Automated characterization of varnishes photo-degradation using portable T-controlled Raman spectroscopy

Abstract

In this work, a portable-Raman device (excitation wavelength 1064nm) was employed for the first time for continuously monitoring the complex molecular dynamics of terpenoid resins (dammar, mastic, colophony, sandarac and shellac), which occur during their ageing under artificial light exposure. The instrumentation was equipped with a pyroelectric sensor allowing for temperature control of the sample's irradiated surface while the acquisition of spectra occurs by setting fixed maximum temperature and total radiant exposure. Resins were dropped into special pits over a dedicated rotating wheel moved by a USB motor. The rotation allowed samples sliding between the positions designated for the acquisition of the Raman spectra and that for artificial ageing. Samples were exposed to artificial light for 45-days and almost 400 spectra for each resin sample were collected. The exposure to artificial light led to significant changes allowing the characterization of the alteration process. The automated acquisition of a large number of spectra overtime during light-exposure has given the possibility to distinguish fast dynamics, mainly associated to solvent evaporation, from those slower due to resins photo-degradation processes.

Warm white LED lighting in museums: Ageing effects on terpenoid resins assessed through Raman spectroscopy and chemometrics

“…Whereas in shellac intensity changes in the C═C stretching region are less evident because unsaturated chemical bonds are fewer in number and located in the side chains with respect to colophony. Moreover, intensity decrease between 750 and 1,400 cm −1 are mainly ascribable to ethanol evaporation process as it was noticed elsewhere …”

“…Raman spectroscopy system was employed to assess molecular changes occurring in resins structures during both dark and light ageing. This spectroscopic technique has been increasingly employed for studying the complex alteration dynamics of artistic organic compounds such as resins, colourants (lakes), lipids (siccative oils), and proteins (binding media), due to its high sensitivity to carbon–carbon single and double bonds. In particular, here, a home‐assembled portable Raman scanner (excitation wavelength 1,064 nm) has been used in order to automatically monitor the ageing process collecting a periodic sequence of spectra in the same area of analysis.…”

Detection of the Glass Transition of Polymers Used in Art and Art-Conservation Using Raman Spectroscopy

“…Vibrational modes assignments of Raman bands of colophony shown in Fig. 3 are listed in table 3 in accordance with the literature [9]. Figure 4 reports the weighted averages of the peak position between 1600-1630 cm -1 of colophony as a function of temperature.…”

Fluorescence Lifetime Phasor Analysis and Raman Spectroscopy of Pigmented Organic Binders and Coatings Used in Artworks

“…The most intense peak in linseed oil (dried for 48 h, at room conditions) was at 1658 cm −1 , associated with the stretching vibration of a cis dialkyl C=C double bond in linoleic acid [36,37]. As to the mastic resin, the main Raman signals were revealed at 1441 cm −1 -with a shoulder at 1461 cm −1 -and 1652 cm −1 , corresponding to δ(CH 2 ), v(CH 2 ), and v(C=C), respectively [38][39][40][41]. No bands associated with C=C vibrations were detected in the Raman spectrum of beeswax.…”