Relating volatiles analysis by GC\u2013MS to Oddy test performance for determining the suitability of museum construction materials

Abstract

Conservators’ decisions regarding the suitability of museum construction materials for use in proximity to artworks still rely heavily on accelerated corrosion tests like the Oddy test despite widespread criticisms. These issues include inconveniently long wait times, sensitivity to only those pollutants capable of tarnishing metals, a general sense of unreliability, exaggerated environmental conditions, and subjectivity in assessing the test’s results. Increasingly, alternative strategies that use instrumental approaches involving volatiles sampling coupled to gas chromatography with mass spectrometry (GC–MS) are being explored as faster, more comprehensive, potentially quantitative, and possible more ‘objective’ means of assessing the dangers of off-gassing from museum construction materials. While many of these characteristics are now well documented, the objectivity of the instrumental result is arguable. While the detection of volatiles and semi-volatiles by GC–MS can confidently yield a list of potential pollutants, “chemical intuition” must be used to predict whether many of the emitted compounds can in fact adversely affect artwork. In this study, evolved gas analysis (EGA) coupled to GC–MS is used to predict the suitability of a small sample set of plastics for use in a museum. The potential impact of volatiles observed in the EGA chromatogram was assessed using chemical reactivity principles and the sparse literature data on the material damages caused by a small group of known pollutants. These same plastics were then tested using the British Museum’s 3-in-1 Oddy test. The prediction based on an educated chemical assessment of the compounds identified through instrumental analysis shows good correlation with pooled results from the Oddy test. In one of the two instances of disagreement, the EGA analysis was actually overly conservative and leaned toward prohibiting or restricting a material that passed the Oddy test. In the other, a material that failed the Oddy test but was passed by instrumental analysis was later shown to contain VOCs that could be considered corrosive. This trial suggests that with practice and experience instrumental approaches may be useful to supplement and perhaps one day supplant traditional accelerated corrosion testing of museum construction materials.