The process of restoration
THE RESTORATION AREA
The restoration work, spanning from March 2014 to April 2015, foresees the presence of an average of 12 restorers and approximately 35,000 hours of work. Gasparoli s.r.l. performs the restoration of the surfaces (plaster, stone elements, stucco, decorative concrete), while all the work related to the scaffolding, temporary works and site installations is performed by Impresa Percassi s.r.l.
The addressed surface is approximately 14,000 square meters in size, divided in plastered, decorative concrete and stone surfaces. More specifically, the plastered surfaces are those related to the parts of the recesses while the decorative concrete surfaces make up the frames beneath the walkways and all the decorated elements above them.
The stone surfaces are used for all the wainscots, the arches overlying the shop windows, the lower level window frames (beneath the walkways) and consist respectively of pink Baveno granite and Viggiù stone and Vicenza stone for the arches above the windows and the window frames.
A SITE OF ‘KNOWLEDGE'
Before the restoration work began, an experimental site in one of the arms of the Galleria towards Via Ugo Foscolo was set up, where in-depth surveys were carried out in order to build a data storage containing the results of specific on-site analysis, which tested the physical and chemical features of materials, their state of conservation, any degradation-related condition and any evidence of previous treatments.
In particular, the stratigraphic investigations have allowed to trace back the different colours in which the building has changed over time. Finally, we proceeded to perform a series of cleaning, consolidation and colouring trials on the stone surfaces in order to identify the most appropriate intervention methodology to ensure their preservation and the recovery of the ancient colours.
Thus during the restoration work the Galleria was transformed into a site of knowledge: an unique opportunity to uncover ancient construction techniques, operative schemes and the “know how” of workers and technicians, who have sedimented over 150 years and have made this Milanese monument unique. The extensive wealth of knowledge that has come to light, which has been collected and organized following scientific cataloguing methods, constitutes the basic reference for any future historical and critical study on the Galleria and new intervention hypotheses.
THE RESTORATION WORK
Removal of dust by means of dust extractors.
Dry cleaning with erasers and in-depth consolidation to allow the re-adhesion of any plaster portion that has detached from the sub-stratum.
Cortical consolidation of the outermost plastered surfaces.
Surface glazing, using different layers of silicate tints and earth colors.
Decorative concrete surfaces
Removal of any layers of incoherent dust, using soft-bristle brushes and dust extractors.
Surface dry-cleaning, performed through a slight friction of special erasers, in order to remove surface deposits, consisting of greasy fumes and dust, which are relatively coherent and adherent to the surface.
Grouting the cracks using specially formulated putty made with low salt content hydraulic binders, very fine washed sand and powdered marble.
Chromatic integration of surfaces with drafting whitewashed watercolours, to match the colour of the decorative cements with that of the adjacent stone surfaces.
Pre-consolidation, where necessary, of particularly ruined surfaces, through the application of a strengthening product applied by spray, brush or wraps.
Removal of incoherent superficial deposits consisting of powders that have sedimented on the surface through the use of soft-bristle brushes and recovering dust through dust extractors.
Cleaning differentiated by type, depending on the conservation conditions of the surfaces: with a micro- aero- abrasive system, consisting of small crystals of Australian almandine garnet, in which particles are adequately sized depending on the type of the support, sprayed at very low pressure by suitable equipment, which allows to obtain a delicate cleaning and to maintain natural patinas. Alternatively or in combination with these methods, cleaning with carbonate ammonium wraps in paper pulp is also possible.