Dosimetry of paintings: determination of the degree of chemical change in museum exposed test paintings (azurite tempera) by thermal and spectroscopic analysis

This paper describes the effects of accelerated artificial and natural agei ng on samples of azurite paint tempera prepared according to traditional ea rly Italian recipes. The pigment used was basic copper carbonate in the for m known as azurite and this was mixed using whole egg tempera medium. Artif icial and natural ageing of the dosimeters was performed using controlled a geing chambers and selected sites of varying environmental conditions. The effects of ageing were quantified using a number of analytical techniques, which include the following: thermal analysis (DSC and TGA), scanning elect ron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The data w ere then compared with those obtained from samples which were naturally age d by exposure in selected European art galleries and historic castles for a period of 9 months. It was found that the changes observed on artificial l ight ageing alone were minimal. Mass spectrometry (DTMS) showed that sample s had already undergone oxidation during the curing stage of 3 months [O.F. van den Brink, G.B. Eijkel, J.J. Boon, Thermochim. Acta 360 (2) (2000), th is proceedings]. There were, however, measurable differences in the samples that had been subjected to thermal and pollutant ageing, and this was used to rank the sites. (C) 2000 Elsevier Science B.V. All rights reserved.