Conservation work aimed at securing the surfaces of the Domus Aurea decorated with plaster, wall paintings and stucco elements are proceeding in parallel with stability tests on architectural structures and environmental monitoring.
Overall, the decorative heritage of the monument consists of about 16,000 square metres of surfaces distributed among the various rooms, cryptoportica and passageways of which the Domus is made up.
Monitoring of the microclimate has been underway for many years. We must ensure that temperature/RH levels are as stable as possible. Variations in the microclimate cause the water present in the structures to evaporate, triggering the formation of salt efflorescences and above all leading to a risk of significant losses of materials and paint layers. The rehabilitation project therefore involves the detailed mapping of all the apertures present in the rooms of the Domus, drawing up a provisional isolation plan aimed not only at containing airflows but also at closing the most direct entry routes for rainwater. To this end, we have progressively and provisionally closed the apertures: the modern holes or skylights present in the vaults have been sealed with rigid covers fixed to zinc-coated frames. Polyethylene sheets have been placed over windows, doors and walls, fixed to frames made of treated wood; where it was essential to allow people to pass, we used vertical strips of polyethylene.
For safety reasons, and to allow us to diagnose the state of conservation, we also proceeded to light the areas still lacking light sources by installing lighting systems designed by an ISCR expert of a type that does not encourage the development of microorganisms on surfaces or compromise the chromatic stability of the decorations,. At the time of writing (July 2012), we are preparing a second batch of this lighting system.
Alongside the interventions described, we have begun a study aimed at defining a methodology for intervention and the choice of the most suitable materials for securing plaster, wall paintings and stucco elements. The study was carried out in the West Wing with a small pilot worksite on the west wall of Room 24, under the scientific direction of Mibac’s ISCR.
Each intervention is preceded by a campaign of fact-finding studies for graphic and other forms of documentation and the mapping of chemical, physical and microbiological decay.
This room is of considerable importance within the East Wing since, like the other five-sided courtyards facing south towards the artificial lake, it forms the external facade of the palace. Its decorations are identical to those chosen for the large internal halls: the walls must have been clad in marble panels, as indicated by the mortar on which they were laid and the holes where they were held in place. On the uppermost part, subjects reminiscent of theatrical scenes are superimposed on frescoed landscapes inside stucco frames; between pillars and little stucco columns are various figures in relief of different sizes shown in perspective. Ida Sciortino
Between December 2010 and September 2011 we carried out some interventions to secure and maintain the decorated surfaces in this part of the East Wing, covering about 80 m2 of decorated surfaces with painted plaster and stucco reliefs.
The preliminary phase involved collecting samples for laboratory tests to determine the nature of the biological patina and salt efflorescences.
Operations continued with a biocide treatment, effected by applying the products selected on the basis of analyses using sprays or cotton buds. The remaining biological patina was then removed using cotton buds and demineralized water, scalpels and nylon brushes.
This was followed by operations to extract soluble salts and remove the soil deposits still present on the surfaces.
Work proceeded with consolidation operations to readhere the detachments present between the decorated surfaces and the preparatory layers, and between the latter and the wall structure.
This operation was carried out in several stages, gradually injecting small quantities of material to avoid overburdening the detached parts; up to a week passed between one cycle of injections and the next to allow the injected substance to set.
The next operation was the treatment of the metal inserts, carried out by brushing them and applying isolating acrylic resin with a brush.
Finally, we proceeded to plaster and microplaster cracks and gaps, using mortars whose composition and granulometry was identical to the originals.
Work carried out by Società AREA Snc.
Room of the Owls 29
This is a vast reception hall, a triclinium, facing onto the centre of the courtyard of the West Wing, where there must have been a fountain, similar (or even identical, according to some scholars) to the large porphyry basin now in the Rotonda del Belvedere in the Vatican. The room takes its name from the owls, symbols of Athena, which appear alongside depictions of the goddess in the first of the five concentric rectangles into which the painted decoration of the vault is divided. The rest of the decoration repeats the whole “grotesque” repertoire: male and female figures, little animals, landscape paintings, chandeliers, vases and plant elements are arranged on a white background in the various registers, subdivided by soft drapery. Here too the walls, like the floor, were clad in marble.
Between June and October 2011 we completed work to secure the decorated surfaces of the vault of the Room of the Owls.
Again, we carried out a preliminary campaign of laboratory tests to guide our choice of products and techniques for each intervention: treatment to eliminate biological attack, revision of earlier interventions and removal of unsuitable metal elements, repair of adhesion and cohesion defects, plastering of gaps and cracks.
The plasterwork of the vault and its preparatory layers were readhered by injecting a product specially formulated for this purpose, composed of a mixture of hydraulic binders and inert powders with a low specific weight. A completely detached and cracked portion of plaster was secured by inserting a series of pins in polypropylene fibre, placed at intervals of 50 cm from one another to form an anchorage grid, inside which the consolidant was later injected.
A preventive biocide treatment was carried out after the intervention.
Work carried out by the company belonging to the conservator Marina Furci.
A long corridor currently closes the large courtyard-garden in the West Wing of Nero’s palace to the north. The results of the 2011 excavation campaign showed that the courtyard’s northern edge originally consisted of a simple but massive wall built to contain the earth of the hill behind and isolate the whole complex; at a later point the passageway was created by constructing a second wall parallel to the first and building the vault, pierced by skylights. The fresco decoration of the vault is subdivided into geometrical frames containing plant and animal motifs on a light-coloured background, identical to the fantasy repertoire depicted on the vaults and walls of the other large corridors in the East Wing.
In spring 2012 we completed the first batch of interventions to secure the decorations in Room 19, the so-called Small Cryptoporticus.
We first had to remove the calcareous encrustations covering large portions of the painted surface.
Consolidation work covered: the painted plaster preserved on much of the vault’s total surface area (c. 60 m), then the few remaining fragments of the stucco cornice at the impost of the vault.
On the walls, we proceeded with the operations needed to readhere the preparatory layers of the lost decoration, present, though in a discontinuous way, on both sides along the whole length of the room.
Finally, we consolidated the painted plaster and preparatory layers preserved in the lunettes above the room’s entrances.
Here, too, we readhered the plaster of the vault and its preparatory layers by injecting the same mixture previously used in similar situations.
For detachments on the walls we used a similar product, with heavier aggregate; for very extensive detachments we chose a product with a lower capability of diffusion inside the wall to avoid overburdening the structure with an excessive addition of consolidant. Edges, gaps and cracks were plastered using mortars similar to the originals in terms of components, colour and aggregate size (granulometry). During consolidation work, it was sometimes necessary to support the areas to be treated by propping them or using a protective coating obtained by applying several layers of cotton gauze. .
All the interventions carried out in this project phase are aimed at securing the decorated surfaces of the Domus Aurea and therefore do not involve cleaning work. However, in some cases we thought it useful to carry out small cleaning tests that, in addition to demonstrating the paint layer’s high potential for recovery, also provided detailed information on the time needed and the systems to be adopted to remove encrustations on top of the paint layer.
Work in Cryptoporticus 19 was carried out by the company ROMA Consorzio.