Material World: The Six Raw Materials That Shape Modern Civilization

by Ed Conway

Mix this salt with a tiny fraction of sulphur and charcoal dust and you have gunpowder. But the problem with saltpetre was that for most of history it was frustratingly difficult to find. For hundreds of years, the main source was fetid organic matter, most notably rotting meat and urine. For a while military leaders of the time were disproportionately concerned with dung heaps and old, abandoned privies. Men were dispatched around medieval kingdoms on the hunt for patches of putrid earth. Having identified and tasted a patch for quality, they would dig up the stinking ground, boil it, strain it and evaporate it to produce precious flakes of saltpetre. If you do a job you don’t much enjoy, you can always console yourself that you were not one of these dung collectors—petermen as they called them in England—who had to contend not merely with a disgusting living, but also with near universal unpopularity.