by John Browne
Titanium metal will always be in the background, but it will never outmatch iron for its unique cheapness, ubiquity and versatility. Holding back titanium’s widespread use is the dated process by which titanium metal is extracted from its ore. The Kroll process, named after metallurgist William Kroll, that originally unleashed titanium’s potential as a metal in the 1940s, is still the most widely used method of production today. The Kroll process is extremely energy-intensive and so very expensive.12 As a result, titanium is an order of magnitude more expensive than steel and so, except for the most specialist applications, cheap steel is preferred over titanium. When weight is the chief concern, aluminium is usually chosen.
Titanium metal did not find the widespread application in society envisaged in the 1950s and production today is only about one ten-thousandth that of steel. This is all the more surprising considering that titanium is the fourth most abundant structural metal, after aluminium, iron and magnesium.
But titanium in its pure metallic form is only one half of its story. When titanium combines with oxygen atoms, with which it naturally bonds, it becomes titanium dioxide and that is so common in modern society that we rarely realise it is there.
Bright white titanium
As a Londoner every summer I go to Wimbledon where, before a match begins, I survey the immaculately mown lawns and meticulously drawn white lines of the tennis courts. The players come out of the grandstand, dressed head to toe in white, a tradition that stretches back to the first Lawn Tennis Championship in 1877. Whiteness was a symbol of wealth in the nineteenth century; today, thanks to titanium dioxide, both the courts’ lines and the players’ attire are a brighter shade of white.
We seldom pause to consider that white is everywhere in the world in which we live. In white-walled offices we wear white shirts and work on brilliant-white paper. We eat white foods and we use whitening toothpaste, because we think of whiteness as clean and pure. Adding white colouring to skimmed milk has been shown to make it more palatable.13 In almost every application, whiteness in the products we buy comes from the harmless additive E171, a code name for titanium dioxide. Using titanium dioxide, murky greys and pale yellows are turned to pure white, making life agreeable for the modern consumer.
I first learnt of the use of titanium as a whitening agent when I was Chief Financial Officer of the Standard Oil Company (Ohio) in the late 1980s. Quebec Iron and Titanium (QIT) was a subsidiary, formed in 1948 shortly after the discovery of the world’s largest deposit of ilmenite, a titanium iron oxide mineral, in the beautiful Lake Allard region of Quebec.14 After the iron had been separated out to make steel, we sold the titanium oxide slag to be used as white pigment.
On my yearly visits to QIT, from the air I could see the full scale of the ilmenite deposit, stretching out over an area the size of a hundred American Football fields, against the spectacular backdrop of Lakes Allard and Tio. The growth of the company over the last three decades had been relentless. In the 1950s titanium slag production grew from 2,000 to 230,000 tonnes and iron production from 2,700 to 170,000 tonnes. During the 1960s and 1970s a series of modernisation and expansion programmes was implemented as demand for titanium and steel products increased. Today QIT produces 1.5 million tonnes of titanium dioxide each year. But this causes barely a dent in the estimated global reserves of almost 700 million tonnes. Production can easily be stepped up to meet rising demand and so, unlike iron and oil, there has been little conflict over titanium reserves.
Like steel skyscrapers and silicon chips, manufactured whiteness is all around us, once a symbol of wealth but now a ubiquitous symbol of modern life. But why, of all the colours we could choose, are humans attracted to white? For the answer, we must go back to our understanding of light itself.
Why white?
In August 1665, Sir Isaac Newton drew the curtains of his study at Woolsthorpe Hall, Lincolnshire, save for a slit through which a sunbeam shone into the room. In the path of the beam he placed a glass prism that, as the light passed through, painted a spectrum on the opposite wall. With characteristic rigour he measured the dispersion of light across the room and from his results produced a revolutionary new theory of colour.15
For 2,000 years, since Aristotle wrote De Coloribus, it was believed that all colours were made from varying combinations of black and white, the polar opposites in our perception of colour. According to this theory, the colours of the rainbow were actually added to white light by a prism itself. To disprove this, Newton used an identical prism to show that the spectrum could be recombined into its original pure white state. Newton had demonstrated that colour was an intrinsic property of white light; he had ‘unwoven the rainbow’.16
Newton divided the spectrum into seven colours: red, orange, yellow, green, blue, indigo, violet – the choice of seven to accord with the seven notes of the diatonic music scale and the seven heavenly spheres. ‘But the most surprising and wonderful composition,’ Newton wrote, ‘was that of Whiteness … ’Tis ever compounded.’17 White light is the master of the rainbow; it is the basis from which all other colours emerge.
Sunlight, as opposed to the circular golden sun itself, is white light and so contains the full rainbow spectrum of colours. The sun emits these different colours of light in different proportions which, when combined, give the perception of white light.18 This is no coincidence: our eyes have evolved over billions of years so that they are adapted to make sunlight the whitest and brightest source of light. We see objects as white when they reflect different colours of light by the same proportions as are emitted from the sun. The colour white is essentially an imitation of sunlight; we paint objects white so that they are bright and outstanding.
In contrast, gold is a reflection of the circular sun in the sky, whose white image is turned golden by the dispersion of light rays in our atmosphere.19 We worship the sun, and so place a high value on gold. But the white light of the sun is so pervasive, like the white walls which surround us, that it goes almost unnoticed.
Since humans first moved into caves, we have sought to create a safe and hospitable environment in which our families and societies can live and develop. We have built barriers between us and the earth, rain and wind, separating ourselves from nature. In keeping walls white, we assert our control over the Earth’s destructive forces, which constantly batter, wear down and soil human constructions. The white interiors of our houses and office blocks create a brilliant glow, competing with that of the sun.
Beyond white
At first sight, the prevalence of whiteness from titanium dioxide, while surprising and important, lacks the flair of supersonic aircraft and deep-diving submarines. But on closer inspection, we find that titanium’s glow is as technologically sophisticated as the titanium frame of the Blackbird.
Titanium dioxide is not only incomparably bright; it is also clinically clean. Tiny nanoparticles of titanium dioxide absorb UV light from the sun. Coated in these particles, a wall disperses UV energy, which kills the bacteria that sit on the surface. A very thin layer on a window pane is transparent, but still absorbs UV light, which breaks up dirt on its surface. The coating also makes the glass surface repel water, so that when rain hits the surface droplets do not form and a thin sheet of water carries broken-down dirt away with it.20 Most recently, the same principle has been applied to produce self-cleaning clothes.21 By capturing light as well as reflecting it, titanium dioxide creates the immaculate environment in which we choose to live.
Titanium dioxide’s extraordinary properties also show up in its interactions with electrons. Like silicon, titanium dioxide is a semiconductor and so can be used to carry an electric current in photovoltaic cells (which are used for solar power generation). While silicon both absorbs light and contains electrons to carry electric current, titanium is only sensitive to ultraviolet light. This makes titanium dioxide very useful in sunscreen since UV light causes sunburn, but less useful in photovoltaic cells. To capture as much light as possible from the sun, a l
ight-sensitive dye is applied on top of the titanium dioxide nanoparticles.22
Technological innovations often come from the most unexpected places, and for titanium photovoltaic cells we have to look back to the development of silver halide photography at the end of the nineteenth century. Both silver halides and titanium dioxide are, by themselves, insensitive to most of the visible spectrum of light. Early photographic emulsions were only sensitive to bluer tones of light, and light at the red end of the spectrum was not picked up at all. In 1873, the German photographer Hermann Wilhelm Vogel discovered that certain dyes would improve the sensitivity of the photographic plates to different parts of the light spectrum. The dyes absorb photons from the sun causing electrons to be ejected. The energetic electrons then interact with nearby silver halide molecules. Vogel’s experiments led to much more accurate black and white photographs and, eventually, colour photographs. Similar dyes are used in titanium dioxide photovoltaic cells today, but rather than the ejected electrons turning silver halide grains to silver, the electrons are transported by the titanium dioxide semiconductor to electrodes, generating an electric current.
These photovoltaic cells are the latest twist in titanium’s fascinating relationship with sunlight. Along with white paints and artificial colourings, which mimic the light emitted from the sun, and sunscreen, which protects us from the sun’s harmful rays, titanium dioxide can now harness the sun’s energy to create electricity.
Titanium is one of three post-war ‘wonder elements’, along with uranium and silicon. Each serves to show how the world can be transformed by a new application of the Earth’s elements. Uranium did so most dramatically when its extraordinary energy was unleashed on the people of Hiroshima, but titanium, too, has shaped the post-war era in both its military and civilian applications. The influence of the elements stretches back thousands of years to the earliest human communities. It is therefore remarkable to think of the impact that these three elements have had within my lifetime.
After the Second World War, we were tempted to think that, because new uses had been found for them, these were ‘wonder elements’ which would continue to change the world; we were wrong. After the bombing of Hiroshima, great excitement was generated around uranium and its future applications in everything from a cure for cancer to climate control. Today, uranium is viewed with dread and uncertainty; the bright nuclear future that was dreamt up in the late 1940s has never been realised. Titanium, once seen as a high-performance structural metal, came to be employed in roles as mundane as Russian cutlery sets, and is now dominantly used as a ubiquitous whitener, something that was not envisaged sixty years ago.23 And silicon, which first appeared in the public eye in 1948 when the invention of the transistor was announced, was ignored by most people in the ensuing years. Silicon, though, has had the greatest impact of all the post-war ‘wonder elements’, enabling the development of smaller, faster and cheaper computers that have placed immense processing and communication powers into our hands, an extraordinary transformation for a material that for many millennia was ignored as useless, worthless sand.
SILICON
ON A SMALL STRETCH of beach to the south of Acre in modern-day Israel, the Na’aman River, heavy with silt, meets the Mediterranean. When the tide retreats, clean white sands, rich in silica, are revealed. Here, recounts Vannoccio Biringuccio, the medieval metallurgist, a group of merchants ‘driven there by the fortunes of the sea’ stopped in order to eat.1 Finding no stones on the beach, the crew took lumps of nitre, a type of soda, from the ship’s hold to support their cauldrons. In cooking the food they saw the rocks of that place converted into a flowing, lustrous material … Thus gave beginning to glass making.’2
By chance, these merchants had transformed simple grains of silica, consisting only of atoms of silicon and oxygen, into an object of beauty. From this initial discovery, came a profusion of glass innovations: glass beads in ancient Egypt; glass vases in the Near East; and glass mirrors in Venice.3 ‘Through many experiments and by addition or subtraction at will,’ writes Biringuccio, the ancients and moderns have ‘done so much that one can perhaps believe it would be difficult to go any farther with this art. For, as is evident, an infinite number of beautiful things are made from it.’4
Throughout its 5,000-year history, the versatility of glass has enabled the creation of startlingly original objects of beauty. The ability to keep transforming glass in this way is not a result of the tools used by the artisan, which have remained largely the same. Glassblowing, invented in the first century in the Near East and perhaps the most important innovation in the history of glassmaking, is still the technique by which most decorative glass is produced today. Rather, continued innovation in producing decorative glass is a result of the intrinsic malleability of the atomic arrangement of glass. When grains of sand are melted with soda, the resulting liquid is so viscous that, as it cools into a solid, atoms cannot move into position quickly enough to form a regular crystal structure.5 Silicon and oxygen become frozen into a disordered structure that resembles a liquid, and so can be shaped into almost any form.6 The random atomic structure of glass also leaves room for atoms of other elements to be accommodated. By adding small amounts of impurities, glass can be made with different optical properties: transparent, translucent, opaque and opalescent. And all of this can be done in a limitless variety of colours.
The transformation of sand into glass was merely one of silicon’s greatest contributions to human progress. The second, invented many millennia later, comes from pure silicon crystals. The unusual electrical properties of these crystals enable their use in photovoltaic cells, which generate electricity from sunlight, and in transistors, which form the processing core of computers. The transistor is arguably the most world-changing of all of silicon’s uses, placing extraordinary computational and communication power in the hands of everyone.
Harnessing the optical and electrical properties of this extraordinary element, humanity has created objects of great beauty and powerful technology that continue to amaze, delight and inspire us. But the story of silicon for most of its 5,000-year history is the story of glass. And the most important place in the history of glass is Venice where, during the Renaissance, decorative glasswork reached its zenith as an art form.
GLASS
On a sunny April morning in Venice, I walked past the window of an antique shop off the Campo Santo Stefano and spotted the tail end of an elaborate art-deco elephant. The shop is in a very narrow alley and so, among the crowds of tourists, I could not step back to take in the full display. Returning to get closer to the window, I passed a series of wooden cubicles, presenting glass vases and goblets, before the black and turquoise elephant appeared.7 The delicate twist of its trunk makes crystal clear the artistry of the glass workers on the nearby island Murano, where most Venetian glass is made. Elephants, with many protuberances which must be crafted and individually joined to the hulking body, are some of the most difficult glass objects to create. I have been collecting them for about five years. I first became fascinated by glass animals when, in Venice, I met a former director of the Musée du Louvre, whose extensive collection I greatly admired. Years later, I discovered that my partner collected sculptures of elephants, among the noblest creatures on Earth; they are highly intelligent and form deep social bonds. Combining my partner’s interest in elephants with my love of Venetian glass, our collection had already begun.
Even before entering the shop I knew I was going to buy the elephant. From my body language that must also have been clear to the shop owner; I probably ended up paying too much. I now own more than a hundred glass elephants, and the herd is growing. This particular one was created in 1930 by Napoleone Martinuzzi, working in the studios of the manufacturer Venini. Under Martinuzzi’s artistic direction, Venini became an innovator of new types and forms of glass. By introducing clean and elegant shapes and an intense new colour palette, he contributed to a revival of the Murano glass industry.8
; Murano’s glass industry first took off after 1291, when the Great Council ordered the glass furnaces in Venice to be moved to the island as they were causing many fires in the city.9 The same soda and silica used by Egyptian and Islamic glassmakers was imported into Murano along trade routes with the East. These commercial links also provided a readily available export market, giving local glassmakers an edge over their competitors. In the island’s glass workshops, artisans created objects of outstanding beauty using the same blowpipes, crimps and shears that are still employed on the island today.
At Murano, ‘the best glasswork is made,’ wrote Biringuccio. ‘It is of greater beauty, more varied colouring, and more admirable skill than that of any other place.’10 Georgius Agricola, a contemporary of Biringuccio, also valued the artistry of the Muranese artisans. During the Feast of the Ascension, he admired the diverse range of glass objects for sale: ‘goblets, cups, ewers, flasks, dishes and plates, panes of glass, animals, trees, and ships’.11 In Renaissance Venice, glass became an extraordinary art form. Made from common sand, glass was not rare, but the rare skill needed to create beautiful glass objects meant that they were valued as highly as many precious minerals.
Among the most important inventions to come out of fifteenth-century Venice was cristallo, a type of glass ‘as colourless and transparent as quartz’.12 Impurities gave most glass an unpleasant yellow, grey or green hue, but using high-quality silica, made from crushed quartz river pebbles, purified soda and innovative furnace techniques, Venetian glassworkers created a crystal-clear and highly sought-after product.13