The Secret Life of Machines (1988) s01e05 Episode Script
The Refrigerator
[Door opens, footsteps.]
[Creak!.]
[THUD!.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[vacuum cleaner noise.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[TV static noise.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[Steam hisses.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[sewing machine rattles.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[Whoop!.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
Tim: Most people take their fridges for granted, but life would be very different without them.
Probably the earliest record of artificial cooling comes from ancient Egypt where there are records of slaves being employed to fan earthenware pots.
That was the same idea as this the earthenware milk cooler.
You put water in the dish down below and and that keeps this cover wet And it's the evaporation of the water that cools the milk inside.
[howling winds.]
[axe chips out ice.]
Tim: The other method of cooling things, used extensively in ancient Rome, was simply to collect snow.
Using a bit of insulation, it can last a surprisingly long time without melting.
[howling wind.]
[horse and cart clip clop etc.]
[chattering laughing socialising people.]
[Wheeeeee noise.]
[Socialising continues.]
The Romans not only cooled their wine, but they also made ice cream.
[slurp.]
By the 19th century various other liquids had been discovered that evaporated much faster than water - like alcohol.
If I dab some on my hand, the cooling effect is quite noticeable.
it's evaporating so fast that my hand's almost dry already.
And this produces even more rapid evaporation.
it had been discovered, that various gases, when they're compressed can condense into liquids.
And in fact the, this is carbon dioxide in this cylinder.
And under pressure it's actually a liquid at room temperature.
If I open the valve it'll shoot out of this pipe and evaporate very rapidly back to a gas and the cooling effect is quite dramatic [hiss of high pressure gas.]
[hissing stops.]
You can see the black pipe has gone all white because it's covered in frost.
If this gas was collected and compressed again it could be condensed back to a liquid and a sort of cycle could be established.
[whirring noise.]
And this is exactly the principle of the modern fridge: The liquid under pressure escapes through the restriction valve, as it evaporates to a gas the pipes get very cold.
The gas is piped back to a pump where it gets compressed and heated.
The hot gas then cools, and condenses back to a liquid, still under pressure.
The cycle then starts all over again.
The first patent for a machine like this was granted in 1834, to Jacob Perkins At the time, Perkins' invention was not greeted with much interest, because there was already a well-established natural ice industry.
[running water.]
[Sawing ice.]
Ice was cut from the lakes in America on a vast scale.
[running water.]
[sawing ice.]
By 1890, it was harvesting 25 million tons a year.
Britain imported over half a million tons, partly from America and partly from Norway.
It was stored in giant wooden ice-houses, where it could last all summer.
This ice was delivered twice a week, by the ice men.
they put it into these domestic ice-boxes.
[thunking of ice.]
The ice went in the top, and the food goes in the bottom.
The ice slowly melted and ended up in a drip tray which had to be emptied every day or two.
Well, the natural ice industry was well established in Europe and in America, but in Australia the winters weren't really cold enough to produce much ice.
[Digeridoo.]
In 1837, James Harrison emigrated from Glasgow to Australia.
He became a journalist, but his real obsession was refrigeration.
Harrison: Och dear, I cannae concentrate, it's too hot If only I had a wee machine to make ice! Aye! [noisy machine.]
Tim: His first machine didn't work, which he blamed on inferior colonial workmanship.
He then went to England and persuaded a Dr.
Seeby to make one, based on Perkins' design.
By 1858 Harrision had brought Seeby's machine back to Australia.
Harrison: Here's mae machine.
And here you see, a perrfect lump of ice.
Crowd: Hurray! Harrison: Aye, there's a flywheel, and make sure Man: Okay Tim: Harrison was then commissioned by a brewery to build a commercial refrigeration plant.
So cooling Australian lager was the first practical use of an artificial refrigeration machine in the world.
Men: Okay, okay .
Ahhh! [beer cans rattle.]
[ring pull clinks.]
[loud machine noise.]
Ice factories soon opened up in England, in competition with the natural ice warehouses.
The Lowestoft Ice Company was one of the first, as David Forster remembers.
David: The ice company originally began in 1898 and it was my great grandfather, a Mr W.
F.
Cockerel, who decided that ordinary ice from the glaciers, the Norwegian glaciers, wasn't sufficient for good quality ice, so he decided to make artificial ice using ammonia refrigerant, which happened to come on the market in the 1870s, 1890s.
[loud rushing water.]
Tim: Water is placed in the ice molds, which are then lowered into the giant brine tank.
The circulating brine is cooled by pipes, full of the ammonia refrigerant, to about -10 C.
[noise of machinery.]
The brine tank is vast, the size of a public swimming pool.
[squeaky wheels.]
After a few days the water in the moulds has fully frozen, and ready for use.
To extract the ice, the moulds are first transferred to a bath of warm water to loosen them.
[water.]
[clanging.]
Although this process looks very impressive, today there are much quicker and cheaper methods of making ice.
Block ice is now really obsolete, and this is actually the last lift.
[clanking of ice.]
David: It's rather sad to see the last lift, that's on the floor there.
Tim: These are the last blocks? David: These are the last blocks.
David: Actually the very last blocks.
It's a very old fashioned way of making ice, and it's not really very viable nowadays.
[clanking of ice.]
[humming engine noise.]
This is the engine room of the ice factory, and it's, er, basically a series of large motors and compressors, where the ammonia is compressed, that provides the refrigeration to cool the brine tanks.
The modern domestic refrigerator is exactly the same in principle.
With an electric motor, and a compressor, obviously much smaller.
But there was a gap of about 30 years, between developing these large ones and making something that was practical enough to put in a kitchen.
These have quite a few problems, they leak, their glands and valves on them.
And also they're very smelly.
The whole place smells strongly of ammonia.
The General Electric Company of America decided that the best solution was to enclose the motor and the compressor in a single airtight container.
Their first model appeared in 1926.
And they advertised it as being "So utterly reliable, so utterly dependable, that we've been able to enclose all the moving parts in walls of steel.
And it is rather a handsome contraption.
The shape of this fridge was designed by the refrigeration engineers themselves.
Here it's being demonstrated by Bette Davis in 1935.
Woman: Morning! Bette: Good morning.
Woman: My dear, why didn't you wake me up? Bette: Oh there's nothing to do really.
Woman: And people quarrel with the inconvenience of living so far out? It's really been the most delightful weekend I've had in years.
Bette: I wouldn't live anywhere else.
Woman: Of course, that's the difficulty of service Tim: By the 1950s specialist industrial designers and stylists had been brought in.
They changed their fridges' appearance every year or so to keep in fashion, and to present a sophisticated image.
[slow music.]
And behind the separate refrigerator door, brand new for '57, scientifically planned illumination in the interior.
Not just one light, to light the upper area, but two to give full illumination across the top, and then a thid light, to light the lower shelf area.
Simply take the handy tray and place it in the ice ejector Then pull down on the handle.
That's all, no pushing, no shoving, simple, effortless.
The handle does all the work for you.
Ice cubes in a basket, just like that.
And cubes always stay separate and free from each other.
It's new, it's exclusive, for 1957.
And hows this for convenience? The new juice can dispenser that drops a new can in place as soon as you remove one.
And handy, as convenient, as the frozen food package dispenser alongside.
Remove one package and another is ready for instant use.
For more features to demonstrate, it's the Imperial 121 for 1957! [music builds up and ends.]
Tim: The modern fridge really is exactly the same as this one.
It looks a bit different because the pipes and the motor and the compressor are now rather more discretely put at the back of the fridge, the motor down here and the pipes up the top.
Here we've cut the pipework circuit out of a modern fridge This is the ice-box which is also the evaporator coil.
Pressed out of two sheets of aluminium.
This is the sealed unit that contains the motor and compressor.
And the hot gas comes out here and it it cooled and condensed back to a liquid in these pipes at the back.
Well, you can't actually see what's going on inside the evaporator, so Rex and I built this model which we've replaced the evaporator by this glass jar This is the liquid going into the evaporator here.
[dripping liquid.]
And it's evaporating inside the jar And returning to the, returning to the compressor as a gas I can feel the jar getting cold, and the coils at the back are getting quite hot.
The flow is controlled by this valve, just like the valve on the carbon dioxide cylinder.
And in fact early fridges had valves just like that.
But we've been having great trouble to get the setting on the valve right, it tends to freeze up completely.
In modern fridges the valve has been replaced by a fine capillary tube.
This has the same effect of restricting the flow.
And to stop it freezing up, the tube runs up alongside the warmed gas coming back down again, into the compressor.
Various gases have been tried as refrigerants, but most were too toxic, corrosive or inflammable.
Carbon dioxide itself is nearly ideal, but it has a rather strange property; it changes, it sometimes can change directly from a gas to a solid.
Which I think we can show you with this setup here.
Erm, If we [clanking.]
Turn it on [clank.]
[roaring noise.]
[inaudible.]
This so-called dry ice is very useful stuff.
It's used for keeping things cold, and it's also used theatrically, for creating effects of mist.
When it's usually put into hot water.
But it wouldn't be any good as a refrigerant, because the solid could keep blocking up the pipes.
Today most refrigerants are fluorocarbons, these are the same as the chemicals that are used as propellants in aerosol cans.
[crunching noise.]
They're ideal, except for the hole they're making in the ozone layer.
There are only a few ounces in each fridge, but there are a lot of fridges in the world, and all the fluorocarbon escapes whenever a fridge is scrapped.
We've cut the weld off this sealed unit so you can see what's inside.
Most of it is really the motor.
It all sits on these three springs which reduce the noise.
It sits in a puddle of oil, so even on an old fridge the whole thing looks almost brand new.
Outside, the motor is connected to a bit of electrical gear.
There's one device which gives the motor an extra kick to start it up, and another device to stop it if it gets too hot.
The compressor itself is really a little tiny lump that fits on the end.
If I turn the motor round, I think you can see the piston going up and down.
It's all very solidly made, because in the life of the fridge it goes round several thousand million times.
Inside there are too reed valves which let the refrigerant in one side, and out the other.
[motor whines.]
On this model, if we start it up, start the compressor going [motor.]
You can see the piston flies up and down at a fair rate, and the refrigerant comes in one side, and is pushed out the other side.
[motor.]
Fridge compressors have a variety of other uses they're often used for, as compressors for air brushes, and they're even used by dentists sometimes connected to the pipe that sucks the saliva out of your mouth.
Compressors and compressed air actually have all sorts of uses.
[click.]
[bang.]
[hiss.]
Rex: This capsule gun works entirely on compressed air I made it, a few years ago, to simulate bullet hits for a films and TV.
It's by necessity a bit complicated, the mechanism inside is a real plumber's nightmare.
Here you've actually got a reciprocating cylinder, which actually drives the bolt forwards and backwards.
When the charge, the capsule is put inside the breech, and it goes to the full extremity forward, it fires [hiss.]
compressed air down the barrel.
It fires, many types of capsule.
This one is a blood capsule and it would simulate a blood hit [hiss.]
and of course these little fellows which are actually explosive capsules and they give a shower of sparks, and a mild explosion when they hit.
[hiss-BANG!.]
Tim: Meanwhile back inside the fridge, the compressor is pumping the refrigerant round, but it still needs something to turn it on and off at the right temperature.
It does this with this fine tube full of a liquid.
The liquid expands as the temperature rises and that pushes out this small bellows at the end.
[click.]
[click.]
I've got one of these thermostat switches set up on the, this model here.
If I hold the end to raise the temperature, um, the bellows will expand, and at some point the contacts on top will flick over and the compressor will start up.
[clears throat.]
sometimes takes a little while.
(mutters) Perhaps it's not going to do it? [click.]
[motor.]
Ahhh! Well of course the thermostat switch also has a dial on it, to adjust the temperature that the compressor come on.
It does this by moving the contact arm.
The closer the arm to the bellows, the less the bellows has to expand to flick the switch.
[click.]
Thermostat switches have hundreds of uses.
Wherever something needs turning on or off at a particular temperature.
[clink clang.]
This is a water clock I built a few years ago with a friend.
On the hour, water is released from a tank on the roof, and this starts it all working.
[running water.]
It was important to stop the water freezing on the way down, so we fitted this thermostat to turn everything off whenever the temperature falls too low.
[clanging and running water.]
That completes the basic fridge mechanism, but without a thick layer of insulation, all the cold would quickly be lost.
This fridge has a blanket of fibreglass, just like roof insulation.
Old fridges used to have massive door handles and massive hinges, that could apply a large closing force.
And this squashed the rubber seal, all round the door, into contact with the frame.
To apply enough force, the whole fridge had to be very strongly made.
Voiceover: An elephant, weighing over 4 tons, wants to stand on top of this new fridgidaire.
And it must not show any signs of strain under this tremendous load! Will it take it? Can this new fridgidaire stand up under such terrific punishment? Those were the questions that flashed through everyone's mind.
But Look! Our elephant isn't in doubt.
And as he cautiously but firmly places each foot on top of the frigidaire it is proved, without a question of doubt, that this new frigidaire cabinet is a real masterpiece of construction.
Yes gentlemen, here is a cabinet so sturdy, so strong that the door can be opened and closed, while it supports this tremendous load of over 4 tons.
Tim: In modern fridges, there's a flexible magnetic strip inside the rubber seal.
You can sometimes see the seal pulling itself against the door frame, just after you've closed the fridge.
Here we've cut one of these seals out of a modern fridge.
And I can pull the magnetic strip out And just to prove it's magnetic [rattle.]
This has made it unnecessary for fridges to have such massive handles and hinges.
In fact, the whole casing can now be much less substantial.
Rex: When I was repairing domestic appliances for a living, one of the most common faults I'd come across on fridges, was the ill fitting door seal.
There's an easy way to check whether the door seal is actually gripping the cabinet or not, and that's to drop in a piece of paper Which should be quite a tight, locked, fit.
Here as you can see, there's a gap.
Now there's quite an easy way of repairing this, which was rather embarrassing when you was in a customer's house, because the first thing to do, was to get the customer out of the kitchen.
Because the only way to repair it satisfactorily was brute force.
So you used to very subtly ask them for the guarantee or something like that, so she went away to look at it, and then you repaired it, by merely putting your foot against the bottom and pulling like blazes [clunk.]
And you'll find that the door then fits.
As you can see that's gripped.
And of course, most people wouldn't like things like that done to their refrigerator.
Tim: The most inadequate and flimsy parts of a modern fridge must be the doors: The plastic cracks up The bottle stays pop out [cluck clank.]
And the ice-box door has to take an immense strain every time you try and open it when the thing's iced up! [clank snap!.]
In fact, I suspect that broken doors are the most common reason why fridges are thrown away.
But perhaps I'm being too critical.
A recent Which survey found that fridges were about the most reliable of our household machines.
And certainly every single one of the fridges that we got for this programme, from the scrap yard, was still in working condition.
It has been said that the weakest part of all machines, and computers, is their interface with the outside world.
And the idea of enclosing all the moving parts of a fridge as a single airtight unit has not only stopped all the leaks, but it's also produced a machine that has a quite unusual degree of reliability.
Just think how many times a year, your fridge has to turn on and off.
The front of your fridge may be cheap and nasty, but I hope the next time you look at the back of your fridge, you'll regard it with suitable admiration.
[Jazzy music: 'Take 5' - Dave Brubeck.]
[Creak!.]
[THUD!.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[vacuum cleaner noise.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[TV static noise.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[Steam hisses.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[sewing machine rattles.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
[Whoop!.]
[Jazzy music: 'The Russians Are Coming' - Val Bennett.]
Tim: Most people take their fridges for granted, but life would be very different without them.
Probably the earliest record of artificial cooling comes from ancient Egypt where there are records of slaves being employed to fan earthenware pots.
That was the same idea as this the earthenware milk cooler.
You put water in the dish down below and and that keeps this cover wet And it's the evaporation of the water that cools the milk inside.
[howling winds.]
[axe chips out ice.]
Tim: The other method of cooling things, used extensively in ancient Rome, was simply to collect snow.
Using a bit of insulation, it can last a surprisingly long time without melting.
[howling wind.]
[horse and cart clip clop etc.]
[chattering laughing socialising people.]
[Wheeeeee noise.]
[Socialising continues.]
The Romans not only cooled their wine, but they also made ice cream.
[slurp.]
By the 19th century various other liquids had been discovered that evaporated much faster than water - like alcohol.
If I dab some on my hand, the cooling effect is quite noticeable.
it's evaporating so fast that my hand's almost dry already.
And this produces even more rapid evaporation.
it had been discovered, that various gases, when they're compressed can condense into liquids.
And in fact the, this is carbon dioxide in this cylinder.
And under pressure it's actually a liquid at room temperature.
If I open the valve it'll shoot out of this pipe and evaporate very rapidly back to a gas and the cooling effect is quite dramatic [hiss of high pressure gas.]
[hissing stops.]
You can see the black pipe has gone all white because it's covered in frost.
If this gas was collected and compressed again it could be condensed back to a liquid and a sort of cycle could be established.
[whirring noise.]
And this is exactly the principle of the modern fridge: The liquid under pressure escapes through the restriction valve, as it evaporates to a gas the pipes get very cold.
The gas is piped back to a pump where it gets compressed and heated.
The hot gas then cools, and condenses back to a liquid, still under pressure.
The cycle then starts all over again.
The first patent for a machine like this was granted in 1834, to Jacob Perkins At the time, Perkins' invention was not greeted with much interest, because there was already a well-established natural ice industry.
[running water.]
[Sawing ice.]
Ice was cut from the lakes in America on a vast scale.
[running water.]
[sawing ice.]
By 1890, it was harvesting 25 million tons a year.
Britain imported over half a million tons, partly from America and partly from Norway.
It was stored in giant wooden ice-houses, where it could last all summer.
This ice was delivered twice a week, by the ice men.
they put it into these domestic ice-boxes.
[thunking of ice.]
The ice went in the top, and the food goes in the bottom.
The ice slowly melted and ended up in a drip tray which had to be emptied every day or two.
Well, the natural ice industry was well established in Europe and in America, but in Australia the winters weren't really cold enough to produce much ice.
[Digeridoo.]
In 1837, James Harrison emigrated from Glasgow to Australia.
He became a journalist, but his real obsession was refrigeration.
Harrison: Och dear, I cannae concentrate, it's too hot If only I had a wee machine to make ice! Aye! [noisy machine.]
Tim: His first machine didn't work, which he blamed on inferior colonial workmanship.
He then went to England and persuaded a Dr.
Seeby to make one, based on Perkins' design.
By 1858 Harrision had brought Seeby's machine back to Australia.
Harrison: Here's mae machine.
And here you see, a perrfect lump of ice.
Crowd: Hurray! Harrison: Aye, there's a flywheel, and make sure Man: Okay Tim: Harrison was then commissioned by a brewery to build a commercial refrigeration plant.
So cooling Australian lager was the first practical use of an artificial refrigeration machine in the world.
Men: Okay, okay .
Ahhh! [beer cans rattle.]
[ring pull clinks.]
[loud machine noise.]
Ice factories soon opened up in England, in competition with the natural ice warehouses.
The Lowestoft Ice Company was one of the first, as David Forster remembers.
David: The ice company originally began in 1898 and it was my great grandfather, a Mr W.
F.
Cockerel, who decided that ordinary ice from the glaciers, the Norwegian glaciers, wasn't sufficient for good quality ice, so he decided to make artificial ice using ammonia refrigerant, which happened to come on the market in the 1870s, 1890s.
[loud rushing water.]
Tim: Water is placed in the ice molds, which are then lowered into the giant brine tank.
The circulating brine is cooled by pipes, full of the ammonia refrigerant, to about -10 C.
[noise of machinery.]
The brine tank is vast, the size of a public swimming pool.
[squeaky wheels.]
After a few days the water in the moulds has fully frozen, and ready for use.
To extract the ice, the moulds are first transferred to a bath of warm water to loosen them.
[water.]
[clanging.]
Although this process looks very impressive, today there are much quicker and cheaper methods of making ice.
Block ice is now really obsolete, and this is actually the last lift.
[clanking of ice.]
David: It's rather sad to see the last lift, that's on the floor there.
Tim: These are the last blocks? David: These are the last blocks.
David: Actually the very last blocks.
It's a very old fashioned way of making ice, and it's not really very viable nowadays.
[clanking of ice.]
[humming engine noise.]
This is the engine room of the ice factory, and it's, er, basically a series of large motors and compressors, where the ammonia is compressed, that provides the refrigeration to cool the brine tanks.
The modern domestic refrigerator is exactly the same in principle.
With an electric motor, and a compressor, obviously much smaller.
But there was a gap of about 30 years, between developing these large ones and making something that was practical enough to put in a kitchen.
These have quite a few problems, they leak, their glands and valves on them.
And also they're very smelly.
The whole place smells strongly of ammonia.
The General Electric Company of America decided that the best solution was to enclose the motor and the compressor in a single airtight container.
Their first model appeared in 1926.
And they advertised it as being "So utterly reliable, so utterly dependable, that we've been able to enclose all the moving parts in walls of steel.
And it is rather a handsome contraption.
The shape of this fridge was designed by the refrigeration engineers themselves.
Here it's being demonstrated by Bette Davis in 1935.
Woman: Morning! Bette: Good morning.
Woman: My dear, why didn't you wake me up? Bette: Oh there's nothing to do really.
Woman: And people quarrel with the inconvenience of living so far out? It's really been the most delightful weekend I've had in years.
Bette: I wouldn't live anywhere else.
Woman: Of course, that's the difficulty of service Tim: By the 1950s specialist industrial designers and stylists had been brought in.
They changed their fridges' appearance every year or so to keep in fashion, and to present a sophisticated image.
[slow music.]
And behind the separate refrigerator door, brand new for '57, scientifically planned illumination in the interior.
Not just one light, to light the upper area, but two to give full illumination across the top, and then a thid light, to light the lower shelf area.
Simply take the handy tray and place it in the ice ejector Then pull down on the handle.
That's all, no pushing, no shoving, simple, effortless.
The handle does all the work for you.
Ice cubes in a basket, just like that.
And cubes always stay separate and free from each other.
It's new, it's exclusive, for 1957.
And hows this for convenience? The new juice can dispenser that drops a new can in place as soon as you remove one.
And handy, as convenient, as the frozen food package dispenser alongside.
Remove one package and another is ready for instant use.
For more features to demonstrate, it's the Imperial 121 for 1957! [music builds up and ends.]
Tim: The modern fridge really is exactly the same as this one.
It looks a bit different because the pipes and the motor and the compressor are now rather more discretely put at the back of the fridge, the motor down here and the pipes up the top.
Here we've cut the pipework circuit out of a modern fridge This is the ice-box which is also the evaporator coil.
Pressed out of two sheets of aluminium.
This is the sealed unit that contains the motor and compressor.
And the hot gas comes out here and it it cooled and condensed back to a liquid in these pipes at the back.
Well, you can't actually see what's going on inside the evaporator, so Rex and I built this model which we've replaced the evaporator by this glass jar This is the liquid going into the evaporator here.
[dripping liquid.]
And it's evaporating inside the jar And returning to the, returning to the compressor as a gas I can feel the jar getting cold, and the coils at the back are getting quite hot.
The flow is controlled by this valve, just like the valve on the carbon dioxide cylinder.
And in fact early fridges had valves just like that.
But we've been having great trouble to get the setting on the valve right, it tends to freeze up completely.
In modern fridges the valve has been replaced by a fine capillary tube.
This has the same effect of restricting the flow.
And to stop it freezing up, the tube runs up alongside the warmed gas coming back down again, into the compressor.
Various gases have been tried as refrigerants, but most were too toxic, corrosive or inflammable.
Carbon dioxide itself is nearly ideal, but it has a rather strange property; it changes, it sometimes can change directly from a gas to a solid.
Which I think we can show you with this setup here.
Erm, If we [clanking.]
Turn it on [clank.]
[roaring noise.]
[inaudible.]
This so-called dry ice is very useful stuff.
It's used for keeping things cold, and it's also used theatrically, for creating effects of mist.
When it's usually put into hot water.
But it wouldn't be any good as a refrigerant, because the solid could keep blocking up the pipes.
Today most refrigerants are fluorocarbons, these are the same as the chemicals that are used as propellants in aerosol cans.
[crunching noise.]
They're ideal, except for the hole they're making in the ozone layer.
There are only a few ounces in each fridge, but there are a lot of fridges in the world, and all the fluorocarbon escapes whenever a fridge is scrapped.
We've cut the weld off this sealed unit so you can see what's inside.
Most of it is really the motor.
It all sits on these three springs which reduce the noise.
It sits in a puddle of oil, so even on an old fridge the whole thing looks almost brand new.
Outside, the motor is connected to a bit of electrical gear.
There's one device which gives the motor an extra kick to start it up, and another device to stop it if it gets too hot.
The compressor itself is really a little tiny lump that fits on the end.
If I turn the motor round, I think you can see the piston going up and down.
It's all very solidly made, because in the life of the fridge it goes round several thousand million times.
Inside there are too reed valves which let the refrigerant in one side, and out the other.
[motor whines.]
On this model, if we start it up, start the compressor going [motor.]
You can see the piston flies up and down at a fair rate, and the refrigerant comes in one side, and is pushed out the other side.
[motor.]
Fridge compressors have a variety of other uses they're often used for, as compressors for air brushes, and they're even used by dentists sometimes connected to the pipe that sucks the saliva out of your mouth.
Compressors and compressed air actually have all sorts of uses.
[click.]
[bang.]
[hiss.]
Rex: This capsule gun works entirely on compressed air I made it, a few years ago, to simulate bullet hits for a films and TV.
It's by necessity a bit complicated, the mechanism inside is a real plumber's nightmare.
Here you've actually got a reciprocating cylinder, which actually drives the bolt forwards and backwards.
When the charge, the capsule is put inside the breech, and it goes to the full extremity forward, it fires [hiss.]
compressed air down the barrel.
It fires, many types of capsule.
This one is a blood capsule and it would simulate a blood hit [hiss.]
and of course these little fellows which are actually explosive capsules and they give a shower of sparks, and a mild explosion when they hit.
[hiss-BANG!.]
Tim: Meanwhile back inside the fridge, the compressor is pumping the refrigerant round, but it still needs something to turn it on and off at the right temperature.
It does this with this fine tube full of a liquid.
The liquid expands as the temperature rises and that pushes out this small bellows at the end.
[click.]
[click.]
I've got one of these thermostat switches set up on the, this model here.
If I hold the end to raise the temperature, um, the bellows will expand, and at some point the contacts on top will flick over and the compressor will start up.
[clears throat.]
sometimes takes a little while.
(mutters) Perhaps it's not going to do it? [click.]
[motor.]
Ahhh! Well of course the thermostat switch also has a dial on it, to adjust the temperature that the compressor come on.
It does this by moving the contact arm.
The closer the arm to the bellows, the less the bellows has to expand to flick the switch.
[click.]
Thermostat switches have hundreds of uses.
Wherever something needs turning on or off at a particular temperature.
[clink clang.]
This is a water clock I built a few years ago with a friend.
On the hour, water is released from a tank on the roof, and this starts it all working.
[running water.]
It was important to stop the water freezing on the way down, so we fitted this thermostat to turn everything off whenever the temperature falls too low.
[clanging and running water.]
That completes the basic fridge mechanism, but without a thick layer of insulation, all the cold would quickly be lost.
This fridge has a blanket of fibreglass, just like roof insulation.
Old fridges used to have massive door handles and massive hinges, that could apply a large closing force.
And this squashed the rubber seal, all round the door, into contact with the frame.
To apply enough force, the whole fridge had to be very strongly made.
Voiceover: An elephant, weighing over 4 tons, wants to stand on top of this new fridgidaire.
And it must not show any signs of strain under this tremendous load! Will it take it? Can this new fridgidaire stand up under such terrific punishment? Those were the questions that flashed through everyone's mind.
But Look! Our elephant isn't in doubt.
And as he cautiously but firmly places each foot on top of the frigidaire it is proved, without a question of doubt, that this new frigidaire cabinet is a real masterpiece of construction.
Yes gentlemen, here is a cabinet so sturdy, so strong that the door can be opened and closed, while it supports this tremendous load of over 4 tons.
Tim: In modern fridges, there's a flexible magnetic strip inside the rubber seal.
You can sometimes see the seal pulling itself against the door frame, just after you've closed the fridge.
Here we've cut one of these seals out of a modern fridge.
And I can pull the magnetic strip out And just to prove it's magnetic [rattle.]
This has made it unnecessary for fridges to have such massive handles and hinges.
In fact, the whole casing can now be much less substantial.
Rex: When I was repairing domestic appliances for a living, one of the most common faults I'd come across on fridges, was the ill fitting door seal.
There's an easy way to check whether the door seal is actually gripping the cabinet or not, and that's to drop in a piece of paper Which should be quite a tight, locked, fit.
Here as you can see, there's a gap.
Now there's quite an easy way of repairing this, which was rather embarrassing when you was in a customer's house, because the first thing to do, was to get the customer out of the kitchen.
Because the only way to repair it satisfactorily was brute force.
So you used to very subtly ask them for the guarantee or something like that, so she went away to look at it, and then you repaired it, by merely putting your foot against the bottom and pulling like blazes [clunk.]
And you'll find that the door then fits.
As you can see that's gripped.
And of course, most people wouldn't like things like that done to their refrigerator.
Tim: The most inadequate and flimsy parts of a modern fridge must be the doors: The plastic cracks up The bottle stays pop out [cluck clank.]
And the ice-box door has to take an immense strain every time you try and open it when the thing's iced up! [clank snap!.]
In fact, I suspect that broken doors are the most common reason why fridges are thrown away.
But perhaps I'm being too critical.
A recent Which survey found that fridges were about the most reliable of our household machines.
And certainly every single one of the fridges that we got for this programme, from the scrap yard, was still in working condition.
It has been said that the weakest part of all machines, and computers, is their interface with the outside world.
And the idea of enclosing all the moving parts of a fridge as a single airtight unit has not only stopped all the leaks, but it's also produced a machine that has a quite unusual degree of reliability.
Just think how many times a year, your fridge has to turn on and off.
The front of your fridge may be cheap and nasty, but I hope the next time you look at the back of your fridge, you'll regard it with suitable admiration.
[Jazzy music: 'Take 5' - Dave Brubeck.]