Radiosterilization of historical documents: the potential effects of gamma irradiation on paper and printing inks

Abstract

The controlled exposition to gamma radiation is a physical process which can be used for the preservation and recovery of historical documents. Depending on the intrinsic characteristics of the material to be treated, it is necessary to research and stablish, from time to time, the optimum dose rate and total dose, the conditions to eliminate or reduce the biological threat, the equipment and its logistics, the economic aspects and any other impact caused by radiation on the material to be treated. The references indicate that through research it is possible to consolidate the knowledge about gamma radiation emitted from 60Co in order to completely remove or at least greatly reduce infestation by insects or biodeterioration microorganisms. On this work we have used a MDS Nordion self-contained 60Co research irradiator, model Gamacell Excel 220, at Postgraduate Institute of Engineering and Research Alberto Luiz Coimbra, in Rio de Janeiro Federal University. The analysis of the samples submitted to controlled thermal dry aging and to gamma radiation made possible to verify the differences between treated and untreated samples. The results of the chromatic measures indicate that, with the optimum total dose, the gamma radiation treatment does not significantly alter the properties of paper or printing inks. This way, it is possible to conclude that even though the gamma irradiation of historical documents is a complex procedure which demands a detailed study in order to assure its safe application, it is environmentally safer than the use of chemical pesticides