Territory and related artworks: stuccoworks from the Lombard lakes

The paper presents the analytical campaign carried out on the Baroque stucco decorations by Italian artists known as Artists of the Lakes. Forty samples (from moldings, background, sculpture bas- and high- reliefs) from the churches of S. Lorenzo in Laino, S. Maria dei Ghirli in Campione d'Italia and S. Maria Assunta in Puria (Como, Italy) were analyzed by chemical and mineralogical techniques and the data were discussed with a multi-disciplinary approach with art historians, in order to enlighten and compare the artistic techniques. Binders, aggregates, pigments and organic fractions were determined using optical microscopy, scanning electron microscopy with EDS microprobe, X-ray powder diffraction, Raman and Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry. The substrate is constituted by a mixture of magnesian lime, silicatic and/or carbonatic aggregate. Layers sequence varies from the simple pattern of S. Maria dei Ghirli (1 or 2 layers), to the complexity of S. Lorenzo where up to 9 layers above the substrate were observed. Pigment particles were identified as ochres and as green earth in a single case. Three different gilding techniques are described, as the gold leaf is applied over a chrome yellow ground (a missione), over a layer composed by ochre and lead white or over a brass leaf. In some cases organic materials were recognized: oil in gilding preparations and egg mixed with ochre pigments. A carbon black based pigment was identified by Raman spectroscopy in some decorative motifs. The sequence and composition of the finishing layers, the accumulation of particulate matter and the use of gypsum on purpose depending on the decorations typology, enlightened the artist skills, showing how different needs and timing influenced the commissions in the buildings.