In 1619/20 Federico Borromeo gave order to modify the decorative apparatus of the church because it wasn’t anymore concordant with the cultic needs of the time. While waiting to have the money to execute decorative apparatus that suited with the given directives it was decided to cover the paintings first with a whitewash and subsequently with plaster. The operation was led in a wrong way and it caused remarkable damages to the painted surfaces adding lacunas and detachings to those caused by the hammering that had been carried out to apply the plastering.
Therefore, conservation and restoration interventions were necessary for the murals in the apse and the triumphal arch of the church of Santa Maria della Misericordia, which initially led to the re-adhesion to the load-bearing structure of the detached layers of painted plaster. Dull layers were removed with ammonium carbonate packs and finishing with ultrasound and scalpel.
At the same time, all the detached or raised fragments of color were consolidated by injections or diffusions through sheets of Japanese calcium caseinate paper. The saline efflorescences were first treated with ammonium carbonate, and subsequently with barium hydroxide. Finally, the retouching was performed with watercolor colors with the hatching technique.