The Knowledge: How to Rebuild Our World From Scratch (14 page)

So far we’ve focused mainly on alkalis, as strong varieties are relatively easy to make. Acids, their chemical counterparts, are just as common in nature, but particularly potent kinds are harder to come across than lyes and have been significantly exploited only more recently in history. We have seen how a variety of plant products can be fermented to produce alcohol, and that this ethanol can in turn be oxidized by exposure to air to produce vinegar. Acetic acid was the earliest acid available to humanity, and for the great majority of history it was also our only option. Civilization has been able to choose from a selection of alkalis—potash, soda ash, slaked lime, ammonia—but for millennia our chemical prowess was limited by wide availability of but a single weak acid.

The next acid to be exploited by humanity was
sulfuric acid. This was initially baked out of a rare glass-like mineral called vitriol, and later mass-produced by burning pure yellow sulfur with saltpeter (potassium nitrate) in steam-filled, lead-lined boxes. Today we make sulfuric acid as an offshoot of scrubbing oil and natural gas to remove the sulfur contaminants. So in a post-apocalyptic world you might be caught in the middle: unable to create this crucial, potent acid using
traditional methods, as elemental sulfur has long since been removed from surface volcanic deposits, and incapable of pulling off more advanced techniques without the specific catalyst needed.

The trick is to employ a chemical pathway that was never used industrially in our development. Sulfur dioxide gas can be baked out of common pyrite rocks (iron pyrite is notorious as fool’s gold, and pyrites also form common ores of lead and tin) and reacted with chlorine gas, which you get from the
electrolysis of brine
, using activated carbon (a highly porous form of charcoal) as a catalyst. The resulting product is a liquid called sulfuryl chloride that can be concentrated by distillation. This compound decomposes in water to form sulfuric acid and hydrogen chloride gas, which should itself be collected and dissolved in more water for hydrochloric acid. Luckily, there is also a simple chemical test for whether a rock is a pyrite mineral (a metal sulfide compound): dribble a little dilute acid on the rock, and if it fizzes and gives off the stench of rotting eggs, you’ve got what you’re after (but hydrogen sulfide gas is poisonous, so don’t sniff too much!).

Today, more sulfuric acid is manufactured than any other compound—it is the linchpin of the modern chemical industry, and will also be crucial in accelerating a reboot. Sulfuric acid is so important because it’s good at performing several different chemical functions. Not only is it potently acidic, it is also strongly dehydrating and a powerful oxidizing agent. Most of the acid synthesized today is used to produce artificial fertilizers: it dissolves phosphate rocks (or bones) to liberate the crucial plant nutrient phosphorus. But its uses are virtually limitless: preparing iron gall ink, bleaching cotton and linen, making detergents, cleaning and preparing the surface of iron and steel for further fabrication, creating lubricants and synthetic fibers, and serving as battery acid.

Once you’ve reacquired sulfuric acid, it serves as a gateway to the production of other acids. Hydrochloric acid is produced by reacting sulfuric acid with common table salt (sodium chloride), and nitric acid
comes out of the reaction with saltpeter. Nitric acid is particularly useful because it is also a very potent oxidizing agent: it can oxidize things that sulfuric acid can’t. This makes nitric acid invaluable for creating explosives as well as for preparing silver compounds for photography—two key processes that we will return to later.

MATERIALS

There was on this continent a more advanced civilization than we have now—that can’t be denied. You can look at the rubble and the rotted metal and know it. You can dig under a strip of blown sand and find their broken roadways. But where is there evidence of the kind of machines your historians tell us they had in those days? Where are the remains of self-moving carts, or flying machines?

W
ALTER
M. M
ILLER
J
R
,
A Canticle for Leibowitz
(1960)

AS IS OBVIOUS FROM THE LAST CHAPTER,
it is difficult to overstate the sheer usefulness of wood. Its chemical potential aside, timber is one of the most ancient building materials, providing beams, planks, and poles for construction. The particular qualities of different trees are suited to different applications, and there is an enormous amount of accumulated knowledge that would need to be rediscovered by a fledgling civilization after the apocalypse. For example, elm wood’s tough, interlocked fibers resist splitting, and it’s therefore ideal for cart wheels. Hickory is particularly hard and thus suitable for the gear teeth of the power mechanisms in windmills and water mills. Pine and fir trees grow exceptionally straight and tall, and so make perfect ships’ masts.

Beyond these mechanical properties, wood fires will keep the cold
at bay once central heating systems have died, and will cook your food to inactivate microbial contamination and help release nutrients. The last chapter showed how to collect the vapors anaerobically baked out of timber to yield a selection of crucial substances: feedstock for rebooting a chemical industry. We’ve also seen how the resultant charcoal is ideal for filtering drinking water once the taps have run dry and bottled water has disappeared from supermarket shelves. Wood also provides hot-burning fuel for kilns firing pottery and bricks, for making glass, and for smelting iron and steel.

Immediately after the apocalypse you’ll be able to simply occupy existing buildings, repairing and patching them up as best you can. But all uninhabited and untended buildings will inexorably decay and collapse over the first decades, and as the surviving population grows and needs new homes, you’ll probably find it much easier to construct anew than try to restore the rotting shells of the old civilization. And to do that, you’ll need to learn the basics. Brick, glass, concrete, and steel are the literal building blocks of our civilization. But they all come from the humblest of beginnings: mucky earth, soft limestone, sand, and rocky ore that we dig from the ground and transmute with fire into the most useful materials of history. We can see this process most easily with clay, which is shaped and formed while soft and malleable before being heated in a kiln into a hard ceramic. We deliberately change the properties of a substance to suit our application.

It is easy to overlook clay in our modern lives—it’s perhaps something you associate only with art lessons at school. But the truth is that pottery played an utterly pivotal role in creating the prerequisite conditions for the founding of civilization itself. Lidded receptacles fashioned out
of clay enable food to be stored; protect it from pests and vermin; allow for cooking, preservation, and fermentation; and make foodstuffs far more portable for both traveling and trade. Clay formed into blocks and then fired to make bricks also provides a fabulous building material: the fabric of towns, mills, and factories.

Clay beds are exceedingly widespread, and lie beneath the topsoil in many areas of the world. Clay is made up of very fine particles of aluminosilicate mineral—sheets of aluminum and silicon, each bound to oxygen—weathered out of rocks and often transported over great distances by rivers or glaciers before being deposited. Various kinds of clay can therefore be simply dug out of pits in the ground and formed by hand. The most rudimentary receptacle can be formed from a moist ball of clay by pinching into the middle with your thumbs and smoothing into a round bowl. But for far more control over the process, you’ll want to redevelop the potter’s wheel. The earliest kind was simply a freely rotating disk, so that the workman could turn the piece around as he worked. The “modern” potter’s wheel, at least 500 years old and perhaps much more ancient, uses a spinning flywheel, such as a heavy rounded stone, to store rotational momentum and keep the piece turning smoothly as the potter works on it. The wheel is spun up every now and then with a push or kick, or, if you can scavenge one after the Fall, an electric motor.

Dried clay is relatively durable, but ideally you want to fire it to create ceramic. At temperatures between about 300° and 800°C, the water is driven irreversibly out of the clay structure, and the mineral plates lock together but remain porous. Heat it even further, to above 900°C, and the clay particles themselves begin to fuse together, and minor impurities in the clay melt. These vitrifying compounds soak throughout the piece, and when cool they solidify into a glassy matrix, firmly fusing together the clay crystals and filling any gaps to form a hard and watertight material. Deliberately dunking the piece in such
substances before the high-temperature firing to seal the surfaces is the art of glazing. You can even just toss some salt into the kiln: the withering heat dissociates the compound, and sodium vapor mingles with the silicon in the clay to form a glassy coating (although noxious chlorine gas is released in the process). This method was historically employed as an easy way to waterproof clay pipes to be used for water distribution or sewer systems.

Fired clay is not just hard and watertight, it is also exceedingly heat-resistant. The aluminosilicate has an extremely high melting point, and since the constituents are already bonded to oxygen, the mineral does not combust when hot. Firebricks are therefore the perfect material to line kilns and furnaces. In order to contain fire, and therefore be able to technologically employ it, you need a substance that can insulate the heat inside but is also able to resist the temperature itself. This is a great example of a recovering civilization pulling itself up by its own bootstraps: baking clay in a large fire into a refractory material enables survivors to build further kilns to fire yet more bricks. The story of civilization itself has been an epic of the containment and harnessing of fire with ever greater finesse to attain ever higher temperatures: from the cooking campfire to the pottery kiln, the Bronze Age smelter, the Iron Age furnace, and the blast furnace of the Industrial Revolution—and it is refractory bricks that have enabled all of this.

Fired clay is also used very commonly as a structural material. In drier climates you can get away with building a rudimentary wall out of sun-dried mud—adobe—but this is at risk of being washed away in a heavy downpour. A far more resilient brick is made by taking a few generous handfuls of clay, squashing it into a cuboidal shape in a mold, and then baking it in a kiln to drive the chemical transformations for a hard, durable ceramic. But you’re going to need more than handfuls of clay to rebuild civilization. For a sturdy wall, the rows of bricks will need to be glued together—and for that, we come back to lime.

We saw in Chapter 5 that the first material you’re likely to need to start mining again, once the remnant commodities left behind by our current society have been depleted, is limestone. We know limestone plays a central role in synthesizing many of the crucial substances needed by a civilization. Now we’ll take a look at how the same wonder material will form the basis of rebuilding in the aftermath. Limestone blocks are useful as a construction material—as is its metamorphic product marble, formed from limestone pressure-cooked deep underground—but it is what this rock can be turned into that is so useful for rebuilding.

Slaked lime is able to transform from a spreadable paste back into a material set hard as stone. Mixed with a little sand and water, slaked lime forms mortar, which has been used to firmly stick bricks together into sturdy load-bearing walls for thousands of years. Mix it with less sand, and perhaps stir in some fibrous material like horsehair, and you have a plaster for spreading as a smooth finish on walls.

Lime mortars have been used for millennia, but it was a substance first mass-produced by the Romans that changed the nature of building. The Romans noticed that
cementum
made by mixing slaked lime with volcanic ash, known as pozzolana, or even pulverized brick or pottery, sets far more quickly than lime mortar and is several times stronger. And with the fabulously strong mineral glue that is cement, you can do far more than just stick together ordered rows of bricks. You can also bond jumbled aggregations of rocks or rubble—that is, you can make concrete. This revolution in construction technology allowed the Romans to build awe-inspiring structures such as the Collosseum and the vast bulging roof of the Pantheon in Rome, which is still the largest single-piece concrete dome in the world.

But it is another, almost magical, property of cement that really
helped build the trading and naval prowess of the Roman empire: concrete made with pozzolana or crushed earthenware sets even when completely submerged in water. Unlike lime mortar, cement is said to be hydraulic and sets along a different chemical route. The volcanic ash contains alumina and silica—already discussed above as constituents of clay—which chemically react with the slaked lime to form an exceedingly strong material as they hydrate.

Hydraulic materials led to an important technological advance. Pozzolanic cement spurred a revolution in Roman marine construction, for rather than simply sinking large stone blocks into the water, the Romans could now pour concrete for freestanding structures directly into the sea to create quays, breakwaters, seawalls, and lighthouse foundations. This technology enabled them to build ports wherever needed for military or economic reasons, including in regions with very few natural harbors, such as the north coast of Africa. Thus, Roman ships came to dominate the Mediterranean.

This crucial knowledge about strong cements, versatile concrete, and watertight plasters was nearly lost to history with the fall of the Roman Empire. No medieval sources mention cement, and the great Gothic cathedrals were built using only lime mortar. However, knowledge seems to have been preserved in some places, as hydraulic cement was used in a number of fortresses and harbors constructed throughout the Middle Ages.

But it was in 1794 that the modern method for producing cement was invented. “Ordinary Portland cement” does not exploit volcanic heat like the Roman pozzolana variety, but bakes a mixture of limestone and clay in a specialized kiln at around 1,450°C. The hard clinker produced is then ground up with a small amount of the soft, pale mineral gypsum—also used for plaster of Paris, and in setting broken limbs in a plaster cast—which helps to slow the curing process and gives you more working time with the wet cement.

Now, I know that concrete is a horrifyingly dull and gray building material, and that there have been some architectural abominations constructed with it. But let’s step back and consider for a second what truly remarkable stuff it really is. Concrete is essentially man-made rock. And the recipe is beguilingly simple: stir together one bucket of Portland cement with two buckets of sand or gravel and enough water to make a thick gloop. Pour this liquid stone into a wooden shuttering constructed to make any shape you fancy, and then wait for it to set into an incredibly hard and durable material. It’s not difficult to see why concrete allowed rapid urban regeneration following the devastation of the Second World War and is still the prime ingredient for city-building today—an icon of the modern age, even though the basic process was invented more than two millennia ago.

The problem with concrete, however, is that while it’s incredibly strong when compressed in foundations or columns, it’s very weak when under tension. It catastrophically cracks when forces act to stretch it, which stops it from being used for large structural elements like beams, bridges, or floors of multistory buildings. The solution is to embed steel rods in the concrete. Their individual material properties perfectly complement each other: the compressive strength of concrete combines with the tensile strength of steel. This
reinforced concrete was hit upon in 1853 by a plasterer who inserted straightened metal barrel hoops into concrete floor slabs as they set. And it is this final innovation that really unlocks the potential of concrete for aiding reconstruction after the apocalypse.

Concrete is a wonderfully versatile construction material, but it is ceramic bricks, with their refractory properties, that you will need to use to contain high temperatures and so achieve the skills of metallurgy.