Stuff Matters

date Dec 21, 2018
authors Mark Miodownik
reading time 30 mins

This is a book essentially about material science, but through practical stories of history and how we use them today! Great to know some of the most used materials in the modern world of civilisation today.

History of human progress

Civilization and materials

We may like to think of ourselves as civilized, but that civilization is in large part bestowed by material wealth. Without this stuff, we would quickly be confronted by the same basic struggle for survival that animals are faced with.

Stone, Bronze, Iron, Steel…

The material world is not just a display of our technology and culture, it is part of us. We invented it, we made it, and in turn it makes us who we are. The fundamental importance of materials to us is apparent from the names we have used to categorize the stages of civilization — the Stone Age, Bronze Age, and Iron Age —with each new era of human existence being brought about by a new material. Steel was the defining material of the Victorian era, allowing engineers to give full rein to their dreams of creating suspension bridges, railways, steam engines, and passenger liners.


The twentieth century is often hailed as the Age of Silicon, after the breakthrough in materials science that ushered in the silicon chip and the information revolution.

Gradual accumulation of knowledge

This gradual accumulation of knowledge got us from the Stone Age to the twentieth century before any real appreciation of the structure of materials was understood. The importance of that empirical understanding of materials, encapsulated in such crafts as the blacksmith’s, remains: we know almost all of the materials in this book with our hands as well as our heads.

Theory and practical

Even in the nineteenth century, when we had an impressive theoretical understanding of astronomy, physics, and chemistry, the making of iron and steel on which our Industrial Revolution was based was achieved empirically — through intuitive guesswork, careful observation, and a huge slice of luck.


Metals and their properties

Metals are fundamentally different from these other materials because they can be hammered into shape: they flow, they are malleable. Not only that, they get stronger when you hit them; you can harden a blade just by hammering it. And you can reverse the process simply by putting metal in a fire and heating it up, which will cause it to get softer.

Melting point

The melting point of a metal is an indicator of how tightly the metal atoms are stuck together and so also affects how easily the dislocations move. Lead has a low melting point and so dislocations move with consummate ease, making it a very soft metal. Copper has a higher melting point and is stronger.

Copper tools

The making of copper tools initiated a spectacular growth in human technology, being instrumental in the birth of other technologies, cities, and the first great civilizations. The pyramids of Egypt are an example of what became possible once there were plentiful copper tools. Each block of stone in each pyramid was extracted from a mine and individually hand-carved using copper chisels.

Pure copper loses its sharpness fast

It is estimated that the copper chisels would have needed to be sharpened every few hammer blows in order for them to be useful. Copper is not ideal for razor blades for the same reason.

Alloys are stronger

Alloys tend to be stronger than pure metals for one very simple reason: the alloy atoms have a different size and chemistry from the host metal’s atoms, so when they sit inside the host crystal they cause all sorts of mechanical and electrical disturbances that add up to one crucial thing: they make it more difficult for dislocations to move.

Sapphire and Ruby

crystal of aluminum oxide is colorless if pure but becomes blue when it contains impurities of iron atoms: it is the gemstone called sapphire. Exactly the same aluminum oxide crystal containing impurities of chromium is the gem called ruby.


Steel, the alloy of iron and carbon, is even stronger than bronze, with ingredients that are much more plentiful: pretty much every bit of rock has some iron in it, and carbon is present in the fuel of any fire. Our ancestors didn’t realize that steel was an alloy—that carbon, in the form of charcoal, was not just a fuel to be used for heating and reshaping iron but could also get inside the iron crystals in the process.

Romans and steel

As well as their weapons and armor, among the few, smaller steel objects that they probably did take with them were novacili, an object that epitomized their civilized approach to life: the Roman razor blade. These novacili, and the barbers who wielded them, allowed the Romans to retreat clean-shaven, groomed in order to distinguish themselves from the savage hordes that had driven them out.

Steel and the knight

At a time when swords regularly snapped in battle, leaving a knight defenseless, it is easy to see why a high-quality steel sword wielded by a strong warrior came to represent the rule of civilization over chaos. The fact that the process of making steel was, necessarily, highly ritualized also helps to explain why this material came to be associated with magic.

Steel and the Samurai

By the fifteenth century AD the sword steel made by the samurai of Japan was the best the world had ever seen and remained preeminent for five hundred years until the advent of metallurgy as a science in the twentieth century.

Cast iron for infrastructure

No one could create stronger and harder steel than the samurai until the Industrial Revolution. When at this time European countries first started to build structures on a larger, more ambitious scale—such as railways, bridges, and ships—they used cast iron, because it could be made in large quantities and poured into molds. Unfortunately it was extremely prone to fracture under certain conditions.

How Steel became manufacturable and repeatable

He didn’t really understand why the process was successful sometimes and unsuccessful at others, but he continued to work on his technology, and with the help of the British metallurgist Robert Forester Mushet he adapted his technique. Rather than trying to remove the carbon until just the right amount was left, about 1 percent, Mushet suggested removing all the carbon and then adding 1 percent carbon back in. This worked and was repeatable.

Gillette and the steel razor

This was to be the democratization of shaving. His vision was to eliminate the need to sharpen the blade by making it so cheap that when it became blunt you could simply throw it away. In 1903 Gillette sold 51 razors and 168 blades. The following year, he sold 90,884 razors and 123,648 blades.

Birth of stainless steel

No one at the time knew why, so he proceeded by trial and error, melting steels and adding different ingredients in order to discover their effects. One day it was aluminum, the next it was nickel. Brearley made no progress. If a new specimen turned out not to be hard, he chucked it in the corner. His moment of genius came when after a month he walked through the lab and saw a bright glimmer in the pile of rusting specimens. Rather than ignoring it and going to the pub, he fished out this one specimen that had not rusted and realized its significance: he was holding the first piece of stainless steel the world had ever known.

How stainless steel works

Like some hugely polite guest, it reacts with the oxygen before the host iron atoms can do so, creating chromium oxide. Chromium oxide is a transparent, hard mineral that sticks extremely well to steel. In other words, it doesn’t flake off and you don’t know it is there. Instead it creates an invisible, chemically protective layer over the whole surface of the steel. What’s more, we now know that the protective layer is self-healing; when you scratch stainless steel, even though you break the protective barrier, it re-forms.

Stainless Steel and cutlery

For, in the end, Brearley did manage to create cutlery from stainless steel, and it’s the transparent protective layer of chromium oxide that makes the spoon tasteless, since your tongue never actually touches the metal and your saliva cannot react with it; it has meant that we are one of the first generations who have not had to taste our cutlery.


Information storage

Most people’s work involves plenty of paperwork: despite talk of a paperless office, this has never transpired, nor does it look likely to, such is our trust in this material as a store of information.

Yellowing of paper

Paper yellows with age for two reasons. If it is made from cheap, low-grade mechanical pulp, it will still contain some lignin. Lignin reacts with oxygen in the presence of light to create chromophores (meaning, literally, “color-carriers”), which turn the paper yellow as they increase in concentration.

Photography paper

My dad is still here to tell the tale, but one day there will only be the photograph to remind us of this moment in time — a material fact of history that contributes to our collective memory. Of course, photographs are not really unbiased, but then neither are memories.

From scroll to codex form of paper

The invention of paper, said to be one of the four great inventions of the Chinese, solved these problems, but it wasn’t until the Romans replaced the scroll with the codex—or, as we call it now, the book—that the material reached its full potential. That was two thousand years ago, and it is still a dominant form of the written word.

Paper vs book

It is the thinness of paper that proves to be one of its great advantages, allowing it the flexibility to survive continuous handling, but when stacked together in book form becoming stiff and strong—essentially a re-formed block of wood.

Concertina format

Other cultures achieved something similar with the concertina format—forming a stack by repeatedly folding one continuous sheet of paper in on itself—but the advantage of the codex, with its individual pages, is that many scribes could work on the same book at the same time, and after the invention of the printing press many copies of the same book could be created at the same time. As biology had already discovered, the speedy copying of information is the most effective way of preserving it.

Holding a crease with stiffness

There are very few materials as good: metal foils can hold a crease, but control of the crease is somewhat more difficult. Plastic sheeting doesn’t tend to hold a crease at all, unless it is very soft, in which case it lacks the rigidity (and formality) required of a good wrapping material. So it is its ability to hold a crease while remaining stiff that makes paper uniquely suited to this purpose.

Thin razor sharp paper cut

It turns out that the look and feel of popular glamour magazines require a combination of stiffness and low weight, which turns the paper into a cutting instrument. The paper is so thin that its edges have the sharpness of a razor.

Thicker paper

When the thickness of paper is increased it loses its flexibility, becoming stiffer and stiffer until at some point it is stiff enough to hold itself up and not bend under its own weight. At this point it takes on new cultural roles, one of which is the permission to travel. Bus, train, and plane tickets the world over are made from thick paper called card.

From paper to digital

The world of travel is dominated by stiff, hard machines, and card reflects that back to us. Funnily enough, as cars and airplanes have gotten lighter and more efficient, so tickets have mirrored this, becoming thinner and thinner. Soon they will probably disappear altogether, becoming part of our digital lives.

E-Ink paper

Electronic paper is a type of flat screen that displays text using real ink and is designed to be read with reflective light bouncing off it in the same way as a physical book. The difference is that electronic paper can be controlled digitally to display any text required almost instantly. When integrated with a computer chip it can store and display millions of books.

Paper media vs digital media

For this reason, there is a sense in which they can be more easily manipulated, and that history itself could be altered. At the same time, it is precisely this immediacy and fluidity of content that makes the digital media so exciting.

Concrete - Fundamental

Concrete and water

concrete doesn’t dry out. Quite the opposite, water is an ingredient of concrete. When concrete sets, it is reacting with the water, initiating a chain of chemical reactions to form a complex microstructure deep within the material, so that this material, despite having a lot of water locked up inside it, is not just dry but waterproof.

Cement to Concrete

As the fibrils grow and meet, they mesh together, forming bonds and locking in more and more of the water, until the whole mass transforms from a gel to a solid rock. These fibrils will bond not only to each other but also to other rocks and stones, and this is how cement turns into concrete.

Ratio of water and cement is important

As with any chemical reaction, if you get the ratio of the ingredients wrong, then you get a mess. In the case of concrete, if you add too much water there won’t be enough calcium silicate from the cement powder to react with, and so water will be left over within the structure, which makes it weak. Similarly, if you add too little water there will be unreacted cement left over, which again weakens the structure.

Roman concrete engineering

The most impressive piece of Roman concrete engineering, however, is in its capital: the dome of the Pantheon in Rome. Still standing today, it is two thousand years old but still the largest unreinforced concrete dome in the world.

Reinforced concrete

Joseph’s solution was to embed loops of steel inside the concrete. He couldn’t have known that cement bonds very well to steel. It could easily have turned out that the steel was like the oil in the vinaigrette of concrete, preferring to keep to itself. But no, the calcium silicate fibrils inside concrete stick not just to stone but also to metal.

How is reinforced steel with concrete different?

Concrete reinforced with steel is fundamentally different: there is no naturally occurring material like it. When concrete reinforced with steel comes under bending stresses, the inner skeleton of steel soaks up the stress and protects it from the formation of large cracks. It is two materials in one, and it transforms concrete from a specialist material to the most multipurpose building material of all time.

Expansion and contraction

In other words, they expand and contract at almost the same rate. This is a minor miracle, and Joseph was not the only one to notice it. An Englishman, William Wilkinson, had also happened upon this magic combination of materials. Reinforced concrete’s time had come.

From decades to months…

This mechanization of the process of building is what makes concrete such a modern material. It lends itself to pouring and molding, to the rapid building of vast structures. The big structures of old, such as the stone cathedrals of Europe or the Great Wall of China, took decades to build. The central core of the Shard, one of the tallest buildings in Europe, took less than six months.

Why self-healing conrete is needed

Given that literally half of the world’s structures are made from concrete, the upkeep of concrete structures represents a huge and growing effort. To make matters more difficult, many of these structures are in environments that we don’t want to have to revisit on a regular basis, such as the Øresund Bridge connecting Sweden and Denmark, or the inner core of a nuclear power station. In these situations it would be ideal to find a way to allow concrete to look after itself, to engineer concrete to be self-healing. Such a concrete does now exist, and although it is in its infancy it has already been shown to work.

Self-healing conrete

Self-healing concrete has these bacteria embedded inside it along with a form of starch, which acts as food for the bacteria. Under normal circumstances these bacteria remain dormant, encased by the calcium silicate hydrate fibrils. But if a crack forms, the bacteria are released from their bonds, and in the presence of water they wake up and start to look around for food. They find the starch that has been added to the concrete, and this allows them to grow and replicate. In the process they excrete calcite, a form of calcium carbonate. This calcite bonds to the concrete and starts to build up a mineral structure that spans the crack, stopping further growth of the crack and sealing it up.

Chocolate - Delicious

Cocoa butter property

But cocoa butter is a special fat for many reasons. For one, it melts at body temperature, meaning that it can be stored as a solid but becomes a liquid when it comes into contact with the human body. This makes it ideal for lotions. Moreover, it contains natural antioxidants, which prevent rancidity, so it can be stored for years without going off.


From a psycho-physics perspective, meanwhile, brittleness and the sound associated with cracking open a chocolate are linked with freshness, which again adds to the enjoyment of eating chocolate with a “snap.”

Making Type V cocoa butter crystals

Type V is an extremely dense fat crystal. It gives the chocolate a hard, glossy surface with an almost mirror-like finish, and a pleasing “snap” when broken. It has a higher melting point than the other crystal types, melting at 34 ° C, and so only melts in your mouth. Because of these attributes, the aim of most chocolatiers is to make Type V cocoa butter crystals.

From raw coca beans to chocolate

I know this because I have eaten a raw cocoa bean and it tastes horrible: it is fibrous, woody, bitter, and bland; there is no fruitiness, no hint of a chocolate taste, and certainly no reason to taste one again. It takes quite a bit of engineering to turn these rather exotic-looking but dull-tasting beans into chocolate.

Choosing the beans

But what is much less talked about is that, just like coffee and tea, different varieties of bean and different techniques of preparation create vastly different tastes. A detailed understanding of both is required to buy the right beans, and when it comes to creating the finest chocolates this knowledge is closely guarded.

Maillard reaction

It is no exaggeration to say that without the Maillard reaction the world would be a much less delicious place: it is the Maillard reaction that is responsible for the flavor of bread crust, roasted vegetables, and many other roasted, savory flavors. In this case, the Maillard reaction is responsible for the nutty, meaty flavors of chocolate, while also reducing some of the astringency and bitterness.

History of cocoa

The Olmecs and then the Mayans, who first cultivated chocolate, drank it this way, and it was revered as a ceremonial drink and an aphrodisiac for hundreds of years. The cocoa nuts were even used as currency.

Adding Milk to Cocoa

For some, even with the addition of 30 percent sugar, this form of chocolate was still too bitter, and so another ingredient was added, one that profoundly affected its taste: milk. This reduces the chocolate’s astringency quite considerably, giving the cocoa an altogether milder—and the resulting chocolate an altogether sweeter—flavor. The Swiss were the first to do this in the nineteenth century, adding the plentiful milk powder produced by the fledgling Nestlé company,

Caffeine and theobromine

There are plenty of people, including myself, who are addicted to eating chocolate, and the reason may not just be its taste. It also contains psychoactive ingredients. The most familiar one is caffeine, which is present in small proportions in the cocoa bean, and so ends up in the chocolate via the cocoa powder. The other psychoactive ingredient is theobromine, which is a stimulant and antioxidant, like caffeine, but is also highly toxic to dogs. Many dogs die every year from eating chocolate, mainly around Easter and Christmas.

Gel - Marvelous

From liquid gel to air gel

Their cunning idea was to replace the liquid with a gas while it was still inside the jelly, and so use the pressure of the gas to keep the skeleton from collapsing.

Replacing liquid with gas

But when he raises the temperature of the whole jelly above the “critical temperature”—the point at which there is no difference between a gas and a liquid because both have the same density and structure—the whole liquid becomes a gas without going through the destructive process of evaporation.


This is a stroke of genius: under the pressure from the autoclave, the newly created gas cannot escape from the jelly and so the internal skeleton stays intact. “All that remains is to allow the gas to escape, and there is left behind a coherent aerogel of unchanged volume.”

Why is the sky blue?

When light from the sun enters the Earth’s atmosphere, it hits all sorts of molecules (mostly nitrogen and oxygen molecules) on its way to Earth and bounces off them like a pinball. This is called scattering, which means that on a clear day, if you look at any part of the sky, the light you see has been bouncing around the atmosphere before coming into your eye. If all light was scattered equally, the sky would look white. But it doesn’t. The reason is that the shorter wavelengths of light are more likely to be scattered than the longer ones, which means that blues get bounced around the sky more than reds and yellows. So instead of seeing a white sky when we look up, we see a blue one.

Aerogel foams

Aerogel foams have other interesting properties, the most remarkable of which is their thermal insulation—their ability to act as a barrier against heat. They are so good at this that you can put the flame of a Bunsen burner on one side of a piece of aerogel and a flower on the other and still have a flower to sniff a few minutes later.

Building with aerogel

Well, there is, of course, triple glazing and quadruple glazing, which work by introducing a new layer of glass and so a new barrier to the heat transfer. But glass is dense, so these windows get heavier and bulkier and less transparent the more layers there are. Enter aerogel. Because it is a foam, it has within it the equivalent of a billion billion layers of glass and air between one side of the material and the other. This is what makes it such a superb thermal insulator.

Space technology usage

Aerogels are particularly suitable for this application because not only are they the best insulators in the world, but they are also extremely light, and when you’re launching spacecraft out of the gravitational pull of the Earth, reducing weight matters rather a lot. Aerogel was used first in 1997 on the Mars Pathfinder mission and has been used as an insulator on spacecraft ever since.

Plastic - Imaginative

Billiards today

The game of pool evolved from billiards, a fifteenth-century Northern European game that started in royal palaces and was essentially an indoor version of croquet. This is why the table surface was colored green, to simulate grass.

Chemical engineering and material science

These days it is hard to believe that anyone could make fundamental chemical discoveries in their shed. But in the late nineteenth century, the beginning of the golden age of chemical engineering, a growing understanding of chemistry coincided with entrepreneurial opportunities for making money out of the invention of new materials. It was also easy and cheap to get hold of chemicals, sales of which were mostly unregulated.


Despite the existence of earlier plastic-like materials, celluloid is widely recognized as being the first commercial moldable plastic. At the International Exhibition of 1862, the British metallurgist, chemist, and inventor Alexander Parkes presented a very curious substance to the world, one made of vegetable matter but that was hard, transparent, and plastic. He called it Parkesine.

Celluloid boom

The celluloid business boomed in the 1870s and the material was molded into a huge variety of shapes, colors, and textures. Importantly, it could be made to closely resemble much more expensive materials such as ivory, ebony, tortoiseshell, and mother of pearl, and the early forms of plastic were used primarily in this way.

Plastics in photography

HYATT: You think plastic photographic plates will make it cheaper? EASTMAN: I want to turn photography into something everyone can do. So cheap and easy that you could take a camera to a birthday party, or a picnic, or on holiday, or — HYATT: To the beach! EASTMAN: Precisely! To do that, we need to make the camera smaller and lighter. But crucially I need to get rid of the heavy glass plates.

Birth of Kodak camera

The trick is to put the photographic emulsion on to a long flexible strip. That way twenty or thirty pictures can fit rolled up in a tiny canister. I am calling it a Kodak camera, and everyone will be able to afford one. I will bring photography to the whole world!

Motion pictures with plastic

The invention of the roll of film, made possible by the use of celluloid plastic, led directly to the technology of motion pictures. The idea that a picture could be made to “move” by sequentially showing small changes in the image had been known for hundreds of years, but without a flexible transparent material, the only way it could be made to work was using the rotating cylinder of a zoetrope.

Other uses of plastic

The plastics that followed celluloid, such as Bakelite, nylon, vinyl, and silicone, built on its creative power and have also had an important impact on our cultural psyche. Bakelite became a moldable replacement for wood at a time when the telephone, radio, and television were being invented and needed a new material to embody their modernity. Nylon’s sleekness took on the fashion industry, replaced silk as the material for women’s stockings, and then spawned a new family of fabrics, such as Lycra and PVC, as well as a group of materials called elastomers, without which all our clothes would be baggy and our pants would fall down.

Glass - Invisible

Raw material

There is a lot of quartz in the world because the two most abundant chemical elements in the Earth’s crust are oxygen and silicon, which react together to form silicon dioxide molecules (SiO2).

How glass is created

As the liquid gets cooler, the SiO2 molecules have less and less energy, reducing their ability to move around, which compounds the problem: it gets even harder for them to get to the right position in the crystal structure. The result is a solid material that has the molecular structure of a chaotic liquid: a glass.

Drinking with glassware

Until this time, drinking vessels had been opaque, made of metal, horn, or ceramic. The appreciation of wine was based solely on the way it tasted. The invention of drinking glasses meant that the color, transparency, and clarity of wine became important, too. We are used to seeing what we drink, but this was new to the Romans, and they loved it.

Colored glass

Colored or stained glass windows became a means of expressing wealth and sophistication, changing entirely the architecture of the European cathedral. Over time the artisans making stained glass for cathedrals became as high status as the masons who cut the stone, and in Europe the new art of glazing blossomed.

Telescopes and microscopes

What is certain, though, is that without a telescope you can’t see that Jupiter has moons, or that Pluto exists, or make the astronomical measurements that underpin our modern understanding of the universe. Similarly, without the microscope, it is impossible to see cells such as bacteria and to study systematically the microscopic world, which was essential to the development of medicine and engineering.

White light

Newton’s moment of genius was to notice that a glass prism not only turned “white” light into a mixture of colors, but could also reverse the process. From this, he deduced that all of the colors created by a piece of glass were already in the light in the first place. They had traveled all the way from the sun as a ray of mixed light, only to be split up into their constituent colors when they hit the glass.

Pyrex and chemistry labs

You only have to go to any chemistry lab to see that the transparency and inertness of the material make it perfect for mixing chemicals and monitoring what they do. Before the glass test tube was born, chemical reactions were performed in opaque beakers, so it was hard to see what was happening. With glass, and especially with a new glass called Pyrex that was immune to thermal shock, chemistry as a systematic discipline really got going.

Glass and scientific revolution

Whether the relationship between glass technology and the seventeenth-century scientific revolution really is a simple case of cause and effect is an open question. It seems more likely that glass was a necessary condition rather than the reason for it. However, there is no doubt that glass was largely ignored in the East for a thousand years. And during this time, glass revolutionized one of Europe’s most treasured customs.

Beer and glass

Drinking beer from a plastic cup is a completely different experience to drinking from a glass. Not only does plastic taste different, but it also has a lower thermal conductivity, a property that makes it feel warmer than glass, reducing the satisfaction of drinking an ice-cold beer.


This new generation of toughened glass has a layer of plastic in its middle, which acts as a glue keeping all the shards of glass together. This layer, known as a laminate, is also the secret behind bulletproof glass, which is essentially the same technology but with several layers of plastic embedded at intervals within the glass.

Glass with safety

This trend is likely to increase, the shops using glass not just to present their wares but to protect them too. This same laminated glass has been proposed as the material for new safety beer glasses, which would put an end to the use of glass as a weapon in bars and pubs. It is now impossible to imagine a modern city without glass.

Carbon - Unbreakable

Diamonds are not forever

But diamonds are not forever, at least on the surface of this planet. It is, in fact, diamond’s sibling structure, graphite, that is the more stable form, and so all diamonds, including the Great Star of Africa in the Tower of London, are actually turning slowly into graphite.


This is how a pencil works: as you press it on the paper you break the van der Waals bonds and layers of graphite slide across one another, depositing themselves on the page. If it weren’t for the weak van der Waals bonds, graphite would be stronger than diamond. This was one of the starting points for Andre Geim’s team.

How is diamond formed?

All materials prefer to change from less stable to more stable structures, and because the diamond structure is less stable than graphite’s, it requires very high temperatures and pressures to persuade it to change in the opposite direction. These conditions exist inside the Earth’s crust, but it still takes billions of years to grow a big diamond crystal.