The Knowledge: How to Rebuild Our World From Scratch (11 page)

Finally, we’ll look at how the mastery of temperature—using extremes of heat and cold—has become invaluable for food preservation.

The preservation techniques used throughout history—drying, salting, pickling, smoking—are pretty effective but often change the
flavor of the food, and are not perfect in maintaining the nutritional content. A new method was devised by a French confectioner in the early years of the nineteenth century: sealing the food in glass jars with a cork stopper and wax, and then standing the jars in hot water for several hours. Soon after, airtight metal cans began to be used (the reason that we use tin cans, or at least tin-coated steel, today is that this is one of the few metals that will not corrode with the acidity of foods).
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Encouragingly for an accelerated reboot, there was no missing prerequisite technology that prevented the development of canned food centuries earlier in our history—perhaps even skilled Roman glassworkers could have made reliably sealable airtight vessels—so survivors can start canning food soon after the Fall.

The key principle of the canning process is to inactivate microbes already present using heat and apply an airtight seal to prevent any more from recontaminating the food to cause decomposition. A related procedure, called pasteurization, involves briefly heating foodstuffs to 65–70°C so as to deactivate spoilage or pathogenic microbes. This has been particularly effective in treating milk (without curdling it) to prevent the transmission of tuberculosis or gastrointestinal diseases to humans. For the safest preservation, food that isn’t already acidic or pickled should be pressure-canned, exposing it to temperatures above the normal boiling point, as this completely sterilizes the contents and kills even temperature-resistant spores of microbes like those responsible for botulism.

That’s how high temperatures can be used to preserve vital stockpiles of food for many years. But what about the cold?

As temperature drops, the activity and reproduction of microbes are slowed, as are the chemical reactions that turn butter rancid and
soften fresh fruit. The preserving effect of low temperature has been known for a long time. At least 3,000 years ago the Chinese were gathering ice in winter to preserve food in caves through the year, and in the 1800s Norway was a major exporter of its ice to Western Europe. But being able to artificially create cold is a fundamental advance of modern civilization—and is much trickier to pull off than generating heat. The application of the principles known as the gas laws to create refrigerators is handy for keeping fresh food from spoiling rapidly and for freezing for long-term preservation, but can also be applied to the safe storage of hospital stocks of blood or transportation of vaccines, as well as to building air conditioners or distilling air to produce liquid oxygen. We’ll take quite a detailed look at how refrigerators work, because it also illustrates an interesting point about the adoption of technology and how a recovering society could end up taking very different paths from our own.

The key operating principle behind refrigeration is that as a liquid vaporizes to gas, it removes the heat required for that transition from its surroundings. This is why our bodies perspire to keep cool, and a low-tech solution for refrigeration is essentially a sweating clay tub. The
Zeer pot, common in Africa, consists of a lidded clay tub inside an unglazed larger one, with the gap between them filled with damp sand. As the moisture evaporates it draws heat out of the inner container, lowering its temperature, so the Zeer pot can postpone the spoilage of fruits or vegetables at market by a week or more.

All mechanical refrigerators work on the same basic principle: controlling the vaporization and recondensation of a “refrigerant.” Vaporization (boiling) requires heat energy, whereas condensation releases that thermal energy. If you arrange for the vaporization part of the cycle to happen in pipes within an insulated box, you draw heat out of this closed space and so cool the insides, allowing you to export that heat out into the surrounding air through black radiator fins at the back of the appliance.

Practically all modern refrigerators force the condensation step—returning the refrigerant to a liquid so that it can be vaporized again and remove more heat from the compartment—by using an electric compressor pump.
But there are alternative methods, the simplest of which is known as an absorption refrigerator (Albert Einstein himself co-invented one version). In this system, a refrigerant such as ammonia is condensed not by pressurizing it but simply by allowing it to dissolve, or be absorbed, into water. The refrigerant is returned to the cycle by heating the ammonia-water mixture to separate the ammonia, which has a far lower boiling point (the same principle of distillation we saw
here
), using either a gas flame, an electric filament, or just the Sun’s warmth. In this way, an absorption refrigerator ingeniously uses heat to keep things cool. Indeed, without the need of an electric motor for the compressor pump, this design has no moving parts, thus slashing the need for maintenance and the risk of breakdown. And it operates silently.

If history is just one damn thing after another, then the history of technology is just one damn invention after another: a succession of gadgets each beating off inferior rivals. Or is it? Reality is rarely that simple, and we must remember that the history of technology is written by the victors: successful innovations give the illusion of a linear sequence of stepping stones, while the losers fade into obscurity and are forgotten. But what determines the success of an invention is not always necessarily superiority of function.

In our history, both compressor and absorption designs for refrigeration were being developed around the same time, but it is the compressor variety that achieved commercial success and now dominates. This is largely due to encouragement by nascent electricity companies keen to ensure growth in demand for their product. Thus the widespread absence of absorber refrigerators today (except for gas-fueled designs for recreation vehicles, where the ability to run without an electrical supply is paramount) is not due to any intrinsic inferiority of the
design itself, but far more due to contingencies of social or economic factors. The only products that become available are those the manufacturer believes can be sold at the highest profit margin, and much of that depends on the infrastructure that already happens to be in place. So the reason that the fridge in your kitchen hums—uses an electric compressor rather than a silent absorption design—has less to do with the technological superiority of that mechanism than with quirks of the socioeconomic environment in the early 1900s, when the solution became “locked in.” A recovering post-apocalyptic society may well take a different trajectory in its development.

We’ve seen how pottery used for cooking and fermentation aids digestion like an external stomach, and the millstone serves as an extension of our molars. In the same way, clothing is another application of technology to enhance the natural biological capability of our own bodies, improving our ability to retain body heat and so spread far beyond the East African savanna.

Until only about seventy years ago—the blink of an eye in the timescale of civilization—we clothed ourselves with natural animal and plant products. The first synthetic fiber, nylon, did not appear until the outbreak of the Second World War. The degree of sophistication in organic chemistry required for re-creating these polymers will remain beyond the grasp of a rebooting society for quite a while. There is therefore a deep link between how we have traditionally fed and clothed ourselves—agriculture involving domesticated plant and animal species provides a reliable food source, but also the fibers that are twisted into cordage or woven into fabrics, and the skin that is turned into leather. And the techniques of spinning and weaving underpin many other fundamental functions of civilization: cord for binding,
ropes for construction cranes, canvas for the sails of a ship or the blades of a windmill.

Once the hand-me-down clothes from the past civilization have worn out, the rebooting society will once again need to gather suitable fibers from the natural world. Plant sources include the pithy stems of hemp, jute, and flax (linen); the leaves of sisal, yucca, and agave; and the fluffy fibers surrounding the seeds of cotton or kapok. Animal fibers can be gathered from the hair of pretty much any furry mammal, although sheep or alpaca wool is most common, and one prevalent insect source is the cocoon of the
Bombyx mori
moth: silk. In this way, both a woolly hat and a fine silk dress are composed of protein not much different from steak, whereas a linen jacket or cotton shirt is made of the same basic stuff as newspaper: sugar molecules strung together into cellulose plant fibers.

So what are the basics required for transforming clumps of natural fiber plucked from cotton or shorn from sheep into clothes to keep you alive? We’ll start first with the more rudimentary, entry-level techniques, before looking at how these were overhauled by the world-changing mechanization that began with the Industrial Revolution in eighteenth-century Britain. Our focus will be mainly on wool, which in the event of a cataclysm will remain obtainable over a much wider geographical range than alternatives like cotton or silk.

Once the shorn wool has been picked clean of debris and bits of vegetation, it is washed in warm soapy water to remove much of the grease in the fibers. It then needs to be carded: repeatedly combed between two paddles studded with pins, to break up and thin out a tight wad of wool into a soft, fluffy roll of straightened and aligned fibers. This prepared “roving” is now ready for spinning.

The goal of spinning is to turn a fluff of short fibers into a length of strong thread. You can achieve this without any tools at all, by gently tugging at the roving to pull away a loose tangle of fibers and then
twisting this between the tips of your finger and thumb into a thin thread. Although it’s possible to do this by using your hands alone, it is awfully time-consuming, so ideally you would want to employ some technology to make the task easier. The spinning wheel is able to perform both important functions: drawing out the roving into a thin strand and then spinning it into a sturdy yarn.

The large wheel is operated by hand, or by your foot working a treadle, and is linked by a belt or cord to more rapidly turn the front spindle shaft. The key mechanism here, the spindle flyer, was conceived by Leonardo da Vinci around 1500, and is the rare brainchild of the inventor that was actually constructed during his lifetime. The U-shaped flyer rotates slightly faster than the spindle, and the strands being spun are guided through a row of hooks along one of the arms before slipping off the end and wrapping around the central spindle. This ingeniously simple design is able to simultaneously impart twist to the fibers and wind them into a reel of thread to be used later. Even so, making enough thread with a spinning wheel is so time-consuming that historically it was performed only by young girls or older unmarried women—spinsters.

SPINNING WHEEL, SHOWING THE ROVING BEING FED THROUGH THE ROTATING SPINDLE FLYER ARMS SO THAT IT IS TWISTED INTO THREAD AS IT WINDS ONTO THE SPOOL.

To make a single thread stronger, you can twist it with a second to create a two-ply twine; and, more
important, if you twist them in the direction opposite to how they were originally spun, the two intertwined strands will naturally lock together and not unravel. You can repeat this combination process to make ropes thicker than your arm and able to support tons of weight, all from fibers that are very weak individually and no more than a few inches long.

The biggest demand for your spun yarns, however, will be in producing fabrics. Take a close look at the weave of the clothes you’re wearing right now. Shirts often have particularly fine weaves, so you’ll see the pattern more obviously in a woolen jacket, a T-shirt, or rugged trousers like jeans. You’ll also notice a variety of different patterns used in curtains and blankets, bedsheets, duvets, sofa covers, or carpets.

We’ll ignore the exact pattern for the time being, but it should be clear that any cloth or fabric is made up of two sets of fibers, at right angles to each other, and interwoven over and under each other. The first set, called the warp fibers, are the main structural components of a fabric and so must be stronger—try two- or four-ply yarns—than the weft fibers that fill in between the parallel lines of the warp and bind them all together.

Weaving is performed on a loom, and the crucial function of any loom is to hold the warp threads in taut parallel lines and then raise or lower different groups of these fibers so that the weft can be threaded between them. The most rudimentary looms consist of no more than two rods—one tied to a tree and the other the ground—holding the warp fibers taut between them, but greater sophistication is offered by a loom with a horizontal frame bearing the warp.

Setting up the loom involves wrapping a continuous twine tightly back and forth straight along its length, creating a grating of neatly parallel warp lines. The crucial component of the loom is the heddle, the device that allows you to separate the warp threads by raising or lowering a subset of them (we’ll come back to this in a second). The weft is then passed across the loom through the gap, or shed, that is created between the parted warps; the set of warp fibers that are raised is changed and then the weft brought back across again, building up the mesh of the fabric one row at a time.

WEAVING LOOM. THE HEDDLES ARE LIFTING A SET OF WARP FIBERS TO ALLOW THE WEFT TO BE PASSED ACROSS THROUGH THE GAP.

Varying the sequence with which subsets of the warp threads are raised changes the interleaving pattern of the weft and gives you different styles of fabric. In the most basic pattern, the plain weave, the weft simply passes over and then under a single warp thread each time to create an even grid of interwoven links—this is the standard weave for linen. A clever design for a heddle able to achieve this is a long board with a row of alternating narrow slots and holes, each threaded with an individual warp fiber. When this rigid heddle is raised or
lowered only the warp fibers caught in the holes move with it, while those running through a tall slit are unaffected as the heddle slides around them, allowing the weft to be passed under and then over alternating warps.

More complicated weaving patterns demand more complicated heddles than the rigid board. One very versatile system is a series of strings dangling in a row from a horizontal shaft, each with a knotted-loop or metal-eyelet heddle at the same height, so that only those warp fibers threaded through the heddles are lifted when the shaft is raised. Each group of warp fibers is controlled by its own raisable shaft, and the more complex the weaving pattern, the greater the number of separate shafts operating the heddles that is required to adequately control the sequence of warp movements. For example, in a twill weave the weft passes over several warp threads at once (called a float), with the floats staggered between rows to give a diagonal pattern. The reduced number of interlacings, as the warp and weft float over each other, gives a twill weave extra flexibility and comfort, but also allows the yarns to be packed more tightly together, making the fabric more durable. Denim, for example, is a 3/1 twill, whereby the warp and weft threads float for three and then cross over for one.

Whether your garments are stitched from leather or woven fabric, the next problem is how to attach them securely to your body. Disregarding zippers and velcro as too complex to be fabricated by a rebooting civilization, you’re low on options for easily reversible fastenings. The best low-tech solution never occurred to any of the ancient or classical civilizations, yet is now so ubiquitous it has become seemingly invisible. Astoundingly, the humble button didn’t become common in Europe until the mid-1300s. Indeed, it never was developed by Eastern cultures, and the Japanese were absolutely delighted when they first saw buttons sported by Portuguese traders. Despite the simplicity of its design, the new capability offered by
the button is transformative.
With an easily manufactured and readily reversible fastening, clothes do not need to be loose-fitting and formless so they can be pulled over the top of your head. Instead, they can be put on and then buttoned up at the front, and can be designed to be snugly fitted and comfortable: a true revolution in fashion.

Later in the reboot, once the post-apocalyptic population has begun to grow, there will be mounting pressure to begin automating the repetitive and time-consuming processes involved in making fabrics, maximizing the production rate while minimizing the labor required. However, you’ll find that both the automation of the different stages—carding, spinning, and weaving—and the application of mechanical power will be much more difficult than for, say, milling grain or pounding wood pulp for paper. Many of the procedures involved in fabric production are exceedingly delicate and suited to the nimble action of fingers, such as spinning a fine thread without snapping it; others, like weaving, demand a complex sequence of actions that must happen at precisely the right moment. All of this is hard to reproduce satisfactorily with rudimentary mechanisms.

The key advance over the basic weaving loom that I described was the invention of the flying shuttle. The simplest way to transfer the weft yarn through the shed gap between raised and lowered warp fibers is by passing a reel of thread from one hand to the other across the loom. But this is a slow action, and also limits the breadth of the fabric to that which can be comfortably reached with your arms. The flying shuttle is a reel of thread encased within a heavy, boat-shaped block that is jerked by a string from side to side of the loom along a smooth runner, playing out weft as it races across. Not only does this innovation allow the weaver to work on a much wider swath of warp fibers, it also greatly accelerates the weaving process and allows the loom to become entirely mechanized, powered by a waterwheel, steam engine, or electric motor, thereby enabling a single weaver to attend to many
machines simultaneously. Early power looms could complete a weft row every second, and modern machines convey the weft across the loom more than over 60 miles per hour.

As well as producing food and clothing for yourself, a top priority will be restoring the supply of all the natural and derived substances that are crucial for supporting civilization. Here too the goal is for the post-apocalyptic survivors to learn how to create things for themselves, rather than scavenging from the carcass of our dead society. So let’s look now at how to reboot a chemical industry from scratch.