The Story of Salt

Salt is so cheap and so common today that it is hard to imagine a time when it was one of the most sought-after substances on earth. Yet for thousands of years this simple mineral was treated as a treasure: it was fought over, taxed, and carried across whole continents. Part of the reason is that human beings cannot live without it, since the body needs a small but steady supply of salt in order to work properly, and so every society has had to find some way of obtaining it. Broadly speaking, there are two sources. Near the coast, people guide seawater into shallow ponds and simply wait; as the water slowly evaporates under the sun, a crust of salt is left behind, ready to be raked up and gathered. Far from any coast, salt occurs in solid form deep underground, the dried remains of seas that vanished long ago, and there it has to be cut loose and hauled up from deep mines.

For most of human history, the greatest value of salt lay in its power to preserve food. Before refrigeration existed, there was no dependable way to stop fresh food from rotting, and a failed harvest or a long winter could bring the threat of starvation. Salt changed all this. Rubbed into cuts of meat and fish, it drew out the moisture in which bacteria thrive, so that food could be kept for months rather than days. This one property shaped the whole way people lived. It let communities store a surplus to see them through hard times, and it made long sea voyages possible, because ships could at last carry barrels of preserved food that would not spoil before land was reached.

Because it was both essential and hard to come by, salt grew immensely valuable. In certain times and places it was worth its weight in gold, handed over measure for measure for the precious metal itself. Vast trade networks arose to move it from the places where it was made to the places where it was wanted. Across the Sahara, merchants carried heavy slabs of it on caravans of camels, on journeys that might last for months and cross some of the cruellest terrain on earth. The Romans understood its worth too: their soldiers were sometimes granted a special allowance with which to buy salt, and the Latin word for this payment, salarium, is the root of the modern English word "salary". To be "worth one's salt" still means to be worth one's wages.

The value of salt also made it a perfect means for governments to raise money. Because everyone had to buy it, a tax on salt was almost impossible to escape, and rulers throughout history seized the chance. In France, a hated salt tax known as the gabelle required every person above the age of eight to buy a fixed quantity of salt every week, at a price set by the crown. It was deeply resented, and it became one of the many grievances that helped to bring about the French Revolution. The same fury broke out again in the twentieth century in India, where a British tax on salt led Mahatma Gandhi to march to the coast with thousands of followers and make salt from seawater with his own hands, in open defiance of the law.

The long reign of salt could not last. During the nineteenth century, new industrial methods made it possible to produce the mineral in enormous quantities, while at the same time the spread of refrigeration offered people a fresh way of keeping food from spoiling. Salt became cheap and plentiful, and as it did so it shed the prestige it had carried for centuries. Its role was transformed. Today only a small fraction of the salt produced around the world finds its way into food; the overwhelming majority is taken up by the chemical industry or, in colder countries, scattered across roads to melt the winter ice.

It is easy, now, to forget how precious this everyday substance once was. Yet the traces of its long reign lie all around us. In England, towns whose names end in "-wich", such as Northwich and Nantwich, grew up beside natural springs of salt water. Old roads still follow the paths once worn smooth by salt traders. And the language we speak is scattered with reminders of an age when salt stood for both wealth and survival. A mineral that once helped to raise cities and bring down governments now sits, unnoticed, in a shaker on the kitchen table.