Variation in Colourants of the Dyes by Gamma-ray Irradiation

Abstract

The emergency conservation of historical objects is necessary because several instances in which paintings and records were flooded owing to unusual weather conditions have recently been reported. Early action is especially important in preventing biodeterioration in case of flood damage. In this study, the feasibility of using gamma rays as a biological control method was assessed. Material stability was evaluated by applying different irradiation doses to natural dyes used in historical paintings and costumes. Sappan wood, gardenia fruit, and indigo were selected and prepared as natural dye samples using standard colorant materials. The fading behavior of the samples was analyzed by measuring their CIE L*a*b* color space values, and UV-Vis spectroscopy and liquid chromatography tandem mass spectrometry (LC-MS) were used to obtain their spectra. We confirmed that the dyes began to decompose upon exposure to gamma rays at a dose of 10 kGy. Irradiation at a dose of 50 kGy led to the complete decomposition of the chromophoric groups because the dye components could not be detected by LC-MS. Therefore, studying the influence of low-dose gamma-ray irradiation is necessary to preserve dye colorants. The data obtained in this study can be used as a foundation for further research on the influence of gamma rays on historical objects.