In interesting fact, the Japanese government shut down the making of salt from 1905 to 1997. The government decreed salt making to be its sole domain, partly to develop the domestic salt industry and partly to fund the Russo-Japanese War of 1904-05.
Fortunately salt makers in Japan are returning to their traditional roots. Moshioyaki, an ancient method dating back to the first half of the Kofun Period (220-552), is thought to be one of the oldest salt-making techniques in Japan. Moshioyaki requires two ingredients, concentrated seawater and hondawara seaweed.
modern versions of moshio salt are made by boiling down concentrated seawater in steel vats with a large muslin bag full of sun-dried hondawara seaweed to extract varying salt grades. First seawater is pumped up into a vat to settle for a few days, then the water is pumped out leaving the large particles at the bottom. Then the water is “showered” for 1-2 weeks to remove calcium. During this process water trickles down fine mesh synthetic nets onto corrugated plastic gutters. As the water is cycled back into the shower system, calcium deposits to the gutters. The now concentrated water is heated and as the water evaporates, the resulting wet salt is placed into muslin bags and left it to dry out naturally.
moshio salt has been gaining popularity in restaurants throughout Japan and serves as an excellent example of how seaweeds can transform something so simple into something richer.