Hodnocení materiálů používaných při readjustaci a ukládání daguerrotypií pomocí modifikovaného Oddyho testu

Unsuitable storage conditions and use of materials which may be a source of pollutants in indoor environments are major threats to the long-term preservation of historic metal objects. Materials proposed for use in protecting and storage of museum or archive collections need to be sufficiently verified in terms of safety for the protected objects before these materials can be safely recommended. One of the basic techniques used for the purpose of testing of new materials (and verifying of those that are already in use) is the Oddy test whose advantages lies in its simple requirements for the experimental equipment and a possibility to modify this method for a particular use. In this work, a variant of the Oddy test was applied with a modification for a specific case – evaluation of materials used for recasing of daguerreotypes. Besides the commonly used visual assessment, electrochemical reduction of corrosion products on the exposed samples was used to compare the Oddy test results. The results indicate that the influence of the test materials is minor compared to the influence of the state of the daguerreotypes surface. This conclusion is consistent with expectations about safety of the tested materials that are used in conservation practice for the protection of archival and historical photographic collections.