Archaeological materials in Australia are generally uncovered from early colonial occupation sites, marine environments, burial sites or ruins. They can be made from a wide range of inorganic and organic materials including metals, stone, ceramics, bone and skin, wood and plant fibres.
In addition, Australia has significant collections of ancient materials from the Stone or Bronze Ages, as well as Greek and Egyptian antiquities in both public and private collections.
Pewter spoons recovered from the VOC Avondster 1659 wreck site located in Galle Harbour, Sri Lanka. Photo: Jon Carpenter, courtesy of Western Australian Museum.
Types of deterioration
Both marine and terrestrial archaeological materials form chemical reactions with the water and sediments of the environments in which they have been immersed over long periods of time. Removing these objects suddenly from their environment and exposing them to air can create chemical and physical reactions.
Water moves into materials and carries agents dissolved in it and is a deterioration factor for all environments. Drying water on objects leaves salt behind and affects all materials, particularly causing corrosion in metals and physical damage in non-metals and organic materials. Build up of salt inside ceramics and other porous materials may slowly damage their structure over time if not treated.
Biological growth such as bacteria, fungi or mould, and in plant life that may be attached to archaeological materials increases the physical decay of both organic and inorganic materials.
Long-term neglect, mishandling and inappropriate storage present the most common threats to archaeological materials, causing breakage and other physical damage. The moment these materials are excavated, they are at risk of deterioration and require both archaeological and conservation knowledge in order to be preserved for study and display.
Many archaeological materials may be covered in sediment or corrosion at the time of excavation, making it difficult to ascertain their components and structure and to assess their condition.
Direct handling should be kept to a minimum to avoid further damage. Archival quality containers and packaging materials customised to the object should be used when transporting from the excavation site.
Corroded metal objects should be kept in a stable, airtight storage environment with minimum changes to humidity and temperature. Attempts to clean corrosion, remove dirt and sediment, or other accretions may do more harm than good. Not only does this increase risk of damaging the object beneath but also removes important information about the object, its historical use and context that might be used for research or conservation purposes.
The AICCM Objects Special Interest Group is for those interested in the conservation of objects, including archaeological materials. Join this group, contribute to its activities, or speak to a specialist conservator.