Seeing Further (34 page)

That was to change. During the Industrial Revolution, the high price of steel meant that many large engineering projects were carried out that used instead cast iron, which is brittle and prone to failure. The Dee Bridge disaster of 1847 was one such: Robert Stephenson’s structure in Chester collapsed as a train passed over it, killing five people. This was why Henry Bessemer’s new process for making steel was greeted with jubilation: the details, announced at a meeting of the British Association in 1856, were published in full in
The Times.
Bessemer himself was lauded not just as an engineer but as a scientist, being elected a Fellow of the Royal Society in 1879.

Bessemer’s process controlled the amount of carbon mixed with iron to make steel. That the proportion of carbon governs the hardness was first noted in 1774 by the Swedish metallurgist Torbern Bergmann, who was by any standards a scientist, teaching chemistry, physics and mathematics at Uppsala. Bergmann made an extensive study of the propensity of different chemical elements to combine with one another – a property known as elective affinity, central to the eighteenth-century notion of chemical reactivity. He was a mentor and sponsor of Carl Wilhelm Scheele, the greatest Swedish chemist of the age and a co-discoverer of oxygen.

Oxygen, as a component of air, was the key to the Bessemer process. It offered a way of removing impurities from pig iron and adjusting its carbon content during conversion to steel. A blast of air through the molten metal turned impurities such as silicon into light silica slag, and removed carbon in the form of volatile carbon dioxide. Pig iron contains as much as 4 per cent carbon; steels have only around 0.3–2 per cent. Meanwhile, the heat produced in these reactions with oxygen kept the iron molten without the need for extra fuel (coke was expensive). Basically the same process was invented in Kentucky in the late 1840s by an American inventor, William Kelly, but he had no commercial success with it and went bankrupt in 1857, in the process losing his patent claims to Bessemer.

It was long known that steel can be improved with a spice of other elements. A dash of the metal manganese helps to remove oxygen and sulphur from the iron, and most of the manganese currently produced globally is used for this purpose. Manganese also makes steel stronger, while nickel and chromium improve its hardness. And chromium is the key additive in stainless steel – in a proportion of more than about 11 per cent,
it makes the metal rust-resistant. Most modern steels are therefore alloys blended to give the desired properties.

But is this science? Some of the early innovations in steel alloys were chance discoveries, often due to impurities incorporated by accident. In this respect, metallurgy has long retained the air of an artisan craft, akin to the trial-and-error explorations of dyers, glassmakers and potters. But the reason for this empiricism is not that the science of metallurgy is trivial; it is because it is so difficult. According to Rodney Cotterill, a remarkable British physicist whose expertise stretched from the sciences of materials to that of the brain, ‘metallurgy is one of our most ancient arts, but is often referred to as one of the youngest sciences’.

One of the principal difficulties in understanding the behaviour of materials such as steel is that this depends on its structure over a wide range of length scales, from the packing of individual atoms to the size and shape of grains micrometres or even millimetres in size. Science has trouble dealing with such a span of scales. One might regard this difficulty as akin to that in the social sciences, where social behaviour is governed by how individuals behave but also how we interact on the scale of families and neighbourhoods, within entire cities, and at a national level. (That’s why the social sciences are arguably among the hardest of sciences too.)

The mechanical properties of metals depend on how flaws in the crystal structure, called defects, move and interact. These defects are produced by almost inevitable imperfections in the regular stacking of atoms in the crystalline material. The most common type of stacking fault is called a dislocation. Metals bend, rather than shattering like porcelain, because dislocations can shift around and accommodate the deformation. But if dislocations accumulate and get entangled, restricting their ability to move, the metal becomes brittle. This is what happens after repeated deformation, causing the cracking known as metal fatigue. Dislocations can also get trapped at the boundaries between the fine, microscopic grains that divide a metal into mosaics of crystallites. The arrest of dislocations at grain edges
means that metals may be made harder by reducing the size of their grains, a useful trick for modifying their mechanical behaviour.

To understand all of this, one needs a variety of microscopic techniques for investigating metal structure at different levels of magnification. It has also now become possible to simulate the behaviour of vast numbers of atoms on a computer, allowing researchers to relate the properties of dislocations and grains containing thousands or millions of atoms to the packing of constituent particles at the atomic scale.

This sort of insight is making it possible to design metal alloys from the drawing board – figuring out what combinations of elements and arrangements of atoms will supply particular properties, and then attempting to make them. That’s true not just for mechanical properties such as strength and hardness but also for electrical and magnetic properties, paving the way for new batteries and super-strong magnets. No one can question that this is hard science, demanding the skills of physics and chemistry as well as the expertise and experience of materials scientists. Among the remarkable metals that have emerged from such research are alloys that can remember shapes, regaining them when bent and then gently warmed; metals that change shape when placed in magnetic fields; metals that don’t expand when they get warm (essential for finely engineered devices such as watches); and metals that turn heat into electricity, offering new possibilities in refrigeration. Yet as with so much applied science, the truly ‘scientific’ aspects of metal engineering tend to be overlooked by the time these substances reach the marketplace: they are just ‘stuff’, products of a kind of industrial alchemy that passes unquestioned because it is deemed simultaneously prosaic and utterly mysterious.

We have also divers mechanical arts … and stuffs made by them; as papers, linen, silks, tissues …

Bacon’s
New Atlantis
is a favourite hunting ground for those who like to find predictions of tomorrow’s technologies. With a little imaginative licence, you can find within it intimations of submarines, loudspeakers, even lasers. But even Bacon’s fertile mind fails to anticipate that entirely new
classes
of materials might be invented. He does, however, recognise the transformative value of the textile fabrics of everyday life, and it is not hard to imagine him grasping in an instant the idea that approximations to silk might be made from oil, or the genuine article obtained without the aid of spiders and silkworms.

Today, the very notion of ‘synthetic’ in materials is almost synonymous with plastics: that’s to say, with the Protean substances made of long, chainlike polymer molecules with backbones of carbon. Nature’s structural fabrics – silk, hair, muscle, horn, wood and so forth – are also essentially carbon-based polymer materials. But whereas they are composed almost entirely of just two classes of molecule – proteins and polysaccharides – synthetic plastics have a dazzling diversity of composition.

Plastics open the most revealing window on our relationship with human-made materials and their associated technologies. In many ways, they serve in this regard as a proxy for engineering technologies in general, tracing a complex path between excitement, opportunity, disenchantment, distrust, environmental concerns and even fetishism. Roland Barthes understood this: plastics, he said, are the ultimate representation of technologists’ abilities to transform matter: ‘the quick-change artistry of plastic is absolute: it can become buckets as well as jewels.’ Plastics offer ‘the euphoria of a prestigious free-wheeling through Nature’ – a poetic description of Bacon’s technological utopianism, if ever there was one.

The earliest plastics, invented in the nineteenth century, were semi-natural materials regarded as substitutes for wholly natural ones. Celluloid is made from the cellulose fibres of plants: Christian Schönbein, a Swiss-German chemist who also pioneered the fuel cell and discovered ozone, found in 1832 that cotton fibres could be dissolved in nitric acid to form a glutinous material, cellulose nitrate, that could be moulded and hardened.
John and Isaiah Hyatt, two American brothers, discovered three decades later that castor oil or camphor made this material more malleable and workable, and they marketed it in the 1860s as a kind of imitation ivory, used in billiard balls and false teeth. But it was highly inflammable, even explosive – one form of cellulose nitrate, called gun cotton, was used as an artillery propellant, while celluloid in photographic movie film led to many a reel (and sometimes a cinema) going up in smoke.

A role for polymers as cheap mimics of expensive natural materials was furthered by the serendipitous invention of Bakelite in 1905: this dark resin aped the texture of mahogany. And rayon, another polymer derived from cellulose and marketed from the 1880s, was regarded as a kind of artificial silk – an epithet also attached to nylon, which the American company DuPont sold first for toothbrush bristles and then more lucratively in women’s stockings from the late 1930s. Nylon has the better claim: the chemical constitution of its polymer chains is somewhat similar to that of the protein molecules that make up real silk.

So the initial promise of polymers was to provide ‘luxury for all’: materials resembling those only the wealthy had previously been able to afford. They were egalitarian materials: as Barthes put it, ‘they aimed at reproducing cheaply the rarest substances, diamonds, silk, feathers, furs, silver, all the luxurious brilliance of the world’. What’s more, the raw ingredients came from cheap oil or, in the case of Bakelite, from a waste product of turning coal into coke. Thus they offered wonders ‘for free’, and in this sense were a part of the utopian vision that science seemed to promise in the inter-war years. Henry Ford even experimented with an all-plastic car made from extracts of soya beans.

But this vision palled after the Second World War, partly because of shoddy manufacturing. PVC (polyvinylchloride) raincoats had an unpleasant texture and gave off smelly vapours when wet. Polystyrene products were brittle in ways that wood and metal never were. Plastics no longer seemed like cheap luxury, but merely cheap. ‘Plastic has climbed down, it
is a household material’, Barthes announced in the mid-1950s. ‘It is the first magical substance which consents to be prosaic.’

And so the plastics industry made that instead its selling point. No longer imitating luxury goods, plastic openly advertised its synthetic nature in garish colours that always looked factory-fresh. These materials were cheap, disposable and convenient: for housewives, much was made of plastics’ wipe-clean character, transferable to just about any surface thanks to rolls of adhesive sheeting. The virtue of domestic convenience was exemplified by Teflon, the substance discovered (again serendipitously) at DuPont in the 1930s and later used in ‘non-stick’ kitchenware.

Historian Jeffrey Meikle of the University of Texas at Austin suggests that plastics thus introduced a ‘democratisation of things’ in the post-war economic expansion that made a dizzying variety and quantity of goods available to everyone. But this ultimately spawned a backlash against the ‘miracle materials’, which became emblematic of all that was superficial and wasteful in modern society. And hazardous too: it began with children being suffocated by plastic bags, but during the 1960s and 1970s the dangers started to look far more insidious. The molecular building blocks of PVC were linked to liver cancers among workers in the manufacturing plants, while some of the ingredients used as so-called plasticisers to soften plastics have been implicated as carcinogens and hormone mimics, which disrupt the human endocrine system.

Meanwhile, it became increasingly hard to see a link between these mass products and genuine science. In the World Fairs of the inter-war years, plastics were brought to the public by men in white coats, gazing into test tubes. But could a polymer scientist really belong to the same lofty caste as a geneticist or a particle physicist?

Yet once again, from a scientific and engineering point of view there is an awful lot of complexity to polymer science. These chainlike molecules can get entangled and flow in unusual ways while they are fluid. Engineering specific properties in polymers is a matter of controlling the
microstructure, just as it is for metals: modifying the way the chains line up in a more or less orderly manner, say, or controlling their branching. As chemists gradually deduced how to regulate such things, they became capable of synthesising remarkable engineered polymers such as Kevlar, which is strong and tough enough to deflect bullets and tether oil rigs.

In nature this sort of structural tuning is exquisitely managed in protein-based polymers such as silk, a complex collage of tiny crystal-like regions in a disorderly, flexible matrix that creates a material stronger, weight for weight, than steel. Scientists have been attempting to make artificial silk for decades – one of the latest tricks is to produce the silk protein in the milk of genetically engineered goats, a Baconian vision for sure. But a persistent obstacle here is that the superior properties of silk thread arise not just from its chemical composition but from the way the polymer molecules are marshalled, aligned and organised as the threads get spun.

From the utopianism of the 1930s to the bland consumerism of the 1960s and the sleek monochrome minimalism of the 1980s, the mood of the developed world can be gauged from its polymer consumables. Today our bulk plastics are struggling towards a more environmentally friendly image, being biodegradable, made from non-oil-based ingredients, or more easily recycled. Meanwhile, high-tech plastics infiltrate the information technology once monopolised by silicon. Electronic circuits are being written with plastic, manufactured with cheap printing technology instead of demanding expensive high-vacuum conditions. Glowing television screens can be created from all-plastic light-emitting diodes on sheets as thin and flexible as paper.