Author Mark Kurlansky even spices up his quirky and engrossing narrative with a few recipes, from salted cucumbers to garum (a preserved fish liquid) to one for "mothproof ham." The latter is a reminder that in the days before refrigeration, salt was a necessity for keeping foods edible over long periods. After reading this book, you'll think differently next time you bite into a pickle, use ketchup, or follow a de-icing truck down the road in the winter. Kurlansky, who lives in New York, recently spoke with BusinessWeek's Karin Pekarchik. Here are edited excerpts from their conversation:
Q: Where did the idea for this book come from?
A: I first began thinking about the significance of salt while working on Cod, which explored the salt-cod industry. From the Middle Ages on, the European market for salt cod was virtually limitless. So was the cod, after Europeans learned of the fishing grounds in North America. But the one limitation was salt. Sea salt was needed to cure fish and, since it is made by solar evaporation, it is [more thought of as] a southern product.
The valuable fish -- cod and herring -- are northern, so northern countries, especially England, conducted foreign policy with the goal of securing southern sea-salt supplies.
Q: Can you briefly recap salt's significance as a commodity?
A: Everyone needed it, and it had no substitute. It was far more profitable to trade in salted goods -- salt fish, then olives, then ham, game, beef, and other meat, and cheese -- than to simply trade salt. Salt had the ability to turn perishable food into a durable trade commodity. For example, there was not much that could be done internationally with milk -- but a great deal could be done with cheese.
A fish is a local food -- but a salt fish is a commodity of international trade. Salt created other nonfood commodities such as textile dyes and pottery glaze, and today it has more uses than ever. [More recently] its value has declined, not because it has lost its uses but because the supply has become too easily obtained.
Q: What are the different ways that salt can be mined?
A: Sea salt is the most common [type], and it is [obtained] by pumping sea water into artificial ponds and letting the heat of the sun evaporate the water. Brine is pumped from underground springs and boiled. And rock salt is mined, crushed, and washed. There are also less common sources -- such as dried salt lakes in deserts, notably the Sahara, that are scraped up.
Salty seaside sand can be boiled, as can peat from bogs. But most of the world's salt comes from evaporated sea, brine springs, or rock-salt mines.
Q: Can you explain the significance of salt taxes?
A: Governments have always found it tempting to tax salt because everyone, rich and poor, uses it at about the same rate, so it's a natural poll tax. Throughout history, poll taxes have been very unpopular because poor and middle-class people resent paying the same tax as the wealthy. So whenever salt taxes have been attempted -- in ancient China, France, Colonial India -- it has usually led to rebellions.
Q: Sodium chloride is the salt we eat. What are some of the other uses for salt?
A: The largest single use for salt in the U.S. is for de-icing roads. It is also used in pharmaceuticals, and there are numerous refined saline solutions that are used in medicine. It is also used in textiles, papermaking, and many other industries. There are many types of salt besides sodium chloride -- potassium chloride is used for fertilizer, magnesium chloride in metalmaking. Sodium chloride for food has become one of the less-important commercial aspects of the modern salt market.
Q: What is working in a salt mine like? Can people make a decent wage at it?
A: To ask about the wages and conditions of salt workers is like asking about farmers -- it depends on the crop and the society. Salt workers in India and sub-Saharan Africa have horrible conditions. In large operations in the U.S., Germany, or France, they have [similar working conditions] as other factory workers in those countries.
Salt mines are not dangerous the way coal mines are. Sea-salt workers, to my thinking, have a more pleasant setting than [workers] in salt mines. The historic sea-salt works of the French Bay of Bourgneuf are mostly operated by individuals organized in cooperatives. While they're not getting wealthy, they enjoy a pleasant, fairly independent agricultural existence. But many of those operations are so small that they [offer] only part-time work.
Q: How much salt does a person actually need, and how much does the average person consume?
A: There is considerable debate about how much salt we need. The body contains about 250 grams, and that level needs to be maintained. People in most societies consume more salt than they need. The excess is stored in the kidneys, which should not be a health problem as long as the kidneys are healthy. Everyone seems to agree that Americans consume more salt than other people and always have. But some people say we consume as little as 10 grams a day per person, while others say it's more than 100 grams a day per person.
Q: What countries are big salt producers now?
A: The U.S. is the world's largest salt producer as well as the largest consumer. The U.S. salt industry earns more than $1 billion a year. The second-largest producer is China, then Germany, Canada, and India.
The U.S. and Canada are upstarts, though the U.S. has been an important salt producer for more than 150 years. China has always been a leader, as has India [when it was not] being manipulated by British salt interests. But the fact that France and Britain have fallen to eighth and ninth place is a historic shift, since for many centuries these two countries were leaders. And the Mediterranean, which was a major salt center from ancient times until a few hundred years ago, has considerably faded in its world salt position.
Q: Why do you collect rock salt?
A: If you find yourself traveling the world visiting salt mines, what else can you take for souvenirs? I was struck by the fact that although these rocks were, by majority, sodium chloride, which is white, they all looked very different in color and surface.