FTIR study of ageing of fast drying oil colour (FDOC) alkyd paint replicas

TitleFTIR study of ageing of fast drying oil colour (FDOC) alkyd paint replicas
Publication TypeJournal Article
Year of Publication2014
AuthorsDuce, C, Della Porta, V, Tiné, MR, Spepi, A, Ghezzi, L, Colombini, MP, Bramanti, E
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
ISSN13861425 (ISSN)
KeywordsAcetic acid, Alkyd paints, Artificial ageing, Atmospheric pollutants, ATR FTIR, ATR-FT-IR spectroscopy, ATR-FTIR, Auto-oxidation reaction, Color, Crosslinking, Drying oils, Fourier transform infrared spectroscopy, Natural ageing, Paint, pH, Photodegradation, Spectral change, Spectroscopy, Stretching

We propose ATR-FTIR spectroscopy for the characterization of the spectral changes in alkyd resin from the Griffin Alkyd Fast Drying Oil Colour range (Winsor & Newton), occurring over 550 days (∼18 months) of natural ageing and over six months of artificial ageing under an acetic acid atmosphere. Acetic acid is one of the atmospheric pollutants found inside museums in concentrations that can have a significant effect on the works exhibited. During natural ageing we observed an increase and broadening of the OH group band around 3300 cm-1 and an increase in bands in the region 1730-1680 cm-1 due to carbonyl stretching. We found a broad band around 1635 cm-1 likely due to CO stretching vibrations of $\beta$ dichetons. These spectral changes are the result of autooxidation reactions during natural ageing and crosslinking, which then form f alcohols and carbonyl species. The increase in absorbance at 1635 cm -1 was selected as a parameter to monitor the ageing process of paintings prepared with FDOC, without the need for any extractive procedure. FTIR spectra of paint replicas kept under an acetic acid atmosphere indicated the chemical groups involved in the reaction with acid, thus suggesting which spectral FTIR regions could be investigated in order to follow any degradation in real paintings. A red paint sample from a hyper-realistic artwork ("Racconta storie", 2003) by the Italian painter Patrizia Zara was investigated by FTIR in order to evaluate the effects of 10 years natural ageing on alkyd colours. The results obtained suggested that after the end of chemical drying (autooxidation), alkyd colours are very stable. © 2014 Elsevier B.V. All rights reserved.