page_title: Conservation and restoration of metals
section_title: Metals and the agents of deterioration
hierarchical_section_title: Conservation and restoration of metals / Metals and the agents of deterioration
caption_attribution_description: English: Treasure Number: 2011 T212 Colchester District, Essex Date of Discovery: 28/3/11 Circumstances of discovery: whilst metal detecting Period: 15th-16th century Description: Half of a post-medieval silver bell. Hemispherical in shape with a soldered loop at the apex, now broken. There is a single band indented around the rim and part of this has now sheared off. The body of the bell is dented and slightly misshapen. Dimensions: Height: 14.33mm Diameter: 14.80mm Weight: 0.8g Discussion:A similar example can be found from the Tendring area, Essex (PAS ref: ESS-481856, 2008 T576). Whereas similar bells were sewn onto clothing as fashionable accessories in the late medieval period, especially in the 15th Century, bells of this kind were, in the 16th Century, used for jesses on hawks and falcons; collars for dogs and cats; as well as being an element in horse furniture. Consequently, in terms of age and as the object contains a minimum of 10% precious metal it qualifies as Treasure under the stipulations of the Treasure Act 1996. Report by: Janina Parol, Assistant Treasure Registrar, British Museum
context_page_description: Conservation and restoration of metals is the activity devoted to the protection and preservation of historical and archaeological objects made partly or entirely of metal. In it are included all activities aimed at preventing or slowing deterioration of items, as well as improving accessibility and readability of the objects of cultural heritage. Despite the fact that metals are generally considered as relatively permanent and stable materials, in contact with the environment they deteriorate gradually, some faster and some much slower. This applies especially to archaeological finds.
context_section_description: An essential cause of deterioration is corrosion of metal objects or object deterioration by interaction with the environment. As the most influential factors of deterioration of historical objects should be pointed out as the relative humidity and air pollution while in archaeological objects a crucial role has composition, depth, humidity and amount of gasses in the soil. In cases of marine or fresh water finds the most important factors of decay are the amount and composition of soluble salts, water depth, amount of dissolved gases, the direction of water currents and the role of both microscopic and macroscopic living organisms.
  Deterioration of materials associated with metals
  Associated materials deteriorate depending on the origin whether they are organic or inorganic materials. Organic materials usually fail in a relatively short period of time, primarily due to biodegradation. With inorganic materials are these processes considerably longer and more complex. Amount of gases, humidity, depth and composition of soil are very important. In case of salty and sweet water finds essential are amount of gases dissolved in water, depth of water, direction of currents, and microscopic and macroscopic living organisms.
caption: Post Medieval bell, height: 14.33mm diameter: 14.80mm weight: 0.8g. Example of physical damage to metal objects.
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