Our restoration work in Palazzo Litta was part of the project of plant system upgrade of the noble rooms located on the first floor of the building. Prior and simultaneously to the realization of the drills necessary to the cable routing from one room to another, we secured the decorated plaster nearby the spot chosen for the passage. This portion of plaster had been treated in advance with soft-bristle brushes in order to remove the incoherent deposits and with synthetic sponges with high absorption. After executing an accurate control of the pictorical surface aimed at verifying its solidity and the eventual presence of lifted coloured scales or pulverisation phenomena of the material, we consolidated the pictorical film (where necessary) by applying synthetic resins used in emulsion. The consolidation of the pictorical film is followed by the consolidation of the supportive plaster and by the restoration of the adhesion to the underlying wall realised with an injection of premixed hydraulic mortar with low specific weight. Once concluded the consolidation, on the treated area we applied a support bandage in order to guarantee the solidity of the plaster during the following drilling phase. When the drill was made the electrician inserted the pipe for the passage of the cables and the restorers removeed tha bandage by cleaning gently the surface from every adhesive residual, grouted the lacunas and restored the colors using watercolors the selected part.