Porcelain

A pricey kitchen stove left Charles C Mann with a question: what on earth is Dekton?

This is our fifth article from Issue 26, which arrived with print subscribers last week. In it, Charles C Mann explains how he learned to love porcelain.

---

I am aware that I am a bit of a kitchen equipment nerd, okay? So maybe you don’t have to roll your eyes theatrically like my cousins did when I tell you my wife and I got a swanky induction cooktop that was, well, kind of pricey for a middle-class couple? And maybe you can imagine my irritation when it turned out that the swanky induction cooktop – did I mention it was pricey? – did not include the necessary smooth cooking surface above the induction burners, and that you had to buy the cooking surface separately from a separate company, a fact not exactly advertised on the website, and that the surface could not be tempered glass, which is what I had thought was on top of induction ranges, a sheet of which costs maybe $30 per square foot, but a special, newly created material called Dekton that cost five times as much. ‘What on earth is Dekton?’ I asked the heavens, or at least my wife.

My question turned out to have two answers. The first is that Dekton is an artificial material invented by the Spanish company Cosentino in 2013 that is amazingly heat-, pressure-, scratch-, shatter-, and stain-resistant – a high-tech substance that would have been almost impossible to fashion even thirty years ago. The other answer, equally true, is that Dekton is basically porcelain.

Paradoxically, porcelain is both one of humankind’s oldest high technologies and one of its newest. The earliest proto-porcelain was created more than three thousand years ago, and was, for the time, an astonishing technical feat, as unprecedented as the roughly concurrent development of iron metallurgy. Iron technology had its second flowering in the mid-nineteenth century, when the invention of the Bessemer and Siemens-Martin refining processes allowed manufacturers to produce cheap, high-quality steel. Porcelain is having its resurgence today – indeed, high-tech ceramics are key elements in the ongoing upsurge in materials science, the study of the relationship between a substance’s structure and its physical properties.

Much attention is rightfully focused now on the rise of the digital world and the explosive arrival of artificial intelligence. But that attention sometimes obscures the ongoing, equally important transformation of our physical world, the built environment, by materials science. Unleashing a cataract of innovation so ubiquitous as to be almost invisible, materials science has literally changed the walls around us. Porcelain is a reminder that the drive to create new types of matter has long played a powerful role in human history.

Kaolin

The initial steps toward porcelain occurred when potters in northern China started to tinker with an unusual clay, chalk colored and fine grained, called kaolin. Kaolin was known for its color, useful in paints, coatings, and fillers. Potters learned that subjecting this soft, white, unremarkable-looking mud to extreme temperatures produced startling effects.

Ordinary clay looks like amorphous glop but actually is composed of huge numbers of microscopic crystals. The crystals have an unusual structure: flat plates stacked atop each other like playing cards in a deck, loosely held together by hydroxyl groups (hydrogen and oxygen bound together, or -OH, in chemists’ terms). When clay is cooked in a kiln, the hydroxyl groups vibrate and break free, causing the plates to fall apart and reform into long, needle-shaped crystals that lock together into a sturdy structure. Meanwhile, the free hydroxyls merge, becoming water molecules that steam away in the hot kiln, leaving behind oxygen in the new crystals.

Kaolin clay is abundant in kaolinite, a mineral made of aluminum, silicon, oxygen, and hydrogen – Al₂Si₂O₅(OH)₄, with the parentheses meaning that each molecule has four hydroxyl groups. When heated in a kiln, kaolinite also loses its hydroxyls and reorganizes itself into a three-dimensional web of needle-like crystals. But when the temperature rises to about 1,200 degrees centigrade, well above the typical level for earthenware pottery, kaolin does something else. The silicon and oxygen break free, forming silica, which forms a thick liquid glass, filling all the spaces around and inside the web of needles, creating a dense, continuous, translucent matrix – porcelain.

In China, like everywhere else, ceramics had been a foundational industry for millennia. Clay was a primary part of construction (bricks, adobe, wattle-and-daub), cooking (pots, tableware), art (paints as well as sculpture), and even communication – clay tablets were the first surfaces used for writing. But porcelain was a giant leap, a concatenation of multiple innovations.

Ordinary kilns couldn’t reach the temperatures required to fire porcelain, partly because their exhaust vents, located on the ‘roof’, let out the hot air almost as fast as it was created, cooling the kiln. (This is a problem for conventional home fireplaces, which are fun to look at in use but wildly inefficient as a means of heating.) Chinese potters designed downdrafts, which forced the hot air to escape through floor vents, trapping the heat around the pottery. Alarmingly, ordinary kilns would shatter or even melt at such high temperatures. Chinese potters invented new types of heat-resistant brick. And so on.

Alltinktur

When Europeans first saw East Asian porcelain, probably in the thirteenth century, they were astounded. Harder, stronger, finer, smoother, and more lustrous than any other pottery, it became an obsessive object of desire, ‘white gold’ for the Continent’s wealthy and powerful. Enormous sets of gleaming white china became symbols of luxury – the private jets and invite-only clubs of the Renaissance era.

Unhappy about the high prices charged by the merchants who imported porcelain from Asia, European elites spent lavishly on efforts to make their own porcelain – and failed comprehensively for several centuries.

A key problem was that nobody on the Continent knew that porcelain was made from kaolin. Or that kaolinite alone didn’t actually contain enough glassy liquid silicate to make proper porcelain, so that Chinese potters added pulverized ‘China stone’ – a type of partly decomposed granite containing silicon – into the kaolinite.

Trying to make their wares porcelain-white, European potters added materials like tin oxide and ground glass to the clay, an approach that led to Italian maiolica, French faience, and Delftware. The results were often beautiful, but lacked porcelain’s impermeability to water, high tensile strength, and the distinctive ring made by porcelain cups when tapped with a spoon.

Enter Count Ehrenfried Walther von Tschirnhaus (1651–1708), a mathematician, physicist, and philosopher born in the Electorate of Saxony. Tschirnhaus initially studied math and philosophy but in his twenties became fascinated by porcelain. Beginning in about 1679, he conducted a series of experiments that used concave copper mirrors to beam intensely hot sunlight on multiple types of metals, minerals, and ceramics. Eventually he realized that glass lenses could outperform mirrors and invented a method of casting glass to make big, thick lenses for focusing sunlight, sending samples of the results to European monarchs in an unsuccessful quest to obtain financial backing to establish a science academy in Saxony.

In the winter of 1693–94, Tschirnhaus discovered a surprise: a type of clay that wouldn’t melt. Dug from Colditz, about 25 miles southeast of Leipzig, in Saxony, it contained kaolin (Tschirnhaus, of course, didn’t know this). Adding alabaster or chalk to the clay and heating the mix produced a hard, yellow, somewhat translucent ceramic that Tschirnhaus called ‘wax porcelain’. Unfortunately, he couldn’t produce it in quantity – his lenses could focus sunlight on an area of 10 to 15 square centimeters but not heat spaces of any size. When he tried making his porcelain in commercial kilns, their walls shattered or melted. Tschirnhaus was struggling to develop a better kiln when he was approached by Augustus the Strong, the ruler of Saxony.

A few years earlier, a young mountebank in Prussia named Johann Friedrich Böttger had let it be known that he had discovered the Alltinktur, an alchemical substance that cured any disease and turned base metal into gold. In a fine example of FAFO, Prussia’s gold-hungry king, who wanted to monopolize the Alltinktur, immediately ordered Böttger to be taken into ‘protective custody’. Böttger escaped into Saxony, whereupon he was seized by Saxony’s equally gold-hungry ruler Augustus the Strong, confined to an attic in a fortress outside Dresden, and ordered to produce gold. Böttger toiled for years, promising all the while to produce ‘alchymist gold’. Surprisingly, he was unable to deliver. Augustus grew exasperated and in 1704 asked Tschirnhaus to supervise work on the Alltinktur. Tschirnhaus, who evinced no interest in alchemy, invited Böttger to work with him instead on porcelain. To save his neck, Böttger grudgingly agreed.

Tschirnhaus, Böttger, and Gottfried Pabst von Ohain, a high-ranking mining official (in those days, the closest thing available to an earth scientist), developed a red clay that could be made into bricks suitable for porcelain kilns. In June 1708, Pabst von Ohain found a source of white clay – nearly pure kaolin, though he didn’t know it – and shipped it to the other two. Mixing the white clay with ground limestone and heating it in kilns made from the new red clay in August and September, Tschirnhaus single-handedly created a cup that looked and behaved very much like white Chinese porcelain.

He did not live to enjoy his triumph. In October, Tschirnhaus suddenly dropped dead, supposedly of dysentery. On his deathbed, he gave Pabst von Ohain a black box filled with documents. The box was found in Böttger’s belongings after his death, which may explain why he wrote to Augustus in March 1709, claiming to be the sole discoverer of the process to make porcelain. Augustus officially chartered the Royal Porcelain Manufacture in Meissen, another small town near Dresden, the following year and put Böttger in charge. It took ten more years for its workers to figure out that ‘China clay’ (or, more precisely, a similar local stone) was a better additive than limestone. Meissen then became Europe’s porcelain center. Augustus made so much money that he built a ‘Japanese palace’, filled it with Meissen copies of Asian originals, and crowed to visitors that he had beaten the Chinese – correctly, because Meissen porcelain was harder and less porous than the original.

Dekton

If Meissen was Porcelain 2.0, the Dekton for my cooktop is Porcelain 3.0 or more. Made by baking a slurry of ground porcelain, glass, and quartz into slabs, running the slabs through a huge hydraulic press that applies 25,000 metric tons of pressure, and hardening them at 1,200 degrees centigrade, Dekton took six years and almost $200 million to invent. Traditional ceramics contain microscopic voids and flaws that act as ‘stress concentrators’, focusing rather than diffusing the energy from impacts, which is what causes them to crack. The high pressure and heat used to produce Dekton cause atoms in the particles of kaolinite and quartz to diffuse across the boundaries where they touch, turning the entire thing into what amounts to a single solid mass. In consequence, Dekton has nearly eliminated porcelain’s long-standing weakness: its brittleness and structural fragility.

Dekton is but one part of an ongoing resurgence in porcelain, which itself is part of the still larger revolution in materials science. The field was founded in the 1940s and 1950s, when physicists, chemists, and engineers had to work together in the Second World War, the Cold War, and the space race. But it really took off in the 1980s and 1990s, with the development of precision measuring and manufacturing techniques. Most of its innovations have been incremental, but the accumulated total has had enormous impact in our daily lives.

To give a personal example, my late mother-in-law was injured permanently by slipping on a wet porcelain bathroom tile – something that happens to tens of thousands of people in the United States every year. In the past, firms made nonslip tiles by coating them with rough, jagged grains – a bit like laying sandpaper over the surface, and deservedly unpopular in the home. Ten years ago, Italian and Spanish tile manufacturers like Ceramica Sant’Agostino and Inalco introduced ‘wet-activated’ or ‘in-out’ tiles, with special crystalline compounds baked onto the surface. Dry, they look and feel like ordinary porcelain tiles. But when they are wet and someone steps on them, the pressure drives the water into thousands of pores on the surface, creating a suction-cup effect between foot and tile, instantly making them less slippery. (How much suffering will wet-activated tiles prevent? Back-of-the-envelope calculations suggest it would be equivalent, in terms of deaths prevented, to curing childhood cancers.)

Another personal example: My daughter, hit with a rare bone infection at age eleven, now has a porcelain hip joint – porcelain because the previous cobalt and chromium replacement joints can release metal ions into the bloodstream, which can migrate into the placenta of pregnant women, potentially harming the fetus. About the same time that ceramics firms introduced wet-activated tiles, researchers deployed 3D printing to create porous, lattice-like ‘bioceramic’ structures to replace defective bone. The structures are not permanent replacements but scaffolds that allow blood vessels and bone cells to migrate into the spaces in the bioceramic. Over time, the porcelain structure dissolves and is replaced by the patient’s own tissue. (The scaffold is expelled from the body.)

I could go on to talk about the use of nanotechnology to fill porcelain pores to enhance color depth and stain resistance, imprinting porcelain with silver ion layers to enhance antimicrobial activity, or the use of lithium disilicate to make ultrathin dental implants of unprecedented strength. But maybe the best way to say it is that my grandmother, who proudly displayed her mother’s eggshell-thin Meissen china on the sideboard, would have been astonished to find that I was cooking on a thin slab of porcelain, heedlessly dropping heavy pots of boiling water on its surface. But when I tried to explain how remarkable this is to my son, he gave me a blank look. He had never lived in a world that wasn’t made of porcelain.

---

Charles C Mann is a correspondent for The Atlantic.