Examples of conservation
Iron, for example, requires a more complex treatment, with careful sandblasting using microscopically small glass pellets. This enables the layer of rust to be gently knocked off until the original surface of the artefact emerges. The iron is then heated in a 800°C oven in a nitrogen atmosphere in order to remove various impurities, after which the artefact is impregnated with wax under a vacuum.
|Iron for heating, packed in metal wire|
Artefacts of silver and bronze are normally cleaned under the microscope. Layer by layer, the corrosion is carefully removed with a scalpel until arriving as close as possible to the original surface. Impregnation with substances that prevent decomposition and lacquering are the subsequent treatment.
Recent artefacts, where decomposition is slight, can often be treated by electrolysis or cleaned in a chemical bath.
Large quantities of ceramics are found at archaeological excavations, and everything is washed and numbered. The most interesting and complete clay vessels are cleaned and glued together - work that calls for a high degree of accuracy and patience.
A clay vessel is put back together
Artefacts of an organic composition, e.g. wood or leather, have often lost a large amount of the inner material, which makes the item fragile. Waterlogged wood can be as soft as butter, as the internal cells have degraded and now mainly consist of water. In such cases, the water must be replaced by a synthetic wax that can hold the wood together and preserve its shape. The wood is subsequently freeze-dried.
Archaeological textiles are often very badly preserved. Sometimes, small pieces of fabric are found in connection with, for example, bronze jewellery. The textile has been preserved due to the toxic effect of the bronze, which has managed to keep all micro-organisms away. Often, the textile is carefully cleaned in water, and possibly impregnated and/or freeze-dried.
More recent textiles can perhaps stand being washed or cleaned - this is investigated before each treatment. Certain items of clothing may need support. For this, silk, flax, wool of pieces of cotton are dyed before been sewn onto the reverse of the artefact.
Many artefacts only need washing, which takes place in demineralised water with, for example, a soft brush. Often, the washing is done under a microscope, as it is then much easier to follow the work.
Before beginning a conservation assignment, the artefact is carefully examined. On each occasion, an assessment must be made as to which method of conservation is best-suited. An assessment must always be made as to what the artefact can tolerate, as well as what information can be derived from the object, and what eventually may be lost. Before any conservation is carried out, it will always be preceded by some form or other of identification of material and analysis.