Characterisation and monitoring of acidic emissions from marine archaeological wood

The marine archaeological collection at the Mary Rose Museum contains wooden and metal artefacts displayed inside the same environment. This project investigated acidic emissions from archaeological wood to evaluate if they could cause chemical damage to the metal artefacts displayed alongside. Thermogravimetric analysis (TGA) was used to quantify biopolymers within sound and archaeological wood from the Mary Rose Museum. In addition to good relative agreement with traditional methods, TGA detailed chemical changes of the biopolymers and interactions with PEG, which could be used to evaluate future treatments. Solid phase micro extraction-gas chromatography-mass spectrometry identified PEG treatment of sound wood near eliminated emissions by acting as an impenetrable barrier. In contrast, PEG treated wooden artefacts from the Mary Rose Museum emitted a greater array of compounds compared to sound oak, including acetic acid and sulfur compounds, which corroded pure lead and silver, highlighting that emissions from archaeological wood can accelerate metal corrosion. However, environmental monitoring inside display cases at the Mary Rose Museum identified no relationship between the presence of archaeological wood and accelerated lead corrosion. Rather, smaller cases had higher acidic concentrations despite the cases being modern and having sodium hydroxide impregnated activated carbon charcoal filters to remove acidic vapours. The causes of corrosion are complex and depend on other factors, such as case materials, filtration systems and surface area. To enable quick risk assessments of display environments, a real-time acetic acid sensor was developed. This self-contained, affordable device used lead oxide coated quartz crystal microbalances, which quickly reacted to acetic acid vapour at ppm concentrations. Moreover, the rate of signal change correlated with volume of acetic acid injected into the test chamber. Therefore, this sensor design has potential to monitor acetic acid build up inside cases and further development is recommended to increase the repeatability of this sensor