The Pallavicini Palace, located in the center of Bologna, is an articulated architectural complex that develops between via dè Coltellini and San Felice. The current architectural configuration is the result of a series of successive operations of edification and modification both in the structure of the building and in the interior decorations.
On the front of Via San Felice is possible to identify three distinct buildings incorporated in the current façade by Alessandro Amadesi in 1788. From that date Alessandro Amadesi, in addition to intervention in façade, make also a series of changes of the interior (including also the apartments on Via San Felice) with rich decoration in all the rooms that follow one another behind the main façade.
The decorations are part of the restructuring plan desired by Count Giuseppe Pallavicini that, in 1775, became the owner of the building already leased since 1765 by the father (figure 1).
The paintings of the vaults are largely inspired by the classicism of Pallavicini who was in close contact with the most advanced circles of the late European Enlightenment and influenced by Carlo Bianconi (figure 2).
Due to the complexity of the decoration it was necessary to provide a thorough and accurate analysis made through:
1. Photomap and detailed photographic campaign
2. Degradation map of the decorated surface
3. Laboratory analyses on samples for identification of the physical characteristics of the materials and of the pathologies and causes of degradation
4. Historical research
5. Stratigraphic analysis of the coatings for the identification of the layers sequence such as paintings, decorations, plasters, finishes
6. Restoration samples performed on small portions to test the effectiveness of some interventions and to verify at this stage how methodology is the most correct.
In the context of the restoration project of some rooms in the piano nobile of Palazzo Pallavicini, was performed an autoptic and stratigraphic analysis campaign functional to define the precise type of coating layers that have characterized the surfaces of the interior area during time, identifying the materials and techniques used. A particular attention has been given to the finishing attributable to interventions which led to the creation of the decorative stucco and painted surfaces of the vaults and walls (figure 3).
The executive techniques
It was also possible to make some observations on the technical execution of the wall paintings and stucco through: autoptic analysis carries out with reflection and oblique light, the information derived from the historical research and the data obtained from laboratory tests carried out on samples taken in the various rooms. These informations are fundamental for the evaluation of the state of conservation and subsequently to choose the right restoration method.
The paintings that decorate the vaults of several rooms seem to be executed mostly “a secco”, but the good water resistance would suggest “mezzo fresco” or a lime paint; traces of underdrawing would direct towards a mixed technique with frescoes basis and dry finishing (as indeed seem to confirm the laboratory analysis). The paintings are made on plaster of lime and sand above which identifies a kind of “scialbo” calcium carbonate and gypsum based.
The stuccoes are made with mixtures based on gypsum and lime with the addition of sands for the support layers.
Stratigraphic analysis of coatings
The samples of the stratigraphic analyses were performed at the surface of decorative stucco and painted plaster of the walls both in the decorated rooms that in the south wing with no decorations.
In the case of Palazzo Pallavicini this methodological approach was particularly useful to get a significant synthesis about finishes during the various phases of construction and development: from the interventions before the eighteenth century to the reorganization and the architectural style of the late 1700s.
The stratigraphic analysis carried out at the surfaces of the decorative stucco and painted surfaces led to identify three macro-periods (figure 4) of activity that can be summarized as follows:
_ Period 1 | XX century: it is currently the layers visible, interpretable as recent maintenance work for the position of the layers in the general stratigraphic sequence and in relation to the materials used (it is washable tempera of industrial production).
_ Period 2 | late XVIII century (1789-1793): these are the finishing layers correlated to the interventions that lead to the creation of the decorative stucco and painted decorations of the vaults and walls (dating to the years between 1789 and 1793, as revealed by the study of the historical documentation).
_ Period 3 | before the end of XVIII century: these are finishing fragments of monochromatic dark green and a polychrome decoration in architectural composition identified on the walls of the south wing of the building. These finishes have been identified immediately below the layers dating to Period 2: the position of the layers in the general stratigraphic sequence therefore leads to date the third period to an earlier time than the interventions of 1789-93.
THE ANALYSIS OF CONSERVATION PROBLEMS AND THE DEGRADATION OF THE INDIVIDUAL ROOMS
The survey was conducted on all decorated surfaces of rooms object of intervention. In general it was possible to identify the following main categories of problems (figures 5-6):
_Infiltration problems: related to the stagnation water caused by percolation of rain from the top, they are mainly correlated to the presence of salts, which have caused the dete rioration of the paint surface and the plaster support. Laboratory analysis have identified the presence of nitrates and sulfates.
_Problems related to the painting technique: the realization of large portions painted “a secco” on a fresco base caused the exfoliation of the paint, this problem is mainly located in “Sala dei Conviti o degli Specchi” where large portion of the paint were made “a secco” probably to harmonize the different phases of intervention.
RESTORATION PROJECT OF THE DECORATED SURFACES
On the basis of materials typology present in the rooms is possible to identify three areas of intervention: the paintings of vaults and walls, stuccoes and plaster walls (that preserved the original finishes of the rooms as verify in the stratigraphic analysis performed directly on the different surfaces).
For the detailed choice of the restoration methodologies (in particular for the consolidation and cleaning phase) were made some samples directly on the surfaces in the different rooms. The datas relating to the objectives of the various tests, the methodology (in relation to products, equipment and the executive techniques used) and the results were recorded directly in specific schedule in situ, then digitized and accompanied with photographic documentation (figures 7-8-9).
[by Rossana Gabrielli]