Salt

Shio

Since the Jōmon Period (13,000–300 BCE), salt in Japan has been produced from seawater using a method in which a concentrated brine solution (about 20%) is obtained, and this liquid is then boiled until it crystallizes. This process developed in response to the natural conditions of the archipelago, where there are no rock salt deposits—formations of sodium chloride resulting from the evaporation of ancient seas and lakes—nor salt lakes, and where the humid and rainy climate hinders direct solar evaporation. Thus, since ancient times, the sea has been the primary source of this mineral in Japan.

Over the centuries, salt became an essential resource not only for food but also for economic and territorial organization. Routes known as Shio no Michi (salt roads) played a key role in feudal Japan, especially during the Edo period (1603–1868), connecting coastal production regions to inland areas. The most famous of these, the Chikuni Kaidō, connected the Sea of Japan from the city of Niigata to Matsumoto Castle in Nagano. This system, based on regional production and land-based distribution, declined with the establishment of the salt monopoly in the early 20th century.

The monopoly was a state-controlled system aimed at raising war funds; it regulated both the extraction of salt and the commodity’s import, preventing price fluctuations and ensuring access throughout Japan. Its official closure in 1997, as part of broader economic reforms to promote competitiveness, paved the way for the diversification of production across different regions of the country and for the revitalization of traditional and innovative methods. Among these, stands out moshio-yaki, an ancient technique in which seaweed is dried until salt crystals form on its surface; these crystals are then dissolved in seawater to produce a concentrated brine, which is subsequently boiled. Another traditional method is agehama, still practiced on the Noto Peninsula, in which seawater is spread over sandy fields to evaporate in the sun before being concentrated and heated. Irihama, on the other hand, which became widespread during the Edo period, uses fields flooded by the tides to facilitate evaporation. Today, methods such as ion-exchange membrane electrodialysis allow salt to be concentrated using electricity, reducing dependence on manual labor and weather conditions.

Salt also plays a key role in Japanese cuisine, associated not only with its use as a direct seasoning but also with the production of condiments that are characteristic of local gastronomy, such as shoyu and miso (fermented soybean paste). To make preserved vegetables, one of the most common methods of dehydration also involves the addition of salt.

Its whiteness, in fact, is caused by an optical effect: when light strikes a cluster of salt crystals that are transparent and have faceted surfaces, it is reflected and refracted in thousands of directions, and thus our eyes perceive the salt as a white mass. In any case, the white color is not a rule, but it is commonly seen in refined salt—the kind used in everyday cooking—because it involves a chemical process that removes impurities and other minerals, such as magnesium and potassium, leaving only pure sodium chloride, which is naturally a white crystalline solid. The white color also appears in sea salts obtained solely through the evaporation of seawater; however, because they still retain a range of minerals, these offer more opaque shades that can resemble beige or gray.

Beyond daily production and consumption, salt is also closely linked to spirituality. In Japan, its uses are associated with purification, cleansing the body and the environment, and protection from evil spirits, both in rituals and in offerings.

Technical advice provided by Kazuyuki Natori, President of the Japan Color Research Institute (General Incorporated Foundation), and Shoko Isawa, former professor at Tokyo Kasei Gakuin University and Ph.D. in Engineering.

Source: Special Color Dictionary Wonderful & Beautiful 888. Supervised by Teruko Sakurai. Published by Tokyo Shoseki.