Expanding shot with lead weights in passive desalination

Expanding shot with lead weights in passive desalination

The first priority when objects are removed from the sea is to prevent them from drying out with the consequent crystallisation of the salts within them. It is also very important to keep metal objects and concretions wet because the presence of much higher levels of oxygen they will begin to corrode vigorously – so much so that sufficient heat may be generated to cause them to disintegrate explosively – this is a particular problem with cast iron cannon balls.

Concretions need to be x-rayed so that the nature of the original object can be determined and its significance assessed. With this information decisions can be taken about the conservation path that will be followed.

For many finds conservation will be simply a matter of soaking in water over many months. As the salt diffuses out from the objects the water will become increasingly saline and will have to be changed periodically. The end point of this treatment will be when the water no longer has a higher salt content than the water from a tap. Some very fragile objects and metal objects may need a further period of soaking in distilled water to remove the last traces of salts. This procedure will be all the conservation needed by a high proportion of our finds and following it they can be safely housed in an environmentally controlled store for study and display.

More significant objects need to be professionally conserved. A great deal of care has to be taken over what we select for this process: conservation is expensive and our resources are limited. Once the decision has been made we contract the work to the conservation team at the York Archaeological Trust which is one of the very few conservation laboratories able to deal with the range and size of materials that we recover from the site.

Read more about conserving finds from the wreck.