Impact Loads of Air Pollutants on Paintings: Performance Evaluation by Modeling For Microclimate Frames

Abstract

Modeling of the transport (fluxes) of gaseous air pollutants to the surfaces of paintings installed inside six different microclimate frames (mc-frames) was performed. Mc-frames are used to protect paintings against the external environment and to provide climate buffering. However, some can trap potentially harmful gases, especially acetic acid, which may be emitted inside the frames. A steady-state mass balance model was used to evaluate how changes in three factors (the ventilation rate, the volume of the mc-frame, and the inclusion of a pollutant absorber) would affect the concentrations of gaseous air pollutants transported to the paintings in the frames. The modeled impact to the paintings was determined to be higher inside than outside for two of six mc-frames when exposed to a 50/50 mixture of acidic (acetic plus formic acid at 100 μg/ m 3 ) and oxidative gases (nitrogen dioxide plus ozone at 2 μg/m 3 ). The concentrations of the pollutants were selected to provide clear degradative effects on the paintings. The modeling indicated the most effective way to reduce the potential pollutant impact on paintings in mc-frames is to reduce both ventilation and volume, and to also install a pollution absorber.