

Once the varnish cures,

The painting
goes back into its frame,

Just the way
the artist intended.

Narrator: underwater exploration
was a shallow experience

Until scuba tanks were developed

In the middle of
the 20th century.

Filled with compressed air

And attached to
a breathing regulator,

Scuba tanks enable divers
to stay underwater longer.

This invention took diving
to a whole new level.

Scuba tanks are a way to
bottle the air we breathe

And take it with us underwater.

To make aluminum scuba tanks,

They start with solid,
cylindrical chunks called slugs.

The aluminum-alloy slugs

Tumble around
in a perforated, rotating drum,

Which takes them through
a series of chemical baths.

The baths clean and treat
the surface of the aluminum

To prepare the slugs
for forming.

The operator loads
the slugs into a feeder system

That serves them up
one at a time

To a hydraulic extrusion press.

An extrusion piston
forces the slug

Into a die inside the press.

It hollows
and stretches the slug

Into the shape of a scuba tank.

It takes
about 1,300 tons of force

To transform
a solid, short chunk of aluminum

Into a longer, hollow cylinder.

The shaping process itself
generates heat,

Making the aluminum
softer and more malleable.

The press establishes
the outer diameter of the tank,

The inner one, and the base.

The process
takes just 20 seconds.

The freshly formed cylinder
now spins

As a roller applies a lubricant
to the open end.

The machine ejects the cylinder.

Then it's over to
the hydraulic neck press.

This press
forces the opening of the tank

Into a die
to narrow it substantially.

This establishes the basic shape
of the scuba-tank neck.

It still needs more work,

But first, the tank shape
must be firmed up.

They heat treat and then quench
the scuba tanks in cool water.

The shock of the rapid cooling
hardens the aluminum.

Back to the neck now.

A spinning, computerized cutter
shortens it.

Then, another cutter moves in.

Filings fly
as it carves excess metal

From the outside
of the scuba-tank neck.

A computerized drill
widens the neck hole

And cuts a pocket
for an o ring seal.

The next tool carves a thread

Into the inside wall
of the neck.

The threaded profile
will allow for connections

To an air-fill-up valve
and to a breathing regulator.

Every scuba tank
undergoes a test

To measure tank expansion
under pressure.

They fill each scuba tank
with water

And place it in a test jacket
that's also filled with water.

Testing equipment increases
the pressure in the scuba tank,

And the tank expands, placing
water from the test jacket.

By measuring
the displaced water,

They determine
the rate of tank expansion,

And if it's acceptable,
the tank moves on.

A scuba tank now
spins against a sanding belt.

This sanding gives the exterior
a brushed finish,

Which some divers prefer.

They etch the serial number
and other information

Onto the upper part of the tank.

For a more colorful look,
the factory applies

A vibrant, translucent powder
coat to the brushed finish.

The finish is purely aesthetic.

Aluminum doesn't rust,

So a natural finish would
weather underwater conditions

As well as the powder coat.

They bake on the powder coat,
giving the tanks a glossy look.

These aluminum scuba tanks are
now ready to take the pressure.

Life is sure to be

One underwater adventure
after another.