Why Treat Objects?

Conservation means to preserve something. Most things brought up from the sea need to be preserved if they have been on the seabed for a long time, otherwise they crumble away. The job of the conservator is to make the object stable again - to preserve it.

Once a ship wrecks, the ship and the objects on board her start to decay. Metal starts rusting and wood gets eaten away by sea worms. Sometimes they will be protected by a layer of sand or mud, and as long as nobody disturbs them, objects will be preserved on the seabed.

As soon as divers stir up the sand, anything preserved underneath it starts decaying all over again. That's why archaeologists try to dig up small areas at a time, so they can limit the damage they do to the wreck site. Once they bring anything to the surface, the object begins to decay immediately from the chemical shock of moving from water into the open air. Often archaeologists try to keep things wet, to limit the damage to the object. Whatever happens, the object needs to be preserved or else it will fall apart.

What is Concretion?

Metal on a wreck starts to corrode as soon as the ship sinks. As it rusts (oxidizes), bits of sand and shell stick to it, and over time this forms a hard shell around the object. Sometimes coral and weeds also stick to it, making it very difficult to identify on the seabed. The shell also protects the object from rusting away any further.

At some point, the Conservator will take off the concretion and try to preserve the object underneath. It can be chipped off with a small hammer, scraped off using a dentist's tools or even peeled off using a vibrotool. Because the object underneath the concretion is often very fragile, conservators need to know exactly what to do and which tool to use. Things like X-Rays help them to know what lies under the concretion, but they need all their skill to do the job properly, without damaging the object.

Electrolysis

Most metal raised from the sea contains salt (sodium chloride) from its stay on the seabed. If the metal was left untreated, the salt would react with the air and the object would crumble away. The conservator needs to take the salts out of the object before it can be shown in a museum.

To do this, conservators use a process called electrolysis. By running an electrical current through the object they can start a slow chemical reaction which draws the salt out from the metal. A negative current (-) is run through the object and a positive current (+) is run through a metal strip in the tank holding the object. The water in the tank conducts electricity, so the current move from the object to the metal strip, taking the salt with it. The whole process can take from a several days to several years. It all depends how big the object is being treated and how much salt is in it.

After the treatment is finished, the object is rinsed, cleaned, dried out and coated with paint or some other protective coat. It is now ready to go on display in an exhibition like this one.