Unearthed: From Excavation to Display
An introduction to the role and work of a conservator
The Collection: Art & Archaeology in Lincolnshire ( http://www.thecollection.lincoln.museum/ ), provides an unprecedented level of access to the rich, diverse, and (in some cases) internationally significant artifacts within Lincolnshire County Council’s archaeology collection. This access is achieved through the work of many dedicated staff, including specialist conservators. The Museums and Collections Care team, and specifically the conservators within that team, has a national reputation for the quality of its work.
The conservation of archaeological material is a complex process which demands a high degree of professional judgement of its practitioners. Excavated archaeological material is likely to be in a significantly deteriorated state and, ironically, this is usually exacerbated by recovery from burial, with its accompanying sudden environmental changes.
Approach to conservation
Differing site conditions will almost invariably be in very different states of preservation. For example, leather from a waterlogged (and usually significantly oxygen depleted or even anoxic) excavation is likely to be well preserved by that environment, although extremely sensitive to changes brought about by its removal from it. On the other hand, leather from what might be loosely referred to as a typical urban burial context (well drained and oxygen rich) is unlikely to survive at all, sometimes being present as nothing more than a stain in the soil. Couple this with the wide range of materials likely to have been deposited in antiquity, and the further complicating effects of occasionally localised burial environments, and the task facing the archaeological conservator perhaps begins to become apparent. Necessarily, then, it is important to adopt a well-structured strategic approach to dealing with the conservation of excavated archaeological material, regardless of the size of the assemblage.
Lincoln’s conservation team bases its approach firmly upon the regulatory guidance contained in English Heritage’s archaeological project management documentation (known “in the trade” as MAP – The Management of Archaeological Projects). This management framework is accepted throughout the archaeology profession as a best-practice benchmark, and it succeeds in describing archaeological project work as a staged process between planning and publication.
The wide range of materials that any excavation may potentially yield, merit a bespoke approach in terms of their post-excavation conservation treatment. Organic materials such as bone or wood demand quite different treatments to those applied to inorganics such as metal or glass. However, the factor which unites the conservation approach as a generic function, is the fact that anything recovered from an excavation is likely to be in a fragile and deteriorated condition, and very susceptible to post-excavation decay as a result of being removed from the ground.
Different sites will preserve objects differently. Where there is no oxygen, micro-organisms that break down matter such as wood, leather or skin cannot survive and objects can remain almost as good as new for thousands of years. Any decay that does take place is replaced by the water and become ‘saturated’. As soon as it is removed the object dries out and shrivels. Also, the process of decay begins again as soon as the objects are exposed to the air. It is the same with iron objects. Rust requires oxygen to occur; no oxygen, no rust, but as soon as an iron object is uneartherd and exposed to the air then decay will begin rapidly. It is the job of the conservator to stop this.
Whatever the individual treatment the conservator applies to such materials, the desired outcome of the treatment is always to stabilise the condition of the object as far as possible, and thus minimise further deterioration. This task is fundamental to the work of the conservator, and time is always of the essence. Without such action an artifact may rapidly deteriorate to a point which is irrecoverable.
Metals can develop ‘active corrosion sites’ which, if unchecked, can spread resulting in delamination and eventually reducing the object to nothing more than a powdery crystalline mass. Organic materials from waterlogged environments, which survive as a result of their “saturated” structure, will shrink and warp beyond recognition if the water is not removed in a controlled way by a technique such as freeze-drying. Whatever the treatment applied, it is incumbent on the conservator to apply critical judgement, to assess condition accurately, and to tailor treatment needs accordingly.
Equally important in the stabilisation of artifacts is the manner in which they are packaged and encapsulated, once any active deterioration has been brought under control. Not only should such packaging ensure robust physical protection without hampering access, it also needs to provide any special ‘microenvironment’ that a particular material might need, such as a dry atmosphere for metals.
Inadequate packaging, which does not respect the object’s potential future handling and use will (at best) not afford the sort of long-term integrity which the object merits, and (at worst) is likely to undo the stabilisation treatment applied to it following excavation.
Having satisfactorily stabilised an assemblage the conservator is then called upon to undertake “forensic” style investigations to assist interpretations made by artifact researchers, prior to the materials transfer to a long-term custodian such as a museum.
Wherever possible this phase of work will seek to use non-destructive techniques such as optical microscopy or direct x-radiography. The latter is extremely useful in relation to archaeological metalwork, establishing a range of information about details often completely obscured by corrosion. Valuable data relating to condition, decoration, and technology can be elicited in this way. More specialist techniques, such as x-ray fluorescence spectrometry, can clarify (for example) the composition of platings, inlays, or other forms of decoration on objects. Where non-destructive examination is unable to provide answers to legitimate archive queries then it may be necessary for the conservator to adopt a more interventive approach, such as the physical removal of small ‘investigative windows’ of corrosion from a metal object to reveal a specific feature more clearly.
There are many other examples of this type of forensic style work which a conservator might need to undertake in the course of their duty. However, it is fair to say that any such activity must be the result of close cooperation between conservators and researchers, and must set out to make an assemblage more understandable for scholarly or other advocacy purposes.
At this point the resulting stable and intelligible assemblage is fit for transfer to its long-term home, normally a local repository such as a museum store. How, then, might a conservator be involved with the material ‘post-transfer’? Perhaps the most fundamental contribution made is concerned with the long term care of such material, as it complements and swells the local archaeology collection.
Curatorial staff who are responsible for museum collections play a large part in this process, although it is the conservator who must specify the environmental parameters (temperature, relative humidity, light, etc) against which those responsibilities are discharged.
However, it is not the role of the museum just to preserve these collections, essential as this function is. Under the banner of collection “stewardship” museums are also charged with making such materials accessible to as wide an audience as possible. This is undertaken in a variety of ways:
- Displays - many of which involve the conservator in significant levels of aesthetic enhancement work, such as the removal of obscuring accretion from metals, or perhaps the restoration of fragmented pottery,
- Various outreach mechanisms - such as loans boxes; and,
- Digital / online access.
Whichever method or blend of methods is adopted by the museum, one thing remains a constant - any activity of this nature is likely to have an impact in terms of wear and tear on the artifacts concerned. The more directly accessible objects are made, the more ‘at-risk’ they are likely to be. This long-standing dilemma is resolved by good museum management, balancing the desire to make things accessible for the public with the responsibility to ensure the collection’s long term survival.
Although sometimes the least ‘visible’ of the range of specialists likely to be encountered in the museum environment, the conservator has perhaps one of the most crucial roles in ensuring the preservation of our archaeological ‘treasures’.