Guest Article: Substances, by Dr. Lewis Dartnell


The Knowledge: How to Rebuild our World from Scratch is a new book out in the U.S. now, and a New York Times science bestseller. If civilization does collapse, whether it’s caused by a viral pandemic, coronal mass ejection, or financial meltdown, the break in normal services is likely to cause a great deal of panic and perhaps a severe depopulation among the unprepared. The world as we know it has ended, but what now? What can the survivors do to ensure they thrive in the long-term, and how can you begin rebuilding a proficient society over the generations? Many preppers keep a large stockpile of preserved food, defensive weapons and ammunition, and other consumables, but this won’t last forever. What do you do when it starts running out? How do you teach your children to make for themselves all that they need and their children will need?

The essence of The Knowledge is a thought experiment– an exploration of the behind-the-scenes fundamentals of society. What is the crucial science and technology behind how our modern world works and how did civilization progress over the centuries? And if you ever had to, how could you avoid another Dark Ages and reboot civilization as rapidly as possible? What could you do better the second time around?

The Knowledge takes the discussion beyond many prepper books and websites that explain important topics, like survival skills, preserving food, and weapons (such as How to Survive TEOTWAWKI) and explains all you need to know in areas like agriculture, materials, energy, and transport in order to rebuild society itself, at least as far as is possible within a single book.

Below is an excerpt of the book, exclusive to SurvivalBlog, from the section dealing with creating crucial substances for yourself.

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Even before humanity began to settle down and the first cities were founded in Mesopotamia, our lives depended on the deliberate extraction, manipulation, and exploitation of natural chemicals. Over the centuries we’ve learned new ways to interconvert between different substances, transforming those that can be most easily acquired from our surroundings into those that we need the most, and producing the raw materials with which our civilization has been built. Our success as a species has come not just from mastering farming and animal husbandry or employing tools and mechanical systems to ease labor; it also derives from the proficiency with which we can provide substances and materials with desirable qualities.

The first substance that a recovering post-apocalyptic society will need to begin mining and processing for itself, because of its multitude of functions that are absolutely critical to the fundamental operations of any civilization, is calcium carbonate. This simple compound, and the derivatives easily produced from it, can be used to revive agricultural productivity, maintain hygiene and purify drinking water, smelt metals, and make glass. It also offers a crucial construction material for rebuilding and provides key reagents for rebooting the chemical industry.

Coral and seashells are both very pure sources of calcium carbonate, as is chalk. In fact, chalk is also a biological rock: the white cliffs of Dover are essentially a 100-meter-thick slab of compacted seashells from an ancient seafloor. But the most widespread source of calcium carbonate is limestone. Luckily, limestone is relatively soft and can be broken out of a quarry face without too much trouble, using hammers, chisels, and pickaxes. Alternatively, the scavenged steel axle from a motor vehicle can be forged into a pointed end and used as a drill to repeatedly drop or pound into the rock face to create rows of holes. Ram these with wooden plugs and then keep them wet so that they swell and eventually fissure the rock. But pretty soon you’ll want to reinvent explosives (Chapter 11) and use blasting charges to replace this backbreaking labor.

Calcium carbonate itself is routinely used as “agricultural lime” to condition fields and maximize their crop productivity. It is well worth sprinkling crushed chalk or limestone on acidic soil to push the pH back toward neutral. Acidic soil decreases the availability of the crucial plant nutrients we discussed in Chapter 3, particularly phosphorus, and begins starving your crops. Liming fields helps enhance the effectiveness of any muck or chemical fertilizers you spread.

It is the chemical transformations that limestone undergoes when you heat it, however, that are particularly useful for a great range of civilization’s needs. If calcium carbonate is roasted in a sufficiently hot oven—a kiln burning at least at 900°C—the mineral decomposes to calcium oxide, liberating carbon dioxide gas. Calcium oxide is commonly known as burned lime, or quicklime. Quicklime is an extremely caustic substance, and is used in mass graves—which may well be necessary after the apocalypse—to help prevent the spread of diseases and to control odor. Another versatile substance is created by carefully reacting this burned lime with water. The name quicklime comes from the Old English, meaning “animated” or “lively,” as burned lime can react so vigorously with water, releasing boiling heat, that it seems to be alive. Chemically speaking, the extremely caustic calcium oxide is tearing the molecules of water in half to make calcium hydroxide, also called hydrated lime or slaked lime.

Hydrated lime is strongly alkaline and caustic, and has plenty of uses. If you want a clean white coating for keeping buildings cool in hot climes, mix slaked lime with chalk to make a whitewash. Slaked lime can also be used to process wastewater, helping bind tiny suspended particles together into sediment, leaving clear water, ready for further treatment. It’s also a critical ingredient for construction, as we’ll see in the next chapter. It’s fair to say that without slaked lime, we simply wouldn’t have towns and cities as we recognize them. But first, how do you actually transform rock into quicklime?

Modern lime works use rotating steel drums with oil-fired heating jets to bake quicklime, but in the post-apocalyptic world you’ll be limited to more rudimentary methods. If you’re really pulling yourself up by your bootstraps, you can roast limestone in the center of a large wood fire in a pit, crush and slake the small batches of lime produced, and use them to make a mortar suitable for building a more effective brick-lined kiln for producing lime more efficiently.

The best low-tech option for burning lime is the mixed-feed shaft kiln: essentially a tall chimney stuffed with alternating layers of fuel and limestone to be calcined. These are often built into the side of a steep hill for both structural support and added insulation. As the charge of limestone settles down through the shaft, it is first preheated and dried by the rising draft of hot air, then calcined in the combustion zone before it cools at the bottom, and the crumbling quicklime can be raked out through access ports. As the fuel burns down to ash and the quicklime spills out the bottom, you can pile in more layers of fuel and limestone at the top to keep the kiln going indefinitely.

A shallow pool of water is needed for slaking the quicklime, and you could use a salvaged bathtub. The fine particles produced will turn the water milky before gradually settling to the bottom and agglutinating as the mass absorbs more and more water. If you drain off the limewater, you’ll be left with a viscous sludge of slaked-lime putty. Limewater is used to produce gunpowder, and the slaked lime is a critical ingredient for construction: making a mineral glue for sticking together fired-clay bricks or gravel for concrete, as we’ll see in the next chapter. Another fundamental use of lime is for making soap.

Soap can be made easily from basic stuff in the natural world around you and will be an essential substance in the aftermath for averting a resurgence of preventable diseases. Health education studies in the developing world have found that nearly half of all gastrointestinal and respiratory infections can be avoided simply by regularly washing your hands.

Oils and fats are the raw material of all soaps. So, somewhat ironically, if you carelessly splash bacon fat onto your shirt cooking breakfast, the very substance you use to clean it out again can itself be derived from lard. The key step in making soap is to chemically break open, or “hydrolyze” the fatty molecules, and for this you need a potent alkali. Alkalis are the opposites of acids, and when the two meet they neutralize each other to produce water and a salt. Coated with a fur of these long soap molecules, a small droplet of oil is stabilized in the midst of the water that rejects it, and so grease can be lifted off skin or fabric and be washed away. The bottle of “invigorating, reviving, hydrating, deep clean sea splash” men’s shower gel in my bathroom lists nearly thirty ingredients. But alongside all the foaming agents, stabilizers, preservatives, gelling and thickening agents, perfumes, and colorants, the active ingredient is still a soap-like mild surfactant based on coconut, olive, palm, or castor oil.

The pressing question, therefore, is where to get alkali in a post-apocalyptic world without reagent suppliers. The good news is that survivors can revert to ancient chemical extraction techniques and the most unlikely-seeming source: ash.

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Dr. Lewis Dartnell is a research fellow at the University of Leicester, England, and the author of The Knowledge: How to Rebuild our World from Scratch, out now with Penguin Press. Explore extra material on the book’s website:

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