This article is an excerpt from the Shortform book guide to "Salt" by Mark Kurlansky. Shortform has the world's best summaries and analyses of books you should be reading.
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Why do we need salt? What is salt’s impact on technological and scientific innovation?
In Salt, Mark Kurlansky argues that salt played a major role in developing new innovations. To understand this, we have to look at the way salt is harvested and where to find it on Earth.
Continue reading to learn why we need salt for societal development.
Salt’s Impact on Innovation
Why do we need salt? Because salt is necessary for life and eating, people throughout history have been motivated to develop ways to harvest it. Kurlansky argues that throughout history, salt has driven technological and scientific innovation. We’ll begin article by exploring where salt is found on Earth so that we can better understand salt-harvesting innovations. Next, we’ll describe two of the main ways salt was harvested throughout history. Finally, we’ll examine how salt also played a role in other industries’ innovations.
Where Is Salt Found?
Kurlansky explains that salt is found:
- In water: Salt is found in oceans, springs, and some lakes.
- Underground: Underground salt deposits containing rock salt (salt in hard, mineral form) can span hundreds of miles. Some take the form of salt domes (mounds of salt that form when tectonic activity forces underground deposits upward).
- Above ground: Some mountains also contain large deposits of rock salt.
According to Kurlansky, for centuries, scientists have wondered and debated why the earth is so rich in salt. Today, there’s a general consensus that salt deposits on land and underground got their salt from the ocean—but scientists don’t agree on why ocean water is salty.
Innovations in Harvesting Salt
Method 1: Solar Evaporation
According to Kurlansky, the oldest and most common method of harvesting salt is relying on the sun to evaporate water from lakes and the sea. This process leaves behind salt crystals. The ancient Chinese pioneered this method: As early as 6,000 BCE, they raked and collected salt crystals that formed on lake beds in the summer. Eventually, they and others around the world started making artificial ponds by collecting seawater and lakewater on land.
In the Middle Ages, the North African Muslims were likely the first to develop a more advanced, efficient method of solar evaporation. First, they collected seawater in an artificial pond and waited for it to partially evaporate. Next, they used pumps and gates to move this water into another pond (or a series of ponds) where it would evaporate further. Finally, new water was pumped into the first pool to start the evaporation process anew. This process was efficient because it allowed for simultaneous evaporation across multiple ponds.
Today, people continue to use various methods of solar evaporation to produce salt.
Method 2: Mining
Kurlansky claims that drilling is the main way to harvest underground brine. The Chinese lay claim to the first innovation in salt drilling: Around 250 BCE, they used bamboo tubes to siphon brine out of wells. Around a millennium later, they used percussion drilling to dig deeper. This process involves a seesaw-like lever that pounds a metal rod into the ground.
In the Middle Ages, people developed a more efficient way of mining salt: solution mining. This method involves pumping water into mines, siphoning out brine, and boiling it. According to Kurlansky, modern salt producers today continue to engage in solution mining, and they evaporate the brine using machines called vacuum evaporators.
In modern times, salt drilling led to the expansion of new industries, such as the oil industry. In the early 20th century, harvesters drilling into a Texan salt dome unexpectedly hit oil, and soon, the US and other countries began extracting oil by drilling near salt.
Oil and natural gas often gather near salt because salt deposits form dense barriers around which organic material accumulates. Over time, this organic matter decomposes, becoming valuable fuel.
Other Salt-Related Innovations
According to Kurlansky, salt has also played a key role in other technological innovations beyond those related to salt harvesting. Here are several examples:
- In ancient times, Egyptians used salt to preserve bodies for mummification. (Shortform note: Today, embalmers continue to include salt in their process, along with other compounds such as formaldehyde.)
- The ancient Chinese used saltpeter (potassium nitrate) to invent gunpowder. (Shortform note: Saltpeter is no longer used in gunpowder. However, it’s still used in various products such as pesticides, fertilizers, and fireworks.)
- In the Middle Ages, people used salt for various purposes, such as glazing pottery. (Shortform note: Industrial pottery production no longer relies on salt glazing, but some potters still use this method.)
Today, people use salt to de-ice roads because salt lowers water’s freezing point. (Shortform note: Recently, several cities have instead started de-icing roads with sugar beet juice (which also lowers water’s freezing point). Some claim sugar beet juice is a more eco-friendly and cost-effective de-icer compared to salt.)
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Here's what you'll find in our full Salt summary:
- The role salt played in driving innovation, building empires, and provoking rebellions
- Why salting food isn’t just about improving its flavor
- How salt played an important role in several independence movements
