Scientific examination of the Mantegna's paintings in Sant'Andrea, Mantua: the families of Christ and St.John the Baptist and the baptism of Christ

The attribution of the paintings to Mantegna has been the subject of many controversial discussions among art historians, even though today it seems that, in spite of the fact that the paint surfaces were already badly cleaned and varnished since the beginning of the nineteen century, both paintings can be attributed to the last period of Mantegna’s painting activity. Therefore, with the purpose to complement the historical studies with the results of scientific examinations, the two paintings have been analysed in situ with the use of non-invasive portable analytical techniques, such as digital multi spectral scanner imaging system and X-Ray Fluorescence. It has been hence possible to evaluate the state of conservation, study applied artistic technique, distinguish and locate past restoration interventions and analyze colour and pigments. This has been particularly done by complementing the chemical information gathered through the use of XRF with the false-colour IR technique. The first analytical results seem to confirm that both canvas paintings have been prepared in the usual way with layers of gesso; the contemporary presence of elements such as Fe, Si, Mn and Al can be associated with the use of umber mixed with red ochre pigments. Mantegna was a supremely confident draughtsman and there is no evidence in his underdrawings of the use of any aids for the reproductions of cartoons or the enlargements of studies on paper. Instead, he seems to have drawn directly on the gesso making his first marks with a brush and very diluted carbon black ink, perhaps guided by a smaller scale sketch on paper. Once the placement of the main features was settled, Mantegna developed the underdrawing using a darker more pigmented liquid material still applied with a brush and contours were defined with broad, thick and fluent lines which have been also painted at sight. The modelling of forms has been achieved at the level of painted surfaces which seems to be a further indication of Mantegna’s late painting production. All these features seem to be present in both paintings. Particular attention was paid to the understanding of the material composition of the flesh paints. In fact, even though their composition resulted to be composed of lead white with different proportions of vermilion, they show different flesh tonalities such as the case of St Joseph and Zacharias and Christ and St John in The Families of Christ and St John the Baptist (under the name of Holy Family). To this regard the presence of possible pigment deterioration processes which may have taken place in the past are presented and discussed

ATR and transmission analysis of pigments by means of far Infrared Spectroscopy

In the field of FTIR spectroscopy, the far infrared (FIR) spectral region has been so far less investigated than the mid-infrared (MIR), even though it presents great advantages in the characterization of those inorganic compounds, which are inactive in the MIR, such as some art pigments, corrosion products, etc. Furthermore, FIR spectroscopy is complementary to Raman spectroscopy if the fluorescence effects caused by the latter analytical technique are considered. In this paper, ATR in the FIR region is proposed as an alternative method to transmission for the analyses of pigments. This methodology was selected in order to reduce the sample amount needed for analysis, which is a must when examining cultural heritage materials. A selection of pigments have been analyzed in both ATR and transmission mode, and the resulting spectra were compared with each other. To better perform this comparison, an evaluation of the possible effect induced by the thermal treatment needed for the preparation of the polyethylene pellets on the transmission spectra of the samples has been carried out. Therefore, pigments have been analyzed in ATR mode before and after heating them at the same temperature employed for the polyethylene pellet preparation. The results showed that while the heating treatment causes only small changes in the intensity of some bands, the ATR spectra were characterized by differences in both intensity and band shifts towards lower frequencies if compared with those recorded in transmission mode. All pigments' transmission and ATR spectra are presented and discussed, and the ATR method was validated on a real case study