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By Root 836 0

important factor is climate. Where it can take more than forty days for salt water to evaporate enough to precipitate crystallization in cool, damp climates of France, it can take less than five days in hot, dry climates of Australia. The techniques used from region to region have more in common than they do differences, however, and the most advanced are highly efficient, making optimal use of sun, wind, and tide.

There are no better exemplars of the absolute mastery of salt making than the paludiers (salt makers) south of Brittany, who have developed exquisitely refined techniques to maximize the quality of salt production in their climate. Perfected more than a thousand years ago, Breton salt making has been practiced continuously and in the same way since at least medieval times, using four sources of renewable energy—none of them mechanical—to convert seawater into salt: sun, wind, moon, and human labor. The layout of the Breton salt pans on France’s Atlantic coast exhibits astonishingly sophisticated hydraulic engineering. A series of holding ponds, evaporating basins, and crystallization pans are dug into a salt marsh, each arranged slightly lower than the next, so that water is fed by gravity from collection pond to evaporation basin to crystallizing pan. The first holding pond is at an elevation just below sea level at high tide. The last is set just above sea level at low tide.

The twice-daily surge and retreat of the tides irrigate the natural salt marsh with salt water via a manmade canal called an étier. Twice each month, there’s an especially high tide known as the fortnightly tide. When a fortnightly tide occurs during the salt-making season, the paludier opens a trap and lets water flow from the étier into a large decanting pond called the vasière, or silt-pond. The trap is closed before the tide goes out, leaving the salt maker with a large pond of water at the highest elevation of the saltworks. The vasière thus frees the salt maker of the need to wait for high tides to replenish the source water. Vasières are typically a few feet deep, and the water temperature will usually reach about 72°F. The salinity of the water will rise a little while it’s in the vasière, from about 3.5 percent to about 4 percent.

All of the evaporating basins in the saline, or salt field, have names specific to western France’s salt-making traditions—cobiers, fares, adernes, oeillets—with some terms in this lexicon varying from town to town. Each basin provides a carefully calibrated ratio of volume to surface area to allow for the proper rate of evaporation.

As the name vasière implies (vas means “muck” or “mud”), part of the function of a vasière is to allow organic and inorganic matter to settle out of the seawater as it sits. After the water has stood for several days, the salt maker opens a gate to allow the water to flow into the first of a series of specially designed basins that make up the salt field.

The water from the vasière flows down slowly into a succession of four types of basins linked to it. The first of these is the cobier. While the vasière is basically a pond dug from the surrounding marsh, the cobier and all subsequent basins are meticulously excavated from the magnificent pale gray porcelain clay bottoms of the region’s marshes. The number and size of the cobiers in a saltworks are dependent on the salinity and temperature of the water. About 20 percent of the water will evaporate here. Salinity will reach about 5 percent and the water will warm to about 77°F. Brine is defined as saltwater that has greater than fifty parts per thousand salt, so it’s at this point the seawater officially becomes brine, or saumure.

Next, in the fares, most evaporation occurs. Fares can take up half or more of the total area of the salt farm. The fares are cut by a number of talus, the banks and borders fashioned from clay that define the basins and channels of the salt farm. The talus in the fares form chicanes—tight switchback turns—so that the water meanders from one fare to the next, circulating slowly in a highly