The ageing behavior of phenol formaldehyde (PF) foam, a material increasingly used in modern-contemporary art, was investigated by a multi-analytical approach. PF foams with open- and closed-cell structures were selected and analyzed in their unaged and naturally indoor-aged state by employing optical microscopy (OM) and fiber optical reflectance spectroscopy (FORS) for assessing their morphology and color alteration. Micro-Fourier transform infrared spectroscopy (μ-FTIR) was used for determining chemical changes and oxidation processes, and the acidity was monitored by pH measurements. The results clearly showed the extreme sensitivity of both open- and closed-cell PF foams to conditions typically found in indoor museums. OM indicated that the cells of the foams are prone to disrupt, and a tendency towards a red color shift was observed with FORS. μ-FTIR revealed the formation of quinone groups resulting from oxidation reactions. Finally, a slight decrease in the acidity was found by pH measurements.
Keywords: ageing; modern-contemporary art; optical microscopy; pH; phenol formaldehyde (PF) foam; µ-FTIR.