In our first expedition to Pompeii (May 2010) and thanks to the invitation made by Antero Tammisto from EPUH and Dr. Ulla Knuutinen from Helsinki Metropolia University at that time, we were able to perform in situ measurements in the House of Marcus Lucretius (Regio IX, Insula 3, Houses 5 and 24). In our first year in Pompeii we transported to the site one portable Raman spectrometer together with a motorized tripod and a portable infrared spectrometer (DRIFT mode). With this instrumentation we were able to perform in situ analyses on walls and wall painting remains. Dr. Ulla Knuutinen performed also elemental in situ measurements using her hand-held energy dispersive X-ray fluorescence (ED-XRF) spectrometer. Those analyses were combined with the ones performed by the members of APUV.
This year we focused our attention in the analysis of the blackened red areas (hematite as original pigment) of the fauces (entrance area) of Marcus Lucretius House. With these analyses we were able to confirm our first observations performed on some micro-samples extracted from the same areas analyzed in situ regarding the transformation of the original red pigment hematite (Fe2O3) into a black magnetite (Fe3O4). In the fauces we also performed additional analyses on the plaster and blue pigment remains (Pompeian blue).
Other areas in where in situ analyses were also performed were the atrium of the house (presence of green pigments made up of a mixture of Pompeian blue and yellow ochre) and the triclinium (dining room). In this last case, we focused our attention on the identification of possible traces of cinnabar included as red colour in the wall painting remains from this important room of the house. Finally, in this house we were also able to characterize the plasters and possible pigment remains (almost invisible to the naked eye) present in the summer triclinium from the house.
Apart from the characterization of the plasters and pigments from the House of Marcus Lucretius, this year some preliminary analyses were also performed in efflorescences and walls from the House of Obonius (see more details in the year 2011).
Apart from the on site works in the archaeological site of Pompeii we also transported our portable instruments to the Naples National Archaeological Museum (MANN). There, we were able to perform non-invasive analyses in the storehouse of the museum in order to characterize the composition of the pigments and plasters used in three painting panels extracted from the original mural paintings of the House of Marcus Lucretius in the first excavations executed in this house more than 160 years ago. More specifically, the analyses were conducted on the panel 9103 (Little boys playing) removed from the west wall of Room 25 (summer triclinium) and on two panels removed from Room 16 (triclinium); the panel 9208 (Cupids and Psychai with a dancing Psyche) from the west wall and the panel 9206 (Cupids and Psychai preparing a lyrical presentation) from the south wall.
After finished our field analysis in the archaeological field of Pompeii and MANN, Maite Maguregui travelled to Vienna in order to perform a predoctoral internship during 1 month in the Natural Sciences and Technology in the Arts Institute (Academy of Fine Arts, Vienna). During this period of time, Maite was able to conduct different accelerated weathering experiments on some wall painting fragments that were recovered from the excavations of Marcus Lucretius, showing red hematite pigment layers totally well preserved and without a sign of alteration. These fragments were subjected to different cycles of exposures against SO2 gas, in order to simulate the impact of this acid gas (coming from the modern atmosphere but also from the natural volcanic emissions) deposited following a wet process and its key role in the transformation process of red hematite into black magnetite. Thanks to these experiments we were able to confirm the reactivity proposed and modeled using thermodynamic tools at the sight of the experimental evidences (presence of magnetite and gypsum in the blackened red areas). The results extracted after measuring real samples and those obtained from the accelerated weathering tests give rise to two scientific publications in Analytical Chemistry and Analytical Methods journals (see Scientific Contributions section).