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Dating and preservation

Most materials degrade over time, but their lifespan can be extended through preservation. There are many different ways to determine the age of objects.

Methods to determine age

These are some of the methods for dating objects or materials.

C14, measuring carbon isotope

All organic matter – anything that has ever been alive – can be dated using the carbon-14 method. The carbon isotope C14 is found in all living organisms, but the proportion slowly decreases after death. By measuring how much C14 isotope remains in a wood sample or animal bone, it is possible to determine when the tree or animal died.

Dendrochronology, analysing tree rings

Annual tree rings in a tree increase with the age of the tree. They can vary in thickness depending on whether the climate was hot or cold. By counting the tree rings and comparing the patterns of the wood with other samples whose age is established, you can determine what kind of wood it is, where the tree grew and when it was cut down.

Stratigraphy, layer by layer

When people live in the same place for a long time, layers are formed containing soil and things that have been dropped, broken or thrown away. Layer by layer, the archaeologist can look back in time.

Typology, comparing finds with each other

Another way to determine the age of finds is to compare them with other similar finds discovered in the past whose the age is established. This is called typology. On a wreck, you can do things like study how it was built, what shape it had, what the masts and sails looked like and what kind of figurehead it had. These facts are then compared with other similar wreck finds.

What’s salvaged must be preserved

In cold and dark waters deep down in the Baltic Sea, objects can be preserved for an extensive time. But when objects that have been in water for a long time are brought to the surface, they begin to degrade quite quickly.

Different materials last different lengths of time and behave differently. For example, wood from a wreck that has been in water for a long time becomes very brittle and can fall apart when it dries out. Oxygen in the air triggers chemical processes in other organic materials too. Biological organisms such as fungi and bacteria can also break down objects and remains.

Expensive and rather tricky

So most of what is salvaged from the water needs to be preserved, meaning treated in different ways so that it lasts a long time and is not destroyed.

Conservation is often expensive and time-consuming. And when the conservation is complete, the objects must be stored in rooms or containers with specially regulated temperature and humidity so that they are not destroyed. In the end, the best way to preserve old shipwreck objects is to leave them on the seabed where they thrive best – where the water is dark, cold and lacks oxygen.

Page last updated: 2021-06-24