This study examines some of the degradation phenomena exhibited by modern oil paintings and twentieth century oil paint formulations and possible correlations with the various organic additives typically introduced by manufacturers. The research takes into consideration historical and modern tube oil paints produced by different European manufacturers and selected twentieth century oil paintings which showed degradation problems such as efflorescence, softening, cracks and sensitivity towards water and polar solvents. The composition of oil paints and paintings samples was studied with XRF, SEM-EDX, ATR-FTIR and GCMS. The results showed that both artists' oil paints and paintings samples contain a complex mixture of additives to the oil binders and pigments. The presence of aluminium and zinc stearates, added as dispersion agent gelling agents, was detected in most paint formulations of HKS, W&N, Talens and Maimeri (c. 1940-present). Several paint films showed an unusually high content of fatty diacids, suggesting that, in drying, an oxidative reaction was favoured above polymerisation. This occurrence, together with the diversity of lipidic media, additives, pigments and driers present in the industrial formulations could play a crucial role in paint failure and instability, as showed by the analysed case studies. The obtained results may help understanding the behaviour of modern oil paints and painting surfaces and contribute to improved conservation methods.

a b s t r a c tDuring the 20th century, many innovative binders have been rapidly introduced to the art world and soon became popular as artists' paints and pictorial media. However, despite the advantages that new synthetic materials presented, oil paints have never been entirely substituted. Indeed, this paper focuses on the results provided by the scientific analysis of a group works from the oeuvre of Lucio Fontana , all of which created between 1960 and 1964 using oil-based media, and aims to illustrate how oils contained in the pictorial media have influenced these works' respective ageing and degradation processes. Despite the apparent coherence in the behaviour of many of Fontana's creations, some artworks revealed discrepancies in terms of the physical and mechanical behaviour of the pictorial films and in alterations resulting from degradation processes. Samples taken from case studies belonging to the Olii and Fine di Dio series were analysed using optical microscopy, X-Ray Fluorescence (XRF), FourierTransform Infrared Spectroscopy in attenuated total reflectance (FTIR-ATR) and Gas ChromatographyMass Spectrometry (GC-MS) in order to study and identify the materials employed by the artist and the products of their degradation processes. These analyses gave unexpected but useful results (such as the presence of non-drying or slow-drying oils in the paint formulations) which not only provided us with new insight into the nature of the constituent materials, but also facilitated the elaboration of correct conservation measures and suitable restoration interventions.

Specific analytical tools are needed to investigate the composition and degradation processes of the synthetic materials in the cultural heritage, and recent advancements in pyrolysis-based analytical techniques have great potential for the characterisation of synthetic polymers. We applied evolved gas analysis mass spectrometry (EGA-MS) and double shot pyrolysis coupled with chromatography and mass spectrometry (Py-GC/MS) to investigate polyurethane foam micro-samples from the Italian popart sculpture "Contenitoreumano n.1" (1968) by Ico Parisi (1916-1996) and Francesco Somaini (1926-2005. The chemical analysis aimed to assess the chemical composition and of the state of preservation of the PU foam by acquiring information on its thermal degradation behaviour and identifying the pyrolysis products produced at different temperatures. A preliminary ATR-FTIR analysis was also carried out. The multi-analytical approach enabled us to identify the isocyanate and polyol precursors as 2,6-toluenediisocyanate and polypropylene glycol, respectively. The plasticizers used in the production of the PU foam were also identified in the first shot of a double shot Py-GC/MS experiment. A comparison of a sample of better preserved foam with a sample of degraded foam from the surface of the object highlighted that the more degraded part of the PU foam featured an increase in the thermal degradation temperature of the soft-fragments of the PU network, related to crosslinking phenomena. Moreover, loss of plasticizers and formation of NH2 functional groups was observed in the degraded foam.

The first synthetic polymers were introduced as constituents of everyday life, design objects, and artworks at the end of the 19th century. Since then, the history of design has been strictly connected with the 20th century evolution of plastic materials. Objects of design from the 20th century are today a precious part of the cultural heritage. They raise specific conservation issues due to the degradation processes affecting synthetic polymer-based plastics. Museums and collections dealing with the conservation of design objects and modern materials need to base their conservation strategies on compositional data that reveal the formulations of historical plastics and their decay processes. Specific and specifically optimized analytical tools are thus needed. We employed flash analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS) and evolved gas analysis coupled with mass spectrometry (EGA-MS) to characterize “historic polymeric materials” (HIPOMS) and heritage plastics at the molecular level with high chemical detail. This approach complements non-invasive spectroscopic diagnosis whenever it fails to obtain significant or complete information on the nature and the state of preservation of the materials under study. We determined the composition of several 20th century design objects (1954–1994) from the Triennale Design Museum of Milan (Triennale Milano - Museo del Design Italiano), which for different morphological, chemical, or physical reasons were unsuitable for characterization by non-invasive spectroscopy. EGA-MS proved capable for the study of the different fractions constituting heterogeneous micro-samples and for gaining an insight into their degradation processes from the contextual interpretation of thermal and mass-spectrometric data.

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