| Abstract: | SUMMARIES. A Roman wall painting of the first century AD, recently discovered in Rome, has been studied exten¬sively, in situ, by non-destructive X-ray fluorescence (XRF) analysis. The coloured pigments, the medium and the plaster were all examined. The presence of potassium and calcium in all coloured layers demonstrates that the painting technique is of a type very similar to that used in Pompeian wall paintings, and described in the 1950s by Selim Augusti. In this type of wall painting, the pigments were dissolved in a lime/soap/water solution, the function of the soap being to mitigate the negative effects of lime on alkali-sensitive mineral-based, colours.
CONCLUSION. The finding, reported in the previous section, that alkali-sensitive pigments were used in a lime-con¬taining matrix leads us to suppose that a particular type of 'chemistry' was used in order to annul the lime attack on these mineral colours. This, along with our other observations from non-destructive analysis, persuades us that characteristics of this painting correspond to those of the type of Pompeian wall paintings first described analytically by Selim Augusli [1]. Figure 10 is the flow chart proposed by Augusti to represent the steps involved in the preparative and painting processes. In our results we found several fundamental aspects that agree with Augusti's description. First, the presence of calcium and strontium in the coloured layers, in conjunction with the use of pig¬ments that are incompatible with lime, suggests that a neutralizing additive must have been employed. Secondly, the detection of potassium in all points examined is in agreement with the hypothesis that a water/soap solution was employed that comprised a potassium-containing wood ash combined with fat. In the near future we hope to start non-destructive analysis of the organic components, to look for the wax and animal fat found by Augusti. In conclusion, the authors believe that in Latium several wall paintings were made using the same complicated procedure as in Pompeii. A similar preparation was also found in a wall painting at the "Villa di Livia', dating to 20-10 BC, which was recently analysed by XRF [11]. |
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