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The harvesting technique used in the salt marshes of the Guérande peninsula was developed over a thousand years ago, probably by the monks of Landevenec, who lived in Batz sur Mer from 845. It followed from the earlier "ignigène" (evaporation by fire) method which was widespread along the French Atlantic coast, but which required more workers and the use of fire.
Harvesting can only take place once the system has reached saturation (several months heating) and with the right climate conditions - heat, wind, absence of rain. The climate to the north of the Loire River leads to a short harvesting period lasting on average from June to the beginning of September.
A harvest "salt on salt" is not possible for Guérande salt. This technique, in which the upper layer of salt is scraped off before it becomes too hard, requires the crystallisation ponds to be "lined" with salt to prevent contact with the bottom. This requires a great deal of salt, which is then lost. In Guérande, too large a part of the harvest would be sacrificed, as the average of 1.3 tonnes of salt produced by "oeillet" only represents 2 cm spread over its surface.
Further south along the coast this technique is used as it greatly simplifies harvesting, which can take place by walking in the crystallisation ponds, every 4 to 8 days, and in particular mechanically once a year.
A daily harvest directly on the clay bed is necessary for Guérande salt. Our product is therefore softer. It is this characteristic which has always given our salt its quality, and which brings to Guérande salt and flower of salt ("fleur de sel") its physical characteristics (colour, crumbly texture), chemical properties (a natural salt, richer in minerals (magnesium, calcium, potassium, oligo-elements)) and organoleptic properties (a taste without bitterness or pungency).
Already in the 18th century, it was noted that foreigners preferred it for its moisture absorption, delicious qualities, and its large crystals with strong dehydrating power which removed water from food and made brine. It was also reputed for its whiteness and the small quantity of earth particles.
The saturated sea water in the "oeillets" evaporates during the summer under the effect of the sun and wind. When the salt crystallises, we say that the marsh "is working". This phenomenon begins at the end of the morning, and we start to see small, fine, light crystals floating at the water's surface, before clumping together in a fine skin under the effect of the wind. This is flower of salt ("fleur de sel"),also called "white salt" or "thin salt". The surface crystallisation is more abundant when the water is hot, and when the temperature difference with the colder air is greater.
At the same time, as the bottom of the "oeillet" is also colder than the water, the salt crystallises on the clay. This is coarse salt, which will be finer if the water is hot.
If it is too hot for several days/weeks, the clay base becomes so hot that there is no temperature difference - crystallisation no longer occurs and the "oeillet" is covered with powder. We say that it is "cooked". This is the only moment when the salt worker wants rain to put things back in order.
Harvesting is carried out every day in summer, when the optimum conditions are come together - flower of salt "gathering" must be done as late as possible during the day, for larger quantities and a sufficiently formed "grain".
Coarse salt can be collected at any time of the day, outside of the times when the flower of salt is forming, ie. either early in the morning before it starts to form or late in the evening after harvest.
Before moving the water to harvest the coarse salt, the flower is delicately skimmed from the surface using a "lousse" (a special rake for flower of salt). Several decades ago, this work was done by women and children.
This operation, whilst delicate, is not particularly complicated, and only requires extra hands to go faster. Even a beginner can collect good quality flower of salt, and this task is often delegated. On average, an "oeillet" produces 2 kg of flower of salt per day.
Once the flower of salt has been harvested, the coarse salt can be collected from the water at the bottom or the "mother" of the marsh. Before collection, the salt worker feeds the "oeillets" with water by opening the "ademe", with water flowing through the "délivre" (small channel), which provides the brine necessary for salt formation for the next day. This operation of supplying water is called "douiller" or "dourer" from the Breton word "dour" meaning water.
The salt worker pushes the water contained in the "oeillet" (using a tool known as a "lasse" - essentially rectangular planks with a long handle), thus moving the salt to the central platform called the "ladure".
The salt is then pulled towards this platform, and hauled up to form a "ladurée" or salt pile. The operation to haul the salt out of the water onto the "ladure" was traditionally done by the salt workers, using a "boutoué" (a smaller tool made of rectangular planks and a long handle). This more strenuous task was reserved for men. The operation requires know-how, skill and physical effort - the salt's quality depends on it, and the task cannot be delegated. The gesture must be accurate, delicate and strong; the action is well codified, and few salt workers today can do it as well as those from the town of Batz ! It takes years of apprenticeship to be authorised to carry out the harvest or "take the marsh".
This coarse salt is formed of grey-coloured crystals of varied size, depending on the weather conditions.
50 to 70 kg of coarse or grey salt are harvested per day, per "oeillet".
The salt drains on the "ladure", then is transferred by wheelbarrow (in the past, the salt was carried on the head), and put into piles called "mulons" on the "trémet" (platform at the edge of the salt works).
Finally it is transported from the platforms by agricultural machines to be stored in the "salt stores" or covered silos.