No abstract

Resins obtained from Pinus genus species have been widely used in very different fields throughout history. As soon as they are secreted molecular changes start altering their chemical, mechanical and optical properties. The ageing processes are complex and chemical and structural changes associated to resin degradation are not yet fully known. Many questions still remain open, for instance changes happening in pimaranes, one of the two diterpenoid constituents of the resin.A systematic study of the ageing process of Pinus resins is done through of Fourier Transform Infrared Spectroscopy (FTIR) using chemical standards and complementing obtained results with Gas Chromatography coupled to Mass Spectrometry (GC/MS) analysis when necessary. Moreover, long-term degradation processes are also investigated through the analysis of a selection of dated historical resins. The study overcomes the limitations of GC/MS and brings new information about the reactions and interactions between molecules during Pinus resin ageing process, providing information about bonds affected and unaffected and can be used as specific markers of the degradation and of the resins themselves.

Oil paints comprise pigments,d rying oils,a nd additives that together confer desirable properties,but can react to form metal carboxylates (soaps) that maydamage artworks over time.T oo btain information on soap formation and aggregation, we introduce an ew tapping-mode measurement paradigm for the photothermal induced resonance (PTIR) technique that enables nanoscale IR spectroscopyand imaging on highly heterogenous and rough paint thin sections.PTIR is used in combination with m-computed tomography and IR microscopytodetermine the distribution of metal carboxylates in a23-year old oil paint of knownformulation. Results show that heterogeneous agglomerates of Al-stearate and aZ ncarboxylate complex with Zn-stearate nano-aggregates in proximity are distributed randomly in the paint. The gradients of zinc carboxylates are unrelated to the Al-stearate distribution. These measurements open an ew chemically sensitive nanoscale observation windowo nt he distribution of metal soaps that can bring insights for understanding soap formation in oil paint.