Using atmospheric pressure plasma as a tool in the cleaning of icon paintings

The removal of aged and unwanted layers from the surface of a work of art is one of the most significant operations in the conservation process, but it is also complex, risky and hard to control. The plasma cleaning procedure has been tested successfully on different materials representative in the field of cultural heritage and has proven its many advantages compared to mechanical and chemical cleaning techniques. Despite the success of atmospheric pressure plasma treatment in the cleaning of easel paintings (i.e. the removal of thin films of varnishes, resins, re-paintings or deposits) it is still a new research area. This paper presents the use of atmospheric pressure plasma (APP) for the removal of aged varnish, wax and soot from the pictorial layer of an icon painting. The case study is conducted on a 19 th century wooden alms box with a painting of Saint John the Baptist and compares the influence of two different concentrations of the used gas mixture. Better cleaning result is obtained using APP Ar/O 2 0.2%. The successful removal of the aged oil-resin varnish, wax and soot deposits, is assured without any mechanical and chemical modification of the underlying pictorial layer. The surface action of the plasma treatment is an important advantage compared to the use of aggressive solvents, mechanical shock, or local heating which is typical of traditional cleaning procedures. Furthermore, the non-contact treatment with plasma does not require preliminary consolidation of the treated surface, and avoids additional drawbacks. This method is a rare opportunity, especially in cases when the surface is protected by an organic material and could be neither safely, nor acceptably cleaned by the existing conventional techniques. Therefore, the use of plasma is proposed for the cleaning of icons as an alternative or complementary treatment to the existing techniques.