AIC's 47th Annual Meeting

In recent years we reported a novel optical sensor based on silver nanoparticles and several applications in art conservation. The sensors are thin layers of silver nanoparticles (average diameter around 10 nm) deposited on a glass cover slip. Because of its large surface area versus volume, reactions on silver nanoparticle surfaces can occur quickly, making the sensor very sensitive, because of its strong optical absorbance and bright yellow color, evaluation of the extent of nanoparticle reaction can be easily done with visual inspection and quantitative spectral measurement, because it is composed of silver, it signals the potential risks to silver metal from pollutants in ambient air or off-gassing from housing and shipping materials. The sensor has been demonstrated to be useful as a substitute for silver metal coupons in Oddy tests and as an indicator of pollutants in the micro-environments created inside cases for Daguerreotypes. Here we reported an application of the silver nanoparticle sensor to monitor the air quality in metals storage for silver objects and photography storage for gelatin silver prints and daguerreotypes. Using a portable UV-vis spectrometer, the reactions of the silver nanoparticles could be monitored on site. In the first case study, the air quality inside display and storage cabinets for silver objects at the Margaret and Angus Wurtele Study Center of the Yale University Art Gallery was evaluated. These cases use a dedicated active ventilation system designed to purify the supply air and condition it to 30% RH before delivering it to the cases. To assess the cleanliness of the air and its safety for the silver objects, silver nanoparticle sensors were placed into a metal storage cabinet and a glass display case as well as in the room outside the cases for comparison. After 5 weeks the sensor response demonstrated that the ventilation system had maintained a much cleaner ambient condition inside those cases than in the surrounding room. After corrosion intercept and silica gel were introduced into those cases, another evaluation with the silver nanoparticle sensors showed the air cleanliness inside the cases was further improved. In the second study, the air quality was assessed in rooms at the Yale University Art Gallery that were currently used for photography storage as well as in other spaces into which those collections were to be moved. Silver nanoparticle sensors were deployed in those areas and measured after 1 week and 5-week exposures. The evaluation showed that air quality in the current photography storage rooms was similar to that in the study center described above, and the level of reactive air pollutants in the planned future storage rooms was not substantially greater than in the current storage rooms. Silver nanoparticle sensors were also used to assess air quality and safety in photography storage cases – solander boxes. Overall, the silver nanoparticle sensors have proven to be rapid, inexpensive screening tools that can be used to identify hazardous air quality environments and to compare environments intended for the storage and display of silver objects and photography collections.