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GREENHOUSE EVAPORATED SALTS

In rainy climates where open-air solar evaporation is not possible, greenhouses can be used to help evaporation and shield from rain. In the calm air of a greenhouse, crystals are free to follow their hearts. Some will form as fleur de sel. Left undisturbed, this small grain may create a dimple in the water as it grows, clinging by surface tension to the water’s surface. Along the outer edge of this dimple, more crystals form, until the salt becomes a small inverted pyramid, floating like an ice cream cone in the water. Skimming the crystals from the water at this point produces flake salt. If crystals continue to grow along the rim until they sink, the flakes continue to grow until eventually sel gris results; if crystallization is allowed to continue for some time, a thick crust will form and traditional salt can be harvested.

The principles for making salt in greenhouses are much the same, but space constraints dictate very different shapes and sizes of evaporating pans. Some salts are evaporated and crystallized in the same pan, in batches. Others are made using one or a series of evaporators before the water is passed to the crystallizing pans. Such techniques generally employ mechanical pumps to move brine from one pan to the next.

Some salt makers argue that greenhouse evaporated salts are actually purer and cleaner than open-air salts. Naturally occurring pollens, leaves, and insects can be excluded from the salt-making process by taking the whole affair indoors. Greenhouse evaporators can also be used to shield against acid rain or airborne pollution in vulnerable areas.

Some salt makers take advantage of the environment of the greenhouse to purify the water using more advanced technologies than those of the traditional method of holding seawater in a vasière. Reverse osmosis processes are used by some. Ultraviolet light is used by others. However, because these salts can be fed through evaporators and crystallizers made of metal or plastic, they lack the clay and other mineral solubles that can characterize open-air solar salts.

Some greenhouse techniques don’t use pans at all. The Japanese, for example, have developed vertical evaporators. One example of this involves hanging bamboo mats from the ceiling of a greenhouse, spraying seawater on them, and letting the water drip down, evaporating as it falls. The brine is then collected from the bottom and again sprayed on the mats. This process is repeated until the brine is saturated and crystallization takes place. Other saltworks feature towers. Bamboo branches may be suspended from the ceiling to increase the surface area, and the brine is pumped to the top of the tower, allowed to trickle down the branches to the bottom, and then pumped back to the top. Holes in the walls to allow wind to blow through, evaporating the brine within.

THE LEGACY OF SALT

It is the most unlikely juxtaposition imaginable: uninspired, barren apartment buildings hunching over narrow, hastily constructed roads and weeds growing between buckled concrete—just across the road from well-maintained saltworks from the Roman era. Saltmaking is a unique economic force for the preservation of sensitive natural environments. The salt fields of San Fernando, near the ancient Phoenician seaport of Cádiz in modern-day Andalusia, Spain, have seen dramatic changes brought on by nature and man’s agricultural activities for tens of centuries. Legend has it that the Greek dynamo Hercules founded Cádiz after completing his tenth labor, slaying the three-bodied monster Geryon.

The city is considered the oldest continuously inhabited settlement on the Iberian peninsula, originally founded by those intrepid salt wheelers and dealers, the Phoenicians, in 1100 BCE. At the time, there was nothing but open bay, some tidal marshes, and reefs made of shells and sandstone. The Romans knew a good thing when they saw it, and set up a number of saltworks throughout the bay in about 500 CE. The region