How It's Made (2001–…): Season 4, Episode 9 - Car Engines/Flour/Recliners/Envelopes - full transcript


CAPTIONS PAID FOR BY
DISCOVERY COMMUNICATIONS, INC.

Narrator:
TODAY ON "HOW IT'S MADE"...

...CAR ENGINES...

...FLOUR...

...RECLINERS...

...AND ENVELOPES.

CAR ENGINES WORK
BY INTERNAL COMBUSTION,

A PROCESS THAT HAPPENS IN EACH
OF THE ENGINE'S CYLINDERS.

AIR AND A DROP OF GASOLINE
ENTER THE CYLINDER.

THE PISTON MOVES UPWARD,
COMPRESSING THE MIXTURE.

THE SPARK PLUG
IGNITES THE GASOLINE

CAUSING AN EXPLOSION
THAT DRIVES THE PISTON DOWNWARD,

POWERING THE ENGINE.

ENGINE COMPONENTS ARE HOUSED IN
WHAT'S CALLED THE ENGINE BLOCK.

IT ARRIVES AT THIS PLANT
PARTIALLY MADE.

HERE, THEY FINISH IT OFF BY
MACHINING THE CYLINDER BORES,

THE HOLES IN WHICH
THE PISTONS MOVE UP AND DOWN.

THE TOOL
CARVES A CRISSCROSS PATTERN

ON THE CYLINDER BORE WALLS.

LUBRICATING OIL WILL CLING
TO THE GROOVES IN THIS PATTERN

ENABLING THE PISTONS
TO MOVE SMOOTHLY.

AFTER MACHINING,

THE ENGINE BLOCK
TRAVELS UPSIDE DOWN

TO THE ENGINE ASSEMBLY LINE.

WHEN IT ARRIVES THERE,

A SCANNER RECORDS
THE BLOCK'S TRACEABILITY CODE,

A BARCODE
THAT ENABLES THE FACTORY

TO TRACK THE BLOCK THROUGH
EVERY STAGE OF PRODUCTION.

AS THE ENGINE BLOCK
TRAVELS DOWN THE LINE,

ERROR-PROOFING DEVICES

ENSURE THAT EACH COMPONENT
IS INSTALLED PROPERLY.

ELSEWHERE IN THE FACTORY,

THE CRANKSHAFT
IS SLOWLY TAKING SHAPE.

THE CRANKSHAFT IS A BAR
THAT'S ROTATED

BY THE UP-AND-DOWN MOTION
OF THE PISTONS.

AS IT TURNS, IT TRANSFERS POWER
TO THE TRANSMISSION.

THE CRANKSHAFT STARTS OUT AS
A ROUGHLY SHAPED STEEL FORGING.

ROBOTIC ARMS
PASS IT DOWN THE LINE

FROM STATION TO STATION UNTIL,
20 TOOLING MACHINES LATER,

IT'S FULLY FORMED.

NOW THEY INSTALL
A STEEL DISC WITH TEETH

CALLED THE RELUCTOR RING.

THEY HEAT IT AND PRESS IT
ONTO THE CRANKSHAFT.

AS IT COOLS,
IT SHRINKS TO A TIGHT FIT.

THIS RING HELPS TIME
THE COMBUSTION CYCLE.

AS IT SPINS,

ITS TEETH
PASS IN FRONT OF A SENSOR,

WHICH READS
THE CRANKSHAFT'S POSITION

AND TELLS THE ENGINE
TO FIRE THE SPARK PLUGS

AT PRECISELY THE RIGHT MOMENT.

NOW THEY BALANCE
THE CRANKSHAFT.

IF IT'S OFF-KILTER,
THE ENGINE WILL VIBRATE.

A COMPUTER ANALYZES THE SPIN

AND DETERMINES WHETHER
THEY NEED TO DRILL OUT METAL

AT CERTAIN POINTS
TO ACHIEVE EQUILIBRIUM.

BACK ON THE ENGINE
ASSEMBLY LINE,

THE ENGINE BLOCKS
ARE STILL UPSIDE DOWN.

A ROBOT LUBRICATES
THE FOUR BEARINGS

ON WHICH THE CRANKSHAFT
WILL TURN,

THEN IT DROPS THE CRANKSHAFT
INTO POSITION.

THE PISTONS COME NEXT --

SIX PER ENGINE BECAUSE THESE
ARE SIX-CYLINDER ENGINES.

THE PISTONS ARE MADE
OF ALUMINUM.

ROBOTS INSTALL THEM
INTO THE CYLINDER BORES

OF THE ENGINE BLOCK.

A STEEL CONNECTING ROD ATTACHES
EACH PISTON TO THE CRANKSHAFT.

NOW WORKERS CAN CLOSE UP
THE BACK OF THE ENGINE BLOCK.

A ROBOT APPLIES SEALANT
TO THE REAR COVER.

THEY BOLT IT ON MANUALLY

WITH A TOOL CALLED
A MULTI-SPINDLE TORQUE GUN.

ON ANOTHER LINE,

THEY ASSEMBLE THE TWO HEADS

THAT'LL COVER THE TOP
OF THE ENGINE BLOCK.

THIS ROBOT IS APPLYING SEALANT
TO SPARK PLUG TUBES

BEFORE INSERTING THEM
INTO THE HEADS.

THE HEADS CAP OFF
THE CYLINDER BORES.

THEY PROVIDE EACH CYLINDER WITH
A SPARK PLUG AND FOUR VALVES --

TWO FOR ALLOWING
THE FUEL MIXTURE IN

AND TWO FOR RELEASING
THE EXHAUST.

THE BLACK TUBES RUNNING FRONT
TO BACK ARE THE CAM SHAFTS,

THE COMPONENTS THAT OPEN
AND CLOSE THOSE VALVES.

THERE ARE FOUR PER ENGINE.

A ROBOT APPLIES SEALANT

AND THEN BOLTS A COVER ONTO
THE FRONT OF THE ENGINE BLOCK,

THE HEAD, AND A COMPONENT
CALLED THE TIMING CHAIN.

THIS CHAIN CONNECTS THE
CRANKSHAFT TO THE CAM SHAFTS

SO THAT THEY ROTATE IN UNISON.

THIS ENSURES THE VALVES OPEN

WHEN THE PISTONS
ARE IN THE RIGHT POSITION.

FINALLY, THEY SPIN THE ENGINE
MECHANICALLY

TO MAKE SURE THE COMPONENTS
FUNCTION PROPERLY.

Narrator:
THE GRAIN MOST COMMONLY
GROUND INTO FLOUR IS WHEAT.

FLOUR MILLS USE HIGH-PROTEIN
OR HARD-WHEAT SPECIES

TO MAKE BREAD FLOUR

AND LOWER-PROTEIN
OR SOFT-WHEAT SPECIES

TO PRODUCE CAKE
AND PASTRY FLOUR.

ALL-PURPOSE FLOUR IS A
COMPROMISE WITH MEDIUM PROTEIN.

AS SOON AS THE WHEAT SHIPMENT
ARRIVES,

A GRAIN PROBE VACUUMS UP SAMPLES
FROM THROUGHOUT THE LOAD.

IF THE SAMPLES
PASS QUALITY INSPECTION,

THE MILL GIVES THE TRUCK
THE GO-AHEAD

TO DUMP THE WHEAT
ONTO AN UNDERGROUND CONVEYOR.

FROM THERE, THE GRAIN
GOES INTO A CLEANING MACHINE,

WHERE A SYSTEM OF SIEVES
REMOVES IMPURITIES

SUCH AS STRAW,
STICKS, AND GRAIN DUST.

THE WHEAT THEN GOES INTO STORAGE
SILOS UNTIL MILLING TIME.

THE PROTEIN CONTENT OF WHEAT
VARIES BY SPECIES,

SO THE FIRST STEP

IS TO BLEND TOGETHER
THE RIGHT VARIETIES OF WHEAT

FOR THE TYPE OF FLOUR
THEY'LL BE MAKING.

FROM THE BLENDER,

THE WHEAT GOES THROUGH A SECOND,
MORE INTENSIVE CLEANING SYSTEM

THAT REMOVES THE TINIEST
OF IMPURITIES,

SUCH AS WEED SEEDS AND DUST.

ON THE WAY
TO THE MILLING MACHINES,

A SCALE
TRACKS PRODUCTION QUANTITIES.

THIS MILL'S VERTICAL-PRODUCTION
LINE IS FIVE STORIES HIGH.

GRAVITY
CARRIES THE WHEAT DOWNWARD

THROUGH A SUCCESSION
OF MILLING MACHINES.

EACH ONE GRINDS THE GRAIN
BETWEEN STEEL ROLLERS

AND THEN SIFTS IT.

PARTICLES TOO LARGE
TO PASS THROUGH A SIEVE

CONTINUE DOWNWARD INTO THE NEXT
MILLING MACHINE AND SO ON.

BY THE TIME THE WHEAT
HITS THE LAST MACHINE,

ANYTHING
THAT'S NOT FULLY PROCESSED

GETS VACUUMED UP TO THE TOP
TO BEGIN THE CYCLE AGAIN.

MILLS MAKE WHITE FLOUR

BY GRINDING ONLY THE
WHEAT KERNEL'S SOFT INNER PART,

CALLED THE ENDOSPERM.

THIS REQUIRES REMOVING THE BRAN,
THE KERNEL'S HARD SKIN,

AND THE GERM, ITS SEED.

THAT SEPARATION BEGINS
AS SOON AS THE WHEAT KERNELS

ENTER THE VERY FIRST
MILLING MACHINE.

ROLLERS BREAK OFF
THE GERM AND BRAN

AND CRUSH THE ENDOSPERM
INTO PIECES CALLED SEMOLINA.

SIFTING REMOVES THE GERM
AND LOOSE BRAN PIECES,

BUT MUCH OF THE SEMOLINA REMAINS
COVERED IN BRAN PARTICLES.

SO BETWEEN EACH MILLING STATION
IS A PURIFIER,

A MACHINE THAT USES
CONTROLLED AIR CURRENTS

TO FLOAT THE LIGHTER BRAN
ABOVE THE HEAVIER SEMOLINA,

ENABLING SIEVES TO SEPARATE
THE TWO COMPONENTS.

THE SEMOLINA GOES THROUGH
REPEATED GRIND, SIFT,

AND PURIFY CYCLES
UNTIL IT'S COMPLETELY CLEAN.

ONLY THEN CAN IT BE
FINELY GROUND INTO FLOUR.

THE GROUND SEMOLINA PASSES
THROUGH A SERIES OF SIEVES.

THIS ENSURES IT DOESN'T LEAVE
THE FINAL MILLING MACHINE

UNTIL IT'S BEEN GROUND
TO THE RIGHT POWDERY TEXTURE.

THERE ARE THREE MAIN TYPES
OF WHITE-WHEAT FLOUR.

BREAD FLOUR HAS HIGH PROTEIN,

ENABLING DOUGH TO RISE WELL
AND BAKE TO A FIRM TEXTURE.

CAKE FLOUR HAS LOW PROTEIN,

WHICH PRODUCES
A CRUMBLY TEXTURE.

ALL-PURPOSE FLOUR
IS THE COMPROMISE --

ITS MEDIUM-PROTEIN CONTENT

MAKES IT SUITABLE FOR BAKING
BOTH BREAD AND CAKES.

BY THE END OF PRODUCTION,

THE FLOUR MILL HAS PRODUCED
THREE DISTINCT PRODUCTS --

BRAN, USED FOR ANIMAL FEED
AND BAKING...

...WHITE-WHEAT FLOUR...

AND WHEAT GERM
FOR THE HEALTH-FOOD MARKET.

LEFTOVER BY-PRODUCTS
GO INTO LIVESTOCK FEED.

IN THE MILL'S
QUALITY-CONTROL LAB,

THEY BAKE THE PRODUCT
FOR WHICH THE FLOUR IS DESIGNED

AND THEN EXAMINE ITS APPEARANCE,
TEXTURE, AND TASTE.

THEY USE SPECIALIZED EQUIPMENT
TO CALCULATE THE VOLUME,

THE DENSITY, PROTEIN,
AND MOISTURE CONTENTS.

WITH BAKED GOODS DESTINED FOR
RETAIL SALE, LIKE THESE COOKIES,

IT'S ESPECIALLY IMPORTANT
TO MEASURE THE DIMENSIONS.

IF DOUGH OVEREXPANDS,

THE COOKIES
WON'T FIT IN THEIR PACKAGE.

JUST PRIOR TO PACKAGING,

THE MILL ENRICHES
ITS WHITE FLOUR

WITH VITAMINS AND MINERALS.

THIS REPLACES THE VITAMINS
AND MINERALS LOST

WHEN THE MILLING PROCESS
REMOVED THE BRAN AND GERM.

THEY SHAKE THE BAGS
TO SETTLE THE FLOUR.

BAGGED FLOUR IN VARIOUS SIZES
GOES OUT TO SUPERMARKETS,

RESTAURANTS,
AND COMMERCIAL BAKERIES,

WHILE TANKER TRUNKS
SHIP BULK FLOUR

TO LARGE INDUSTRIAL BAKERIES.

Narrator:
THE FIRST RECLINING ARMCHAIR

WAS INTRODUCED BY
THE La-Z-Boy COMPANY IN 1928.

TODAY, MANY COMPANIES
MAKE MOTION FURNITURE,

AS THE INDUSTRY CALLS IT,

AND THE TERM "RECLINER" NO
LONGER REFERS TO JUST ARMCHAIRS.

YOU CAN BUY RECLINING COUCHES
AND EVEN RECLINING SECTIONALS.

THIS FACTORY MAKES
RECLINING CHAIRS AND COUCHES

IN BOTH FABRIC AND LEATHER.

THE FURNITURE CONSTRUCTION
IS THE SAME,

REGARDLESS OF THE MATERIAL,

BUT LEATHER UPHOLSTERY
REQUIRES A FEW EXTRA STEPS.

THEY BEGIN
BY INSPECTING THE HIDE,

MARKING SERIOUS DEFECTS
WITH ONE COLOR OF TAPE

AND MINOR IMPERFECTIONS
WITH ANOTHER.

A COMPUTER-PROGRAMMED
CUTTING MACHINE

SCANS AND REGISTERS
THE TAPE MARKINGS,

THEN AUTOMATICALLY CUTS AND
DISCARDS THE DEFECTIVE PARTS.

IT CUTS UPHOLSTERY PIECES
FOR HIDDEN AREAS,

SUCH AS THE UNDERSIDES
OF SEAT CUSHIONS,

FROM THE IMPERFECT LEATHER

AND VISIBLE PARTS
FROM FLAWLESS LEATHER.

ONCE ALL THE PIECES ARE CUT,

THEY SEW TOGETHER THE BACK,
SEAT, AND ARMS.

THEN, THEY STUFF
THE ARMS AND BACK.

THEY POSITION THE OPEN END
AGAINST A BLOWING MACHINE

THAT FILLS IT
WITH POLYESTER FIBER.

WORKERS WEIGH EACH PART
BEFORE AND AFTER FILLING.

THIS ENSURES THEY'VE BLOWN IN
THE RIGHT AMOUNT OF FIBER

AND THAT BOTH ARMS
HAVE EQUAL FILLING.

NEXT, THEY'LL FILL THE SEAT
WITH FOAM.

A COMPRESSION MACHINE
SQUEEZES IT,

THEN A WORKER SPRAYS ON
SILICONE LUBRICANT.

THIS ENABLES THE SEAT COVER
TO SLIDE ON EASILY.

FOAM IS MADE
OF A CHEMICAL MIXTURE,

THE FORMULATION OF WHICH
DETERMINES THE DENSITY --

THE HIGHER THE DENSITY,
THE HIGHER THE QUALITY.

ELSEWHERE IN THE FACTORY,

THEY CUT THE FRAME COMPONENTS
FROM PLYWOOD

USING A COMPUTER-GUIDED
BAND SAW.

THESE LONG PIECES
WILL FORM THE SEAT FRAME.

A 3-SEATER COUCH
HAS 3 SEPARATE FRAMES,

ENABLING EACH SEAT
TO RECLINE INDIVIDUALLY.

A MACHINE LINES ONE SIDE OF EACH
PIECE WITH STEEL SPRING CLIPS.

A WORKER THEN DABS THE ENDS IN
GLUE AND ASSEMBLES THE PIECES,

REINFORCING THEM
WITH LONG, GLUE-COATED STAPLES.

AS THE STAPLES ENTER THE WOOD,

FRICTION-GENERATED HEAT
MELTS THE GLUE.

THE GLUE THEN DRIES,
SECURING THE STAPLES.

NOW COMES THE STEP
KNOWN AS "SPRINGING THE SEAT."

THEY HOOK FIVE THICK, STEEL
SPRINGS INTO THE SPRING CLIPS,

THEN HAMMER THE CLIPS CLOSED
TO LOCK THE SPRINGS IN PLACE.

THEY CONNECT THE SPRINGS WITH
A PLASTIC-COVERED WIRE SO THAT,

WHEN YOU SIT ON THE SEAT,
ALL THE SPRINGS REACT IN UNISON.

THEY ASSEMBLE THE FRAME PIECES
FOR THE ARM,

USING GLUE
AND GLUE-COATED STAPLES,

PLUS A FEW SCREWS
AT STRATEGIC POINTS.

THEY SCREW THE ARM TO THE SEAT
AND BEGIN UPHOLSTERING.

FIRST, A LAYER OF FELT TO
CUSHION THE SPRINGS, THEN WOOD,

CARDBOARD, AND FOAM TO FORM THE
ROUNDED SHAPE OF THE ARMREST.

AFTER LUBRICATING
WITH SILICONE SPRAY,

THEY SLIP ON THE LEATHER
AND STAPLE IT IN PLACE.

THEY UPHOLSTER THE BACKREST
AND SIDES IN THE SAME MANNER.

THE RECLINING MECHANISM

ARRIVES AT THE FACTORY
WITH THE SIDES PREASSEMBLED.

WORKERS INSTALL
THE CONNECTING PIECES,

THEN A BUSHING THAT REDUCES
THE NOISE THE MECHANISM MAKES.

FINALLY, THEY INSTALL A SPRING
TO CONTROL THE RECLINE SPEED.

THEY SCREW THE MECHANISM
TO THE SEAT FRAME...

...THEN HOOK UP THE OPERATING
HANDLE AND TEST IT OUT.

TO COVER THE BACK
OF THE FURNITURE,

THEY ATTACH METAL TACKING STRIPS
TO THE LEATHER...

...THEN TURN THE EDGE UNDER AND
HAMMER THE TACKS INTO THE FRAME,

USING A PNEUMATIC HAMMER.

THE LAST STEP IS TO ATTACH
THE BACK TO THE SEAT.

THERE'S THE DETACHABLE FLAP
AT THE BOTTOM,

PROVIDING ACCESS
TO A LOCKING SPRING INSIDE.

THE LOCKING SPRING
LETS YOU REMOVE THE BACK

IF YOU HAVE TROUBLE GETTING
THE FURNITURE THROUGH A DOORWAY.

AT THIS FACTORY,

WORKERS ARE ENCOURAGED
TO LIE DOWN ON THE JOB,

BUT ONLY TO INSPECT
THE FURNITURE.

AFTER EXAMINING
THE FABRIC AND SEWING,

THEY ASSESS THE COMFORT
AND TEST THE RECLINING MOTION.

TALK ABOUT A CUSHY JOB.

Narrator: WE RIP IT OPEN
WITH BARELY A THOUGHT,

MORE ANXIOUS
TO READ ITS CONTENTS

THAN TO TAKE A MOMENT

TO TRULY APPRECIATE
ITS FORM AND FUNCTION,

AND THEN
WE RUTHLESSLY DISCARD IT.

THE HUMBLE ENVELOPE
JUST DOESN'T GET MUCH RESPECT

DESPITE ITS DISTINGUISHED
4,000-YEAR HISTORY.

AS EARLY AS 2,000 B.C.,

THE BABYLONIANS
BAKED SPECIAL CLAY WRAPPERS

TO TRANSPORT DOCUMENTS.

EVENTUALLY,

PEOPLE MADE ENVELOPES
FROM LIGHTER MATERIALS,

SUCH AS ANIMAL SKINS AND LEAVES.

BY ABOUT 1,000 A.D.,

IT BECAME THE CUSTOM
TO SIMPLY FOLD A LETTER

AND SEAL IT WITH A DROP OF WAX.

BUT EVERYTHING CHANGED IN 1837

WITH ENGLAND'S NEW
PENNY-POSTAGE SYSTEM.

TO MAIL A LETTER,

THE SENDER NOW HAD TO BUY
A POSTAGE-PAID PAPER WRAPPER

THAT FOLDED INTO AN ENVELOPE.

ONE OF THE MANY ENVELOPE STYLES
THIS FACTORY MAKES

IS A 12-BY-18-INCH ENVELOPE MADE
OF NATURAL-COLORED KRAFT PAPER.

A MACHINE, APPROPRIATELY CALLED
THE SHEETER,

CUTS THE ROLL
INTO 21-BY-25-INCH SHEETS.

A WORKER SELECTS THE CUTTING DIE
FOR THIS STYLE

AND INSTALLS IT
ON AN AUTOMATED PRESS.

AS EACH STACK OF SHEETS
PASSES UNDERNEATH,

THE PRESS APPLIES
11 TONS OF PRESSURE,

FORCING THE DIE RIGHT THROUGH
LIKE A GIANT COOKIE CUTTER.

THE SHAPED SHEETS
ARE CALLED "ENVELOPE BLANKS."

WORKERS NOW LOAD THE BLANKS

INTO THE FEEDER OF AN AUTOMATED
PIECE OF EQUIPMENT

CALLED A BLANK-SHEET
ENVELOPE-FOLDING MACHINE.

AS WE SEE HERE IN SLOW MOTION,

REVOLVING STEEL BLADES FIRST
MAKE SCORELINES, FOUR IN ALL --

ONE DOWN EACH SIDE, CREATING
THE ENVELOPE'S SIDE FLAPS,

ONE ACROSS THE TOP,
CREATING THE SEAL FLAP,

AND ONE ACROSS THE LOWER END,
CREATING THE BOTTOM FLAP.

FOLDING BLADES HOLD THE PAPER
DOWN ALONG THE SCORELINES,

WHILE ARMS PUSH UP
FROM UNDERNEATH,

FOLDING THE SIDE FLAPS
TOWARD THE CENTER.

JUST BEFORE THE FLAPS MEET,

THE MACHINE RUNS A LINE OF GLUE
DOWN THEIR EDGE.

THE FLAPS ADHERE TO EACH OTHER,
FORMING THE CENTER SEAM

THAT RUNS DOWN THE BACK
OF THE ENVELOPE.

THE MACHINE THEN GLUES THE
BOTTOM FLAP AND FOLDS IT CLOSED.

YOU CAN SEE IN SLOW MOTION

HOW IT ALSO APPLIES GLUE
TO THE SEAL FLAP AT THE TOP,

KEEPING THAT FLAP OPEN
SO THAT THE GLUE WILL DRY.

THE SENDER HAS TO JUST REMOISTEN
THE GLUE TO SEAL THE ENVELOPE.

THE FINISHED ENVELOPE
EXITS THE FOLDING MACHINE

AND ENTERS ANOTHER MACHINE
THAT COUNTS THEM

AND STACKS THEM UPRIGHT.

THIS MORE SOPHISTICATED
PIECE OF EQUIPMENT

IS CALLED A WEB-ROLL
ENVELOPE-FOLDING MACHINE.

THEY FEED THE ROLL OF PAPER
DIRECTLY INTO THE MACHINE

AND, AS WE SEE HERE
IN SLOW MOTION,

IT DOES EVERYTHING

FROM CUTTING, SCORING, FOLDING,
AND GLUING THE BLANKS

TO COUNTING
THE FINISHED ENVELOPES.

FOR THIS STYLE,

A DIE EVEN PUNCHES OUT
AN ADDRESS WINDOW

IN THE FRONT OF THE ENVELOPE.

THIS ALL-IN-ONE MACHINE

GOES THROUGH ALL THE STEPS
AT LIGHTNING SPEED --

20 ENVELOPES PER SECOND.

THE THIN, TRANSPARENT FILM
THAT COVERS THE ADDRESS WINDOW

IS USUALLY MADE
OF POLYPROPYLENE.

THE MACHINE CUTS IT TO SIZE
AND GLUES IT TO THE ENVELOPE.

THIS MACHINE
DOESN'T HAVE FOLDING BLADES

TO HOLD THE PAPER DOWN
ALONG THE SCORELINES.

INSTEAD, THE BLANKS ROLL THROUGH
A SERIES OF ROTATING CYLINDERS

WITH AIR HOLES.

A SUCTION SYSTEM VACUUMS
THE BLANK TO THE CYLINDER

WHILE THE OPERATION
IS BEING PERFORMED,

THEN RELEASES THE VACUUM

TO TRANSFER THE PAPER
TO THE NEXT CYLINDER,

WHERE IT'S VACUUMED ON FOR THE
DURATION OF THE NEXT OPERATION.

INTERNAL-MAIL ENVELOPES ARE
OPENED AND CLOSED REPEATEDLY,

SO THEY DON'T HAVE A
LICK-AND-STICK SEAL FLAP

LIKE REGULAR ENVELOPES DO.

AS WE SEE HERE IN SLOW MOTION,

AN AUTOMATED MACHINE
RIVETS A CARDBOARD BUTTON

TO THE BACK OF THE ENVELOPE.

AT THE SAME TIME,

IT RIVETS ANOTHER BUTTON, WITH
A PIECE OF STRING, TO THE FLAP.

ENVELOPE FACTORIES USE
MANY DIFFERENT TYPES OF PAPER,

FROM TOP-QUALITY VELLUM
TO KRAFT PAPER.

WITH PRINTING EQUIPMENT

INCORPORATED
RIGHT INTO THE FOLDING MACHINES,

THEY CAN PRINT RETURN ADDRESSES,
EVEN ELABORATE CUSTOM DESIGNS.

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