Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World

by Mark Miodownik

minerals result in different kinds of clay. In the case of terra cotta, the crystals are usually a mixture of quartz, alumina, and rust, whi...

When this is heated up, the first thing that happens is that the water evaporates, leaving the tiny crystals aggregated in a kind of sand castle with lots of holes where the water used to be. But at high temperatures something special happens: atoms from one crystal will jump on to another nearby crystal and then back again. The atoms in some crystals, however, do not return to their original position, and gradually bridges of atoms are built between the crystals. Eventually,...

The reason the atoms do this is the same reason why any two chemicals react: within each crystal, all of the atom’s electrons are part of a stable chemical bond with its neighbors—they are, as it were, “occupied”—but at the edges and surfaces of the crystal, there are “unoccupied” electrons, ones that have no other atoms to bind to, the equivalent of loose ends. For this reason, all of the atoms in a crystal seek a position within the body of the crystal rather than at its surface; or, put another way, those atoms...

Usually, when the crystals are cold, these atoms don’t have enough energy to move around and do something about

their predicament. But when the temperature is high enough, the atoms can move around: they set about reorganizing themselves so that as few of them as possible are forced to inhabit a position at the surface of the crystal—so that, in fact, there is less surface overall. In doing so, they reshape the crystals to fit together as fully and economically as possible, eliminating the holes between them. Slowly but surely the collection of tiny crystals become a single material. It’s not magic, but it is magical.

It was the potters of the East who solved the problem of fragility and porosity. Their first step was to realize that if earthenware was covered with a particular kind of ash, this ash would transform during firing into a glass coating that would stick to the outside of the pot. This glass skin would seal all the pores on the outside of the earthenware. And by varying the composition and distribution of the glaze, the pots could be colored and decorated. This not only stopped water getting in but it suddenly opened up a whole new aesthetic realm for ceramics.

While glazing prevents water from getting into fired clay, it doesn’t solve the problem of porosity within the body of the ceramic, which is how the cracks start in the first place. So tiles are still relatively weak, as are glazed terra cotta cups and bowls. This problem was also solved by the Chinese, but it involved the creation of a completely new type of ceramic altogether. Two thousand years ago, while looking for a way to improve their ceramics, the potters of the Eastern Han Dynasty started experimenting not just with different kinds of clays but with clays of their own concoction, mixing into them minerals that might never end up in a river. One such additive was the white mineral kaolin. Why? No one knows. Perhaps it was purely in the spirit of inquiry, perhaps because they liked the color.

No doubt they tried all sorts of different mixtures, but eventually they hit upon a particular combination of kaolin and a few other ingredients, such as the minerals quartz and feldspar, which created a white clay and, when fired, a nice-looking white

ceramic. This was no stronger than earthenware, but, unlike any other clay they knew, if they increased the temperature of the furnace to a very hot 1300°C, it did something strange. The clay turned into an almost watery-looking solid: a white ceramic that had a near perfectly smooth surface. It was quite simply the most beautiful ceramic that anyone had ever seen. It was also stronger and tougher than any ceramic had any right to be. It was so strong that cups and bowls could be made that were extremely thin, almost as thi...

From that moment on in Chinese history, different royal dynasties were associated with different types of imperial porcelain. The dynasties showed off their ceramics by creating incredibly beautiful vases and ceremonial bowls with which they decorated their palaces. But they realized that for their honored guests to really marvel at the translucency and lightness of this new material they needed to feel it as well as see it. Tea drinking provided a perfect way to do so. Serving tea to one’s guests in porcelain cups became an expression not just of technical sophistication but of cultural refinement as it grew eventually into a ceremonial ritual.

Chinese porcelain was so superior to any other ceramic that when traders from the Middle East and the West came into contact with it, they immediately realized how valuable it would be as a commodity. They exported not just the porcelain but the tea-drinking ritual as well, which together became the ambassadors of Chinese culture, causing a sensation wherever they went. At this time Europeans were

still drinking from wood, pewter, silver, or earthenware. Porcelain was physical evidence of just how much more technically advanced the Chinese were than anyone else in the world. To have a set of porcelain tea cups and to serve the best China tea immediately set you apart. Consequently an enormous trade in this sublime white porcelain, called “white gold” or “china,” started up. The trade became so great that many in Europe realized that if they could learn how to make porcelain themselves, they would become very rich. But no one got close, and the method for making porcelain remained a jealously guarded secret known only to the Chinese, despite the Europeans sending spies to China to find it out. It wasn’t for five hu...

Industrial espionage was rife, but it still took another fifty years for the British to come up with their own version of porcelain, using local ingredients, called “bone china porcelain.” And it was from this material that the tea set given to my parents as a wedding gift was made.

On Earth, ninety-four different types of atoms naturally exist, but eight of these elements make up 98.8 percent of the mass of the Earth: iron, oxygen, silicon, magnesium, sulfur, nickel, calcium, and aluminum. The rest are technically trace elements, including carbon.

even with a very restricted set of atomic ingredients you can create materials with wildly different material properties.