Sea Salt Products

Strip the water out of a kilogram of average seawater and about thirty-five grams of solids are left; roughly three quarters of that is sodium chloride. The remaining fifth or so is where two sea salts stop being interchangeable. That residue decides how the salt cakes in a hopper, whether it tastes sharp or round, how much bittern clings to the crystal after harvest, and whether a magnesium plant downstream has anything worth running.

Eata Marisource supplies the whole solids line out of seawater, not just the white cubic part. Solar sea salt in coarse, fine and flake forms; washed and unwashed grades with documented bittern carry-over; the magnesium and potassium salts that come out of the mother liquor after halite stops crystallising; precipitated magnesium hydroxide; and chemically defined salt blends built for laboratory and corrosion work where reproducibility matters more than provenance. Everything below is written so a buyer can tell which of those they actually need.

01 Evaporation Is a Separation Column Run by Weather

A solar salt works is not a single operation; it is a string of reservoirs in which seawater becomes steadily saltier and drops minerals in a fixed order. Concentration is usually expressed as a multiple of original seawater, and each threshold marks the moment another solid appears:

The last row is where behaviour surprises newcomers. Bittern salts precipitate only in the final couple of percent of evaporation, and by then the liquor is so dense and viscous that it feels faintly oily between the fingers. Working plants never let it get that far in the harvest pans. A typical modern operation concentrates brine to about 25.5 percent before it enters the crystallisers; above that halite begins to precipitate, and by roughly 29.5 percent around three quarters of the sodium chloride in the pans has come down. Past that point magnesium and potassium salts start to appear, and the remaining liquor is drained away as bittern rather than contaminating the crop.

02 Where the Cut Is Made Decides the Grade

Quality in sea salt is largely a timing decision. Pans are usually run as a cascade, and the fraction each one contributes is not the same: the first, contaminated with residual calcium sulfate, is coarser and harder; later pans run hotter in magnesium sulfate and give salt that dries damp and cakes. Pulling the harvest earlier gives a cleaner crystal and lower yield; running longer recovers more sodium chloride and hands you the magnesium you will later have to wash out.

• The Cut: the sodium chloride harvest window described above — early pours carry gypsum, late pours carry magnesium sulfate, and the difference is visible in how the finished salt flows.
• The Wash: harvested crystal is rinsed with saturated brine rather than fresh water, which strips the bittern film clinging to each grain without dissolving the product itself.
• The Cure: washed salt leaves the pans holding roughly thirty percent moisture; several weeks of drained storage brings that down to about one and a half to two percent, and the number matters because it is the difference between a free-flowing product and a solidified one.
• The Tail: the final specific gravity of the spent liquor determines what the bittern is worth — anywhere around 1.25 to 1.26 and it becomes feedstock for potash, bromine, magnesium sulfate and magnesium chloride instead of a disposal problem.

A coastal solar salt works viewed from the air, the ponds grading from green through amber to pink.

Brine concentrated in a glass dish, with a rim of crust and first cubic crystals at the surface.

03 What Leaves the Works

One detail separates the profitable works from the marginal one. Raising pH to about eleven throws magnesium out of solution as hydroxide, but calcium interferes with that precipitation and must be removed first — usually by dosing carbonate ahead of the hydroxide step. Binary operations routinely recover close to ninety percent or more of both calcium and magnesium from concentrate this way, turning what used to be a waste stream into two saleable solids. The same logic applies to bromide: seawater carries roughly sixty-five milligrams per litre, which is far too dilute to work with directly, but after crystallisation removes the sodium chloride the same bromide sits in a liquor concentrated enough for oxidative stripping.

Irregular hollow flake sea salt crystals heaped in a shallow dish.

Broken translucent magnesium chloride crystals showing glassy fracture faces.

04 Choosing Between Natural and Defined

A recurring question from laboratories is whether to use harvested sea salt or a formulated mixture. The honest answer depends entirely on what has to repeat. Natural salt carries the whole trace element fingerprint of its source, which is exactly what certain culture and fermentation programmes want and exactly what makes it awkward elsewhere. A defined blend — sodium chloride near 23.9 grams per kilogram of solution, sodium sulfate near 4.0, potassium chloride 0.68, bicarbonate 0.20, bromide 0.10, boric acid 0.026, fluoride 0.003, magnesium and calcium added as hydrated chloride solutions — was designed to be batch-identical. Standard immersion, alternate-immersion and crevice corrosion methods rely on that identity and specifically forbid the nutrient and trace additions that marine-life formulations use, because those additives create organic films and variable redox chemistry. Conversely, anything keeping animals or algae needs the trace iron, iodine, molybdenum and zinc and a carbonate buffer holding pH near 8.2. Pick first, then buy.

05 Where the Tonnage Goes

• Food processing: seasoning, curing, brining and dough; sodium reduction research leans on potassium and magnesium blends whose behaviour in a matrix is nothing like pure halite.
• Process chemistry: cheap, defined osmotic pressure and ionic strength — brine systems, salting-out steps and chromatography elution all consume salt by the pallet.
• Chlor-alkali feed: sodium chloride is the cheapest source of both sodium and chlorine in the chemical industry, but not in the condition it arrives: electrolytic duty calls for brine polished far beyond what leaves a crystalliser, and we supply either the polished intermediate or the route to it.
• Heritage industrial: several old trades still depend on the properties of cheap chloride: curing hides, exhausting dye onto fibre in the dyebath, and regenerating the resin in water softeners that trade sodium for the calcium and magnesium responsible for hardness.
• Winter roads: snow and ice control is the largest volume outlet in cold climates, where purity requirements invert — growers care about insolubles that clog spreaders, not about magnesium.
• Agriculture: magnesium and potassium are plant nutrients in their own right, and deficiency correction on light soils accounts for a steady industrial demand for sulfate and chloride salts.

A white bulk salt stockpile filling a covered storage shed.

Stacked cubic halite crystals with growth terraces visible on the faces.

06 Certificates, Packing and Storage

Salt is easy to analyse and easy to argue about, so the certificate states the basis explicitly — as-received or dry, which changes every number by the moisture content. Standard reporting covers:

• sodium chloride by argentometric titration or calculated from full ion balance, with the basis stated;
• moisture, water-insolubles and the residual calcium, magnesium, sulfate and potassium that define grade behaviour;
• particle size distribution and poured bulk density for anything running through dosing equipment;
• heavy metals, including the elements that follow iron-rich geology rather than seawater chemistry;
• flow behaviour and caking tendency after accelerated humidity exposure, for hygroscopic magnesium salts especially.

Packing follows the chemistry. Halite is forgiving and ships in bulk, big-bags or paper sacks. Hydrated magnesium chloride is not — it pulls water from air and will dissolve in its own package unless sealed against humidity, so those grades go out in lined bags or closed drums with a stated storage window and are quoted on dry basis to keep the numbers honest. Defined blends are packed in small lots with the weighed composition on the analysis rather than a generic description.

07 Made to a Purpose Rather Than Harvested on Impulse

Because every grade above differs only by where the crystallisation was stopped and how the liquor was treated afterwards, most of what we do is tuning rather than discovery. We will set a harvest cut for a residual magnesium target; produce a washed grade clean enough for a dyehouse operation or leave it unwashed because the bittern residue is the point; crystallise the bittern down a particular branch to favour sulfate or chloride; build a replacement blend matching a legacy composition your process was validated against; or supply the purified intermediate when the destination is an electrolytic cell rather than a formulation tank. Tell us the matrix and the analytical method your team trusts, and we will quote against those numbers rather than against a generic specification sheet.

Eata Marisource moves sea salt products worldwide for research and industrial programmes. Ask for the current lot analysis, a sample drawn against your target specification, or a quotation on a campaign basis.

For Research or Industrial Raw Materials, Not For Personal Medical Use!