The case study of The daughters of the Emperor Ferdinand I by Jakob Seisenegger, in Trento (Italy): analytical hygro-mechanical results as a support in risk assessment for technical interventions

In this paper, a long-term monitoring experience on a panel painting, carried out using a whole set of analytical tools before the scheduled conservation intervention, is described. The object under analysis is a painting of the XVI century, “The daughters of the Emperor Ferdinand I” by Jakob Seisenegger, painted around 1534 and preserved in the storerooms of the Superintendency of the Trento Province and of pertinence of the Buonconsiglio Castle. The wooden support is built using many narrow planks of pear wood; some degradation evidences are visible, caused by insects and by the previous storing conditions. Old strong conservation interventions, when the present battened crosspieces structure was applied, have induced the non-optimal state of conservation as well. The panel painting has been monitored for some years in its storeroom, climatically uncontrolled for most of the time, using: displacement transducers, put in different positions, relevant from the structural point of view; microclimatic monitoring (temperature and relative humidity); mass variation monitoring, using an innovative differential scale able to measure the response of the panel to the fluctuations with an otherwise impossible resolution. The monitoring provided the experimental hygro-mechanical tendencies of the painting as a contribution in the design phase of the new crosspieces that will be applied to the panel and for the definition of the acceptable variations of the microclimate in the exhibiting site. The experimental data, coupled with a FEM modelling approach, allowed the characterisation of the individual response of the panel to fluctuations taking into account partial hysteresis. This research has been performed in collaboration with the Superintendency of the Autonomous Province of Trento.