Lowfield Salt — solar saltworks, pans 1 to 6

Lowfield Salt · pans 1—6 · the flat behind the seawall

Coarse pan salt £6 a kilo at the gate, or £4.40 a kilo wholesale in 25 kg sacks. Fleur de sel £11 the 125 g box. Post under 30 kg is a flat £9 and leaves Tuesdays and Fridays.

Order salt or 01632 960 683 — the sluice house, most of the day

A wooden-bladed rake pushing a ridge of wet salt crystals across the flat floor of a crystalliser pan, with shallow brine standing beyond it. — Raking 6b, the morning after it was drawn down printed in the intake pan, 3.5 °Bé

Degrees Baumé, a reading of how heavy the water is with salt. It is the only number this works runs on. Everything below is the twenty-three and a half degrees between those two figures, and how long the wind takes to find them.

The colour of this page is the colour of the pan being described. It is not a decision we made about the brand. Brine changes colour as it concentrates, and we have printed the readings alongside so you can check us.

Gate reading, this morning

3.5 °Bé · 11.4 °C

Sluice opened on the flood, 05:12. Reservoir took 2,900 m³.

The intake end of the works from 300 metres: a straight feed channel running in from a sluice in the seawall, the estuary at one edge, the first shallow pans beyond. — The gate and the feed channel, from 300 m printed at 3.5 °Bé

The plan is drawn to the pans' relative areas and scrolls sideways.

The reservoir, which does not change

The reservoir is deep, shaded on its north side by the wall, and kept topped up on every spring tide. It has held 3.5 °Bé for as long as anyone has taken readings here. Nothing is harvested from it and nothing is meant to happen in it.

It is on this page for the same reason it is in the works: it is the control. The pans below have to be read against something that is not moving. If this section had shifted colour with the rest of them, the colour would have been an effect rather than a reading.

Ground colour here is identical to the gate above — same swatch, same reading, one pan apart in the works and eight weeks apart in the season.

The storage reservoir from 300 metres: one large rectangle of still dark water held inside heavy earth banks, with a short inlet pipe at a corner. — The reservoir, from 300 m printed at 3.5 °Bé

Condensers 1 and 2

3.5 → 7.0 °Bé

Half the water in the works leaves here, and it takes about five weeks of it to do so. The pans are wide and shallow — 40 cm at the sluice end, 18 cm at the far wall — because evaporation is a function of surface, not of volume.

Carbonate drops out first, at around 7. It settles as a pale scale on the floor of the pan and stays there; we sweep it in October. It is also the point at which the water stops being clear and starts being green, because the alga that tolerates this salinity has nothing left to compete with.

Losing 6 mm on a dry day with wind. Gaining 11 mm in an hour of rain. The season is the arithmetic of those two numbers.

Condensers 1 and 2 from 300 metres: two very large shallow pans divided by one long earth bank with a wooden weir box set into it. — Condensers 1 and 2, from 300 m printed at 7.0 °Bé

Pans 3 and 4, where the gypsum goes

7.0 → 16.0 °Bé

Calcium sulphate comes out of solution between 14 and 16, in clear needles you can pick up whole off the floor. This is the reason the works has six pans and not one: every mineral in seawater has a density at which it gives up, and they do not give up together.

Let the gypsum into the crystallisers and it goes into the salt as grit. Everything upstream of pan 5 exists to take something out before the sodium chloride is allowed to fall.

Pans 3 and 4 from 300 metres: two medium pans whose floors are crusted with a hard pale mineral scale under shallow water, one partly drawn down. — Pans 3 and 4, from 300 m printed at 16.0 °Bé

Pan 5 turns red at saturation

16.0 → 25.7 °Bé

Above about 22 the green alga stops coping and the water is taken over by organisms that carry carotenoid pigment as protection. The pan goes orange, then brick red, over roughly a fortnight. It is visible from the sea road and it is the only instrument here that can be read at 400 metres.

25.7 is saturation for sodium chloride. Past it, any further evaporation has nowhere to put the salt except the floor of the pan, so the brine is walked on to the crystallisers before that happens.

The colour is not in the salt. It stays in the mother liquor and is drained away with the bittern.

Pan 5 from 300 metres: one concentrating brine pan, the water dense and opaque and streaked in long wind lanes, hard geometric banks on every side. — Pan 5 at saturation, from 300 m printed at 25.7 °Bé

Crystallisers 6a to 6f

25.7 → 27.0 °Bé

Six pans, 20 cm of brine, floors rolled flat and hard. Salt begins to fall the day they are filled and the pan whitens from the edges in. Between 25.7 and 27 the water gives up a little over a quarter of its salt; everything above 27 costs more in gypsum and magnesium contamination than it returns.

On a still morning the crystals meet at the surface first and hold there as a skin. That skin is skimmed by hand before anyone walks in with a rake, because a rake in the pan sinks it.

Crystallisers 6a—6f, the floor at the reading you are standing in 25.70 °Bé · σ 0.00 · 0 crystals down of 460 seeds

The floor above is drawn from the reading you are standing in, not from a timeline: nothing falls below 25.7 °Bé, the count of crystals down rises as the square of the supersaturation, and each one grows by the excess it has seen since it fell. Scroll back up the road and the pan clears, which is what a pan does when rain dilutes it.

Crystallisers 6a to 6f from 300 metres: six small square pans in two rows of three, salt crust whitening each one from its edges inward. — Crystallisers 6a to 6f, from 300 m printed at 27.0 °Bé

What comes off the floor

Raked into ridges, lifted the following morning when it has drained, carried to the mound and left under cover for a season before it is screened. Four grades leave the works, and one liquid.

Grade	Taken at	Pan	Crystal	Last season	Price
Fleur de sel	26.4 °Bé, surface	6c and 6d	plates, 0.4—1.2 mm	1.8 t	£11 / 125 g
Flake	27.0 °Bé, skin	6a to 6f	hollow pyramids	22 t	£9 / 500 g
Coarse	27.0 °Bé, bed	6a to 6f	cubes, 1—3 mm	247 t	£6 / kg
Washed fine	milled from coarse	mound, screened	under 0.5 mm	41 t	£5 / kg
Bittern	29.5 °Bé, drained	6, at sweep	liquor, not a solid	8,900 L	£5 / 250 ml

Fleur de sel: thin flat crystal plates lying loose on a wet surface, each a few millimetres across. — Fleur de sel, skimmed at 26.4 printed in the salt pan, 27.0 °Bé

Flake salt: hollow pyramid crystals heaped together, the largest about five millimetres on a side. — Flake, off the skin printed in the salt pan, 27.0 °Bé

Coarse pan salt: a close heap of hard cubic crystals between one and three millimetres. — Coarse, raked off the bed printed in the salt pan, 27.0 °Bé

Washed fine salt in a glass jar, milled small enough to pour. — Washed fine, milled and screened printed in the salt pan, 27.0 °Bé

A tonne of salt is about 39 tonnes of seawater and a hundred dry days. Nothing is heated and nothing is added. What each grade is for.

A drained crystalliser from 300 metres after raking, the salt lying in long parallel ridges across the floor with wet pan showing between them. — A raked crystalliser, from 300 m printed at 27.0 °Bé

The bittern is what is left over

29.5 °Bé

After the rake, the liquor still standing in the pan is magnesium and potassium salts and the last of the pigment. It is bitter, which is the whole of its name, and it is drawn off into a tank rather than back into the creek.

Tofu makers buy most of it as a coagulant. The rest goes on the marsh hay fields. It is the only thing that leaves this works that we did not set out to make.

A drained crystalliser from 300 metres holding a shallow film of leftover liquor in its low corner, a drain channel running to a squat storage tank on the bank. — The bittern corner and the tank, from 300 m printed at 29.5 °Bé

Then the pans are swept and re-flooded

In October the floors are scraped, the scale is barrowed out, the walls are re-puddled with clay, and the sluice is opened on the first big tide. The reading at the gate goes back to 3.5 and the works spends the winter as a shallow lake with nothing in it but water.

Filling starts in late April. First rake is usually the second week of July. Last is whenever the first September rain is heavy enough to put a crystalliser back down to 24, which it always eventually is.

The works out of season from 300 metres: pans scraped down to bare rolled clay, banks freshly re-puddled, water beginning to stand in shallow sheets across two of them. — Swept, and re-flooding, from 300 m printed at 3.5 °Bé

Season	Dates	Note
Flooding	late April	reservoir first, then 1 and 2
First rake	second week of July	6a and 6b only
Pan walks	Thursdays, 14:00, May to September	twelve people, £8, flat ground, no shade
Sweep	October	works closed to visitors

Order salt

Wholesale from 25 kg, retail at the gate, pan walks on Thursdays — prices, carriage and the number. We do not ship the bittern outside the country; it is a liquid and it is heavy.