When an archaeological excavation has finished, measures need to be put in place to make sure that everything that came out of the ground is documented and safely stored. We call everything that comes out of the ground ‘the archive’. This can include finds that are obviously important and precious such as old coins, glass bowls and swords as well as the less obvious like building materials, animal bones and broken bits of pot. It can also include information about the excavation such as drawings and descriptions of the different soil layers – we call this the paper archive. Everything that comes out of the ground in an archaeological excavation can tell us something about how people lived in the past and so it is very important that it is all looked after.
Looking after the archive means it is absolutely important to make sure that it is kept safe. This can mean safe from being stolen, but more importantly it means safe from deterioration. This is particularly the case with the finds archive. When things lay in the ground they become used to a particular chemical climate. When they are taken out of the ground this climate changes and small chemical reactions can take place on the surface of the finds which can lead to corrosion, discolouration and decay.
To stop this from happening we send finds to conservators and local museums who try to replicate the chemical climate that the finds were in, or cover the finds with other chemicals that stop harmful reactions happening on the surface. Museums also play an important role in making sure that the finds archives are accessible to the public. While we wait to send finds to conservators or museums we make sure the finds are as safe as possible by storing them in non-corrosive materials such as polythene and acid-free cardboard.
When we send finds to museums we have to make sure that everything is labelled so that the museum, and people who might be interested in the site in the future, can tell exactly where the finds came from and exactly what they are. In many cases we also label the finds with an “accession number” given by the museum so if the archive gets lost and is found again they will know who it belongs to and which site it came from.
We also make sure the paper archive is ‘safe’. Although paper won’t deteriorate as fast as some archaeological finds, it is still at risk from things like damp, falling apart, getting mouldy and discoloured. As a result we make sure that all paper archives are also stored in acid-free cardboard and materials such as staples and sticky tape are removed as these can damage the paper over a long period of time. Acid-free cardboard also limits reactions between some inks used to write information down about the site and chemicals found in the air. These can cause the ink to fade over time making it difficult to read. We also try to make digital and/or paper copies of the paper archive so that if one version is lost or ruined there will be another that is safe. Like the finds archive, the paper archive is sent off to the local museum where it is looked after, labelled and made accessible to the public.