Intervention
General conservation problems
Santa Lucia alle Malve, like most of Matera’s rupestrian churches, is a structure partly built and partly dug into the rocky bank; although it is not a completely hypogeal site, this condition of continuity with the mother-rock, and the related thermo-hygrometric parameters, are the main factors for the formation of salt efflorescence and the proliferation of biological species.
Inside the church, both the bare rock surfaces and those covered by the paintings, were therefore entirely disfigured by biological patinas, varying in colour from light green to dark almost black, to dark orange to brown. This biological proliferation continued over time, leading to a progressive degradation of the wall paintings in the church. To this inescapable intrinsic factor of alteration, were added those connected to the various periods of abandonment, or improper use.
The technical characteristics and conservation problems faced by the frescoes of Santa Lucia are common to most of the rock-hewn churches in Matera; separating the frescoes from the walls, resecting them, and moving them to another location, especially in the past, and under special conditions, seemed the only way to save them. Today this practice is only reserved for very serious, extreme situations of urgency.
The conservation choice, for the preservation in situ, was the one followed at Santa Lucia: articulated in several steps, the first of which was the disinfection of all internal surfaces. The current restoration of the paintings in the Church of Santa Lucia alle Malve is the last of five interventions from 1979 to the present.
The state of conservation of the painted surfaces, as for many other rupestrian churches in Matera, is closely linked to the natural alteration factors that characterise the environments excavated in the rocky banks: percolation of water, high levels of relative humidity, poor air movement. To these are added, and act in a synergetic manner, anthropic alteration factors: impacts, abrasions, breakage, over-addition of substances; sudden changes in microclimatic conditions related to use.
This last factor, moreover, in close synergy with all the others, while in past it was related to the church’s uses as a shelter and dwelling place, is nowadays mostly determined by the large and ever-increasing number of tourists. All of these elements are understandably critical for the proper preservation over time of a structure that is as precious as it is delicate, which is why continuous attention and regular maintenance are unavoidable.
External Intervention
The analysis of the conservative situation inside the church and the results of the diagnostic investigations, led to preliminary treatments of a general character, which were conducted prior to the restoration of the surfaces.
The first of these treatments was the improvement of rainwater runoff in the rocky plateau above the church. Here, minimal operations were carried out: the removal of weeds and debris; the sealing with traditional mortars of stone powder and NLH3.5 hydraulic lime of the water-permeable paths; the stabilisation, with the same type of mortar, of the hollows where the existing materials were most disaggregated; the replacement of a manhole cover to channel rainwater and the creation of two new drainage system for rainwater to prevent flooding of parts with depressions.
Intervention on paintings
For the restoration of the painted surfaces inside the church of Santa Lucia alle Malve, the biological problem was the first to be addressed. To this end, a disinfection treatment was carried out on the painted layers before any other intervention, aimed at devitalising microorganisms. In addition to patinas of biological origin, however, the frescoes were also found to be covered, almost uniformly, by whitish patinas, which were more or less transparent: efflorescence of soluble salts and calcareous concretions. Given the environmental conditions linked to external climatic variations, the alternating cycles of wetting and drying, due to infiltration or high air humidity, can be the cause of crystallisation phenomena on the surfaces of calcium carbonate and other soluble salts carried by water. The removal of the patinas of crystallisation of soluble salts took place during the restoration of the paintings.
Disinfection
The most immediately noticeable alteration was the considerable green and brown biological patina present on all surfaces, including the painted ones. These biological patinas are harmful not so much from an aesthetic point of view, but because of the disintegration they produce on the mortar and colours.
A preliminary stage to the disinfection treatment was the investigation for biological characterisation conducted on patina samples, which revealed the proliferation of microorganisms belonging to different species. There were two disinfection treatments: a preliminary one and one carried out one year after the first, after the restoration work had been completed, as part of the conservation programme. All surfaces were treated with a broad spectrum biocide, Preventol RI 80 at a concentration of 3% (V/V) in deionised water. The treatment comprised three application cycles at one-week intervals, as tested in the two pilot samples during the design phase. At the end of the three cycles, the degree of residual viability of the different species was checked.
Cleaning
The cleaning of the painted surfaces consisted of a series of operations aimed not only at removing whitish veils due to crystallised salts, but also the residues of substances applied during past restoration work.
Removal of the patina of crystallisation of soluble salts
The first tests concerned the wall of the Incoronazione della Vergine: they were conducted by applying ion exchange resins (Ionex H), whose immediate effect gave very satisfactory results, making the colours and details of the paintings legible. In order to limit the contribution of water as much as possible, before applying the ion exchange resins, in some cases the product Ciclometicone D5 was applied by brush, while in others a type of mechanical cleaning was preferred, obtained with silicon grinding wheels on an electric motor, which made it possible to remove carbonation and salt efflorescence without altering the delicate balance of the original materials.
Integrations
The adhesion of the frescoes to the rock is good, with detachment phenomena affecting very limited areas: consolidation was conducted here with infiltrations of pre-mixed mortar.
The colour integration phase, both of the plastered gaps and the abrasions of the paint film, was conducted with the use of Gamblin colours.
At the conclusion of the lengthy restoration phases, there was a full awareness that the natural environmental situation will impose a protocol of periodic maintenance practices; this brings Santa Lucia alle Malve into line with the other rupestrian churches of Matera. Left, after extensive restoration, without these good practices, they are all destined to soon return to their primitive condition.
