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The physicochemical investigation of ceramics crafted and managed by ancient humans allows a better understanding of their social, technological, economical, routine and artistic activities. The Brazilian State of Rio Grande do Sul presents the biggest number of registered archaeological sites in the country, and many of them are earthen mounds, locally known as cerritos de indios. This kind of archaeological site is of utmost importance to understand the social development of the biome Pampa – including areas from Brazil, Argentina and Uruguay – and almost nothing is known about the physicochemical composition of the artifacts from the Brazilian portion. In this work we investigated the mineral phases present in archaeological ceramics from the cerrito Pavao I (PSG-20) by means of white light microscopy (petrography), Raman micro-spectroscopy, XRD and XRF spectroscopies, and FTIR-ATR. Different minerals were identified and allowed to propose a firing temperature of ca. 500–650 °C. It was also suggested that the makers used both oxidizing and reducing atmospheres, that more than one clay source was used to prepare the ceramics, and that trace elements are present in different shards. Regarding the multi-analytical technique approach, the results highlight the importance of complementary investigations and underline the role of Raman micro-spectroscopy for these objects.

Vibrational spectroscopy and GC–MS were used to investigate the effect of MnO 2 and α-Fe 2 O 3 on the degradation of methyl linoleate and vegetal and animal fatty. The metal oxides are among the most employed pigments in rock art paintings, whereas the organic compounds were used to mimic organic binders potentially used in such paintings. Both oxides were very effective in the catalytic oxidation of the organic substrates and light had no significant effect, qualitatively or quantitatively, on the final products. In the case of methyl linoleate without metal oxide, the effect of light (visible) was investigated and it was demonstrated that the samples kept in the dark produced relatively less oxidation products, although the main products were the same (hexanal, methyl 9-oxononanoate and methyl octanoate). In the presence of MnO 2 and α-Fe 2 O 3 methyl 9-oxononanoate was the main product, followed by hexanal. The spectral patterns of the oxidation products were different for manganese and iron oxide and GC–MS demonstrated that more compounds are formed in the former than with α-Fe 2 O 3 . Vegetal and animal fatty presented the same behavior that methyl linoleate did. The results here reported indicated that the two pigments considered actively contribute to fat degradation and the presence of inorganic pigments is the main factor to take into account when organic binders degradation in rock art paintings are investigated.

The present work is focused on the role of formaldehyde in indoors Pb corrosion, that is still a controversial issue. Pb coupons were exposed to the atmosphere produced by formaldehyde aqueous solutions (1% and 4% in volume) and corrosion was followed by Raman Microscopy. The compounds formed in both experiments were the same, but were not in agreement with previously reported results in the literature, that identified plumbonacrite, hidrocerussite and Pb oxide. The experiments here reported have clearly shown that formates are produced on Pb surfaces exposed to formaldehyde and that oxidants, such as H2O2, are not necessary. Formaldehyde oxidation also occurs with powdered PbO in a controlled environment. The Raman spectra of the Pb formates are much more complex than the Pb(HCO2)2 spectrum and change when exposed to room conditions, by a slow reaction with CO2, forming Pb carbonates (hidrocerussite and plumbonacrite mostly) and Pb(HCO2)2. Such spectral change may be responsible for the differences in terms of chemical composition of the corrosion layer when the data here reported is compared with the literature. Other factors that must be considered are the storage conditions (particularly relative humidity and CO2 concentration) and time; the effect of metal composition cannot be discarded as it is well known that the presence of other metals can change significantly the Pb resistance to oxidation.

A whitish crystalline-like coating was observed on the surface of the painting "Incendio", 1990, produced by Emmanuel Nassar and awarded at the 6th Biennial of Cuenca. This work belongs to the Contemporary Art Museum of the University of Sao Paulo (MAC-USP) and such coating modified the artwork characteristics, causing an unpleasant effect and compromising its exhibition. The choice of the proper conservation and restoration strategies involves the understanding of the degradation process, demanding the identification of the chemical compounds formed on the painting surface, as well as of the other components in the painting. The results here obtained from Raman and optical microscopies, FTIR-ATR, SEM-EDS and GC-MS, revealed that the efflorescence chemical composition is almost only palmitic acid, with minor contents of stearic acid and their methyl esters, and that the paints are composed by chrome yellow, amorphous carbon and toluidine red pigment; an aluminum silicate filler in the black paint applied on the aluminum ground was also detected. Hierarchical Cluster Analyses (HCA) of the Raman spectra also revealed that the concentration of the efflorescence minor components depends on the paint composition. It was suggested, therefore, that the degradation process resulted from segregation and migration of mainly palmitic acid from the dried paints. Restoration methodologies used in similar cases, as well as factors that contribute to this process, were discussed.

In this work the effect of relative humidity (RH) and formaldehyde (H 2 CO) concentration on Pb corrosion was investigated; a possible synergism between the aldehyde and CO 2 effects was also considered. Triphasic aqueous salt solutions were used to produce 54% and 75% RH that, together with the 100% RH condition, were combined with 0, 0.62, 55 and 2.0 10 2 mg m −3 formaldehyde concentrations to compose the wanted environments. The results pointed to the conclusion that even at low RH (54%) formates are produced at the metal surface as a consequence of formaldehyde adsorption, indicating that the aldehyde has an active role in Pb corrosion; formates were also observed at relatively low H 2 CO concentration (0.62 mg m −3 ). No synergism between formaldehyde and carbon dioxide were observed as demonstrated by the Raman images from a corroded Pb coupon, showing that formate and carbonate contributions to the corrosion products were not spatially related. When compared to other volatile organic compounds (VOCs), formaldehyde harmful effect towards metals is frequently underestimated and the results here reported clearly indicate that, even at low RH, its concentration in indoor environments, where it tends to be produced and accumulated, has to be carefully controlled.