Bruce A. Banks, Sharon K. Rutledge, Maura O’Malley and Scott A. Snyder
Abstract
Soot and other carbonaceous combustion products deposited on ceramic, marble, ivory and metal art objects can be difficult and potentially unsatisfactorily removed by wet chemical means. An atomic oxygen source which operates in air, at atmospheric pressure, on a gas mixture of oxygen and helium, has been developed which produces a pencil-thin beam of single atom oxygen ions and neutral atoms. This device has been successfully demonstrated to fully remove carbon and hydrocarbon products deposited as a result of smoke damage on various substrates. The atomic oxygen beam will not react with already oxidized materials, and the oxidation process quickly stops once the carbon and hydrocarbon contaminants have been removed. The atomic oxygen source can be used in a gaseous spray cleaning manner in which an area of only a few millimeters in diameter is treated at one time.
The source is capable of being hand held or mounted on an x-y translation system to provide uniform cleaning over an extended surface. The source is held within a few millimeters of the surface of the object to be cleaned of organic contaminants while a 3-5 mm diameter beam of atomic and ionic oxygen is directed at the surface of the object. When the atomic and ionic oxygen beam interacts with organic contaminants or coatings, oxidation of only the outermost exposed surface occurs resulting in conversion of the organic surface to gaseous carbon dioxide, carbon monoxide and water vapor.
Results of cleaning opaque black soot deposits on ivory, stone and gesso substrates demonstrated complete removal of all visible soot with the substrate returning to its original appearance. Quantified optical laser reflectance measurements have been used to measure the effectiveness of the atomic oxygen beam cleaning process. The design characteristics, functional performance and photographs of the results of cleaning smoke damaged objects will be presented.