Desalination of Archaeological Composite Objects Consisting of Wrought Iron and Wood/Bone. With Focus on the Iron Component.

Abstract

The difficulty of choosing a suitable treatment for freshly excavated composite objects from archaeological sites is a well known problem within the field of conservation. The array of different materials, their shape and condition, degree of deterioration and their individual demand on correct treatment along with their effect on each other through time is a complicated combination of factors. In order to preserve iron, it is important to eliminate as much Cl- as possible after excavation. This is usually done through treatments in alkaline solutions. However, the high pH of these solutions (pH 12 – 13) is extremely destructive to the organic components in composite objects containing wood and bone. The Western Australian Museum has been using mineral oil as a seal during the desalination process of iron in alkaline solutions. They report that it is possible to prevent the absorption of carbon dioxide as to avoid the pH dropping in the solution for up to 6 weeks. The aim of this thesis is to investigate the suitability of the use of mineral oil as a sealing agent to exclude the ingress of oxygen during the desalination process on composite iron/organic objects. The focus of this project lies on the effectiveness of the treatment of the iron component in composite objects. The results of my work indicate that distilled water with mineral oil as a sealing agent to exclude oxygen for the treatment of composite objects does not work sufficiently. This conclusion is based on the amount of sediment and the iron in the solutions that showed a high level of corrosion on the objects.