A new perspective on the study of microenvironments created by the backings on canvas paintings: Use of environmental pH sensors

Abstract

Currently, backings are widely used as a preventive conservation treatment for paintings on canvas. However, this kind of intervention promotes the accumulation of pollutants, which could be a risk to the chemical stability of the painting. Right now, the scientific research into this problem is limited. The main objective of our research is to use optical pH sensors to evaluate how the presence of pollutants and their interactions affect the air chamber’s characteristics. These were patented (P201003107) by the research group CERVITRUM (CSIC), and, at present, are the only technology capable of effectively measuring the pH of the air quantitatively and qualitatively. The application of sensors in our research project was carried out through an experimental study where we worked with 15 mock-ups in which different backing materials were placed. These were exposed to variations in RH and T that simulated an exhibition space without climate control. The main point of the workplan was to adapt the usual evaluation methodology of the sensors since, due to the characteristics of microspace, this cannot be followed. First, we tested different exposure times, and, after establishing the most suitable one for the objectives set, we made multiple evaluations to check its reproducibility throughout the 7 months of study. The results obtained have shown differences in the environmental pH that vary according to the material used as a backing. We detected variations of 0.1 units on the pH scale between paper, plastic sheets and boards derived from wood. This data has been repeated in the continuous measurements of each model. Therefore, the development of this project has allowed us to apply the environmental pH sensor as a quick, simple and efficient way to evaluate the impact of the accumulation of polluting gases behind a canvas closed with a backing. Compared to conventional analysis procedures, the major advantage of this new methodology is to determine the characteristics of the air chamber from a general perspective in which all its parts interact.