How is salt harvested?
There are essentially three ways to obtain table salt.
Salt can be mined.
That’s what’s done for Kosher salt, which is mined in Michigan’s Lower Peninsula, a salt that’s often recommended in cookbooks. Mining is pretty much the process you imagine. It takes place underground, there are big machines and a lot of noise. Mined salt is purified and often has additives to prevent clumping. Iodine is also added, a public health initiative to prevent goiters. Tasted next to sea salt, I often find mined salt to have bitter, metallic flavors.
Salt can be boiled out of seawater.
This is what’s often done in cloudy, moist, coastal places. Seawater is slowly cooked, like soup stock, until the salt naturally crystallizes. The crystals form pyramid structures that have a satisfying crunch. This salt is not treated any further and can often be a startling shade of bright white.
Salt can be dried out of seawater by the sun in shallow pools.
This way has the most history. Given that it’s almost entirely “solar powered,” it’s the most natural, environmentally sensitive process. Typically, nothing is added. Its color can range from near grey to titanium white depending on the makeup of the local water.
Traditional salts like these can have great differences from one to another. While salt is primarily sodium chloride, the other elements present in the sea, some of which make it into the salt, add flavors. From Portugal’s Algarve to Sicily’s Trapani to France’s Brittany, the colors and flavors of the salts gathered in each area are very different. There are also textural differences, usually the result of grain size or harvest method.
Sea salt’s typical harvest method is shovel and wheelbarrow. The pools dry and look a bit like frozen ponds. The salt gatherers chip into it like they would into ice. However, in some areas, like Algarve and Brittany, there is a second method. Gatherers use rakes to collect the salt off the top of the water before it solidifies. This is called the flower of the salt (fleur de sel in French, flor de sal in Portuguese). It has a texture like crunchy snowflakes and is prized for its delicacy.