The 2005 field season of the EPUH (Expeditio Pompeiana Universitatis Helgiensis) project took place in May and the number of participants was larger than previous campaigns: half of the staff was made up of researchers and students from the University of Helsinki and the other half came from EVTEK (Technical University of Helsinki). The excavation of a large area in the House of Marcus Lucretius (Regio IX, Insula 3) contained several rubbish pits which were dug into untouched volcanic layers. One of these pits was full of extremely well preserved second style wall painting fragments, which were needed for the pigment analysis performed by EVTEK team. By 2007 these fragments, which were assigned to paints of the second and fourth style roman mural paintings, were analyzed by X Ray Fluorescence (XRF) at EVTEK under the supervision of Dr. Ulla Knuutinen, before we met her.
In 2008 Dr. Knuutinen sent us some of those samples (mortars with and without painting layer) so we performed different analytical procedures to identify the composition of the different samples. The samples were analyzed non-destructively by Raman spectroscopy to ascertain the compounds present in the different layers. Moreover the soluble salt test was applied measuring the dissolved concentrations of cations and anions by ionic chromatography. These quantitative results were treated by chemometric tools to find grouping among the different ions.
To our surprise, we detected all of the expected compounds (those referred in the literature as being part of the different layers in Roman mural paintings of the second and fourth styles) together with other non-expected ones but typical of the interaction between modern atmospheres and original materials belonging to cultural heritage (details are give in the next section).
We exchanged this information with Dr. Knuutinen and the purpose of the research was modified to include not only the characterization, but also the diagnosis of the conservation state of the samples and the identification of the possible sources that impacted (or are impacting) the walls and mural paintings of the House of Marcus Lucretius.