Salt is bad, Liminality, and the Harbour at Alexandria

I seem to be on a harbour kick this week, but they keep cropping up in my news feeds so they are what I’ve been thinking about. Or as Levi-Strauss would have said, they’re “good to think with.” Because harbours are interesting places. It’s where the water meets the land, a threshold where ships of war and trade dock, where people from different places interact. One of my professors, Dr. Christopher Monroe, a Senior Lecturer at Cornell University, has recently been spending a lot of time thinking about the liminality of harbors and how that liminality can be approached using nautical/maritime/underwater archaeology. His enthusiasm is infectious, and I too have found myself seeing liminality everywhere.

There was a lot of news today on a subject directly related to this: the lifting of a 9-ton red granite slab from the its resting place on the seabed in the harbour at Alexandria. This particular massive block of stone is believed to have come from a temple built by Cleopatra VII (that would be the Cleopatra, the one who ousted her brother, fooled around with Caesar, and then backed the wrong horse with Marc Antony). Archaeological work has been going on in the harbour since 1994, but nothing has been removed from the water since 2002. This was for good reason: the Egyptian archaeological authorities simply didn’t have the resources to deal with the conservation of artifacts and architecture from an underwater excavation.

The BBC reported that it was because the removal might damage them, which is only sort of true. The actual process of removal, like any excavation, is unlikely to damage the items if done with care. It’s really what happens afterwards thats the problem. The Associated Press article correctly reports that the salt in the seawater is the cause for concern, but in an impressive misunderstanding of science, they claim that when the object is in the water the salt acts as a preservative. This really isn’t true. Salt actually has very little effect on most types of material while they are submerged in seawater, except for the indirect effect it has on the how much oxygen there is present in said seawater. An ancient ship sunk in freshwater can be just as well-preserved as one in salt water. But, likewise, the salt doesn’t do any harm.

Think about it: when you dissolve a spoonful of salt in a glass of water it “dissolves,” and vanishes. What’s really happening is that “salt”, i.e. sodium chloride, is what in chemistry is also called a “salt,” which is an ionic compound resulting from a neutralization reaction of acids and bases. In the case of Sodium Chloride (NaCl), or table salt, one atom of sodium, with a single positive charge (Na+), is neutralized by a single atom of chlorine, with a single negative charge (Cl-). When in solution (i.e. dissolved in water), the sodium and chlorine ions interact with the water (H2O) which actually exists in a partially ionized state itself (H+ and OH-). Basically, all the ions are floating around together, neutralized, stable, and happy. But when the water is removed, say for example by evaporation, the sodium and chlorine ions are left on their own, and in a panicked effort to stabilize themselves they link up, and they happen to link up in an orderly fashion, which is what produces crystals. This orderly crystalline structure that the ions aline themselves in is sort of like an open-lattice, so it also takes up way more room in crystalline form than it did when it was just a bunch of little individual ions.

This whole process isn’t so much of a problem when it happens on the surface of something. When you go to the beach and go swimming and then fall asleep in the sun, you just wake up with a thin layer of salt crystals all over your body, which you can just brush off with a towel. But when an object is porous and all the water evaporates from inside it, the salt will crystallize wherever it happens to be and that includes inside the porous object. And in reality, just about everything is porous if you leave it sitting in water for several hundred years. Even granite. And when those ions form up into their surprisingly strong lattice crystalline structure, where they take up way more room than they used to, the resultant salt crystals will push on and possibly even break apart the material that they’re forming inside. Even granite.

So what this means is that if you were to pull an object out of the sea that’s been saturated with saltwater, say a giant slab from the pylon of Cleopatra VII, and then just let it sit in the sun to dry out, little salt crystals would form all over the inside of the stone, and it could quite possibly crumble into a heap of dust. This would be why the Egyptian government didn’t want people pulling things out of the harbour at Alexandria. Fortunately there is a reasonably simple solution to this problem. If you take the object that has been saturated in seawater and soak it for several months in rotating baths of fresh water, the salt can be leached out of the object until it is sufficiently desalinated and safe to allow it to dry. Such will be the fate of this carved granite block, which took three days to drag to safety away from the shipping lanes and close enough to shore for a crane to pull it out of the sea, only to be put back into a giant tank of water.

So, what does this have to do with liminality? The word “liminal” comes from the Latin, limen, meaning “threshold” or “doorway”, and in the early 20th century entered anthropological discourse in Arnold Van Gennep’s seminal work, Les rites de passages. In this work liminality is presented as the second of the three stages a person passes through in a rite of passage: Preliminary (separation), Liminal (transition), and Postliminary (reintegration). The liminal phase is characterized by ambiguity and paradox, during which the participant exists simultaneously to both the preliminary and postliminary states and to neither.

This is a great metaphor to consider a harbour with. A harbour is the physical embodiment of a doorway or threshold for a city or civilization. The ships and people who pass through it belong both to their home ports and to those that they visit, while also having no home at all. The harbour is of the sea and of the land, but is also its own thing, and the harbour at Alexandria is no exception.

Berth for the world’s great fleets, former site of mighty palaces and temples, crossroads of the Mediterranean, center of trade, war, and knowledge, the harbour has seen history pass, and it now holds in its depths the remains of that history, the detritus of history trapped in its own liminal state, having both passed out of time and memory, but also preserved, not truly allowed to fade. And this one block (9 tons of carved red granite), of this temple (to the goddess Isis), built by this queen (Cleopatra, perhaps history’s most famous), has finally escaped its liminal state in the murky depths of the harbour…

…only to enter another liminal state, stuck in a tank of fresh water in a conservation lab, thanks to being submerged in salt water for 2000 years. Thankfully, this one should be a lot briefer.

BBC News – Egypt lifts huge ‘Cleopatra temple’ block from sea
Monument lifted from Cleopatra’s underwater city