Statue of Aura

Description

This feminine figure majestically walks with her left leg in front and the right one flexed behind her.  An ankle-length tunic gently flows around her as she moves. Meanwhile, a mantel is wrapped around the central part of her figure. Originally, the mantle was supposed to appear lifted above her head, blown by the breeze.  Actually, the statue itself is a personification of the marine breeze, a subject from ancient Greece widely used to decorate the temples.  These were indicatively seen especially in acroterion statues, which adorned the apex of the pediments. It is, perhaps, precisely this acroterion figure that became a reference upon which our statue and others of the Roman era were modeled—all formed from Pentelic marble and dated sometime during the first century, A.D.

The original prototype is still sought after in Greece—probably the work of a simple attic sculptor who, highly influenced by Phidian art, was prolific in the last decades of the 5th century B.C.  In the rounded statues that adorn the Parthenon, the celebrated Athenian sculpture experimented with pliable innovative solutions to translate stagnant marble into moving drapery and ethereal garments. The cloth, as if it were wet, accentuates the female figure in a natural realistic style for the first time in ancient art. The statue of Aura, although a Roman replica completed a few centuries later, is still testimony to the grand artistic and cultural season that uniquely occurred in the city of Athens during the governing of Pericles in the 5th century B.C. after the victory of the Persians.

State of Preservation

The statue, headless, with mutilated arms and missing parts of its drapery, was located until the end of 2005 in an open-air niche (the second niche from the left on the south-facing wall of the Pinecone Courtyard). In 2005, in the course of a conservation campaign that also involved the other statues in the niches on the same side of the Courtyard wall (2015-2016), the work was brought to the Marble Restoration Laboratory where it was submitted to a restoration intervention.

Subsequently – based on conservation criteria and an assessment of the high quality of the sculpture - it was decided not to relocate the work to its place of origin in the Courtyard. For this reason, the work was subsequently admitted to storage, waiting to be shown to the public with the best possible result. The opportunity to finally place the work in the gallery permanently where the public could enjoy the work in all its beauty was presented only recently, and given this relocation, we realized that a new spontaneous alteration on the surface occurred during its stay in the warehouse (Magazzino delle Corazze), made a new conservative intervention necessary.

The marble had a visible dark chromatic alteration--intense brown, with halo effects, distributed on the frontal and lower area of the mantle drapery, which covers the lower part of the legs. The disturbing effect of this alteration increased because, from a visual point of view, there is a clear break between the lower, dirtier region and the cleaner-upper area of the front part of the statue.

In the preparatory phase of the restoration intervention, a photograph from 2010 was found of when the statue was in the warehouse, in which there are already evident signs of a chromatic alteration only five years after the conservative intervention, although with an extension and intensity less than as it appeared recently. In addition to a more routine check of the conservative conditions of the work, the visual lightening of this phenomenon was the primary purpose of the restoration. For this reason, before intervening it was necessary to go back to the causes of the phenomenon through analytical examinations, surveys on past events including restorations, and autopsy observations with the utmost precision to be able to adopt the best methodologies with the least possible number of tests to be performed directly on the work.The substance that covered the surfaces affected by the alteration was lacking in transparency because it appeared to have a certain thickness, sometimes reaching the effect of the film, while in other points showing edges with more nuanced contours which gave it an appearance of a "greasy" halo. Furthermore, the substance in question appeared to be firmly anchored to the marble surface that, on the other hand, showed an eroded and locally declined aspect in several places.

Restoration Procedures

Based on these accumulated substances, the first diagnostic step was to look for clear evidence of the presence in the area in question of organic substances, both natural and artificial. This first investigation showed the presence of patinas/incrustations based on iron oxides, also distributed outside the investigated area; moreover, drips on the back of a substance with a predominantly non-organic component were noted. We then moved on to try to detect the presence of biodeteriogens, and thanks to this investigation, we found traces of fungal, even if no longer active and in a not prevalent quantity. These deposits of biodeteriogens were correlated to the time the statue spent in storage since it was the ideal habitat for the development of fungi due to the high percentage of relative humidity. Furthermore, the rich presence of iron-based compounds on the statue, already noted on the occasion of the previous restoration, may have facilitated the fungus development (in this specific case Aspergillus Ochraceus) since iron is the main metabolite of this species.

This biological attack was not enough to explain the phenomenon under examination; we then moved on to more direct analysis of inorganic characterization (FTIR), the results of which resulted in a mixture of silicates (probably of magnesium) and iron and manganese oxides. While due to the presence of iron and manganese-based substances, it was possible to hypothesize, at least in part, original endogenous factors linked in some way to the lithotype for substances outside iron and manganese (silicates and magnesium). Since the range of hypotheses on the formation of the phenomenon persisted, we referenced what had already been tackled in the 2005 restoration, when the presence of iron (in that case on the whole surface) was much more evident following the display of the statue in external exposure and we had arrived to infer a presence of manganese through empirical tests with positive results using a compound based on hydrazine monohydrate and hydroxylammonium chloride at pH = 7 ("BDG 86 Marmi" - CTS Europe). First, it was preferred to implement “humid” methodologies aimed at removing surface substances precisely because of the complexity of the situation and the porosity of the substrate. This would avoid spreading the substance to infect the internal areas of the sculpture. The restorer chose to adopt laser technology, not available in the 2005 restoration intervention. If properly calibrated, this method allows removing the deposits without the diffusion of the substances. The only exception in this phase was made for tests with Agar gel, alone or interposed to the laser beam, thanks to the little free water released in the interface with the marble. Despite this, even the use of Agar has not proved satisfactory since it leaves a slight halo of "wetting" of the yellowish part of the dirt, even after drying. Before proceeding with the intervention, analytical studies were carried out to exclude the presence of possible polychromies (in particular in the form of laccases) in the residues present in some recesses of the folds of the garment. The results excluded the aforementioned hypothesis. The laser devices adopted were all Nd-YAG sources, almost all with wavelength = 1064nm: the Compact Phoenix - Lynton (Q-Switch mode), the EOS Combo-Light for Art (LQS and Free Running mode ), the Thunder Art-Light for Art (Q-Switch mode), the Laser Blaster - Light for Art (LQS mode). In particular, with Thunder Art, the surface was irradiated even at a wavelength of 532 nm, to try to degrade and ablate the organic substance. With the Laser Blaster, we aimed at a sterilizing side effect of the possible biodeteriogens still present (fungal and algal spores, bacteria).
 
The cavity originally envisaged for the reception of the original head and neck was irradiated with the laser only on the most external and visible circular section, since we tried to keep as much as possible the material traces of any ancient adhesives or bedding. The successive passages with the different lasers have given good results to the naked eye, improving the situation to a level that was considered more than acceptable by the construction management.

At this point, having removed most of the superimposed substance, the path of a further step of chemical cleaning was again viable, given that most of the superficially polluting substances had been removed, sterilized and probably many metallic compounds even partially reduced in the laser cleaning phase, and the risk of diffusion and reactions inside the marble was consequently lowered. Furthermore, questions remained open regarding the phenomenon that had occurred after the 2005 restoration and some tests had to be done to try to understand what had happened. In this way, we would try to avoid the repetition of the same dynamic, rather than biological colonization, oxidation, or reoxidation (even spontaneous with air humidity) of the residual metal compounds.
 
Small, specific tests were therefore carried out on the less visible parts of the sculpture with the intent, if an effective methodology had been developed as a visible result, to monitor the stability in the behavior of the tests during a future period defined based on colorimetric measurements of the starting state. In this way, with the indispensable guarantees of effectiveness, control of immediate and future reactions, it will be possible in the future to dose and extend the methodology eventually tested to other areas of the sculpture, further improving its visibility. A series of tests were therefore carried out, mainly involving two cross-strategies: action on manganese and action on iron. For the manganese, it was chosen to continue with tests using a compound based on hydrazine monohydrate and hydroxylammonium chloride at Ph=7 which had already been applied locally with effective immediate results in the 2005 restoration.  
 
Appropriate precautions were undertaken for the iron components of the sculpture. The selected substances, N-acetyl-L-cysteine and L-cysteine hydrochloride with suitably buffered pH with "Trizma base" buffer (in comparison) have a chelating effect also on manganese (in second-order if iron is also co-present). The tests performed gave very evident lightning results, with the BDG very (too) showy and in general stronger and more uniform than the results obtained with cysteine. Both systems also acted on the other metal compared to that for which they were targeted, the BDG on iron compounds and cysteine on those with manganese. In addition, BDG dilution tests have been carried out to graduate from such disruptive effects. At the end of the cleaning tests, the test surfaces still needed to be treated with measures aimed at lowering the possibility of re-oxidation in the future of residual metal ions with indirect, shielding, and direct blocking systems with the addition of anti-oxidant substance. The first system consists of the application of a polymer that acts as a barrier to the humidity of the air, to which an anti-UV filter is hooked to avoid the arrival of activation energies of possible reactions through ultraviolet rays. The second system attempted in the trial was to apply to the surface already treated as an antioxidant agent of reduced iron and manganese.

At the end of the restoration, a campaign of colorimetric readings was conducted to monitor the evolution over time of the chemical tests compared with the readings taken on the surfaces not chemically treated (but only with the application of the laser).
Monitoring and measurements become even more important as the work is predictably subjected to significant climatic and environmental changes, with the sculpture being exhibited in the work of a traveling exhibition (Patrons) in the United States in a year. The results of the tests will be useful to decide on a further degree of calibrated cleaning to be carried out in the future on the artifact, as well as the effectiveness of a methodology that can be extended to similar cases. From a structural point of view, the work does not present particularly serious problems beyond the dissolution of the surfaces of the drapery. Interestingly, the work of the artist around the base of the sculpture is unfinished. This part of the sculpture was carved using a pointed tip of different inclinations, a flat-cut scalprum, gradina, and drill. The use of a rasp appears widespread on most of the surfaces of the slopes of the drapery.

The large cavity on the sculpture between the shoulders without holes for connecting pins functioned as the insertion point for the head. Considering how the base and seat for the neck are designed so that the statue appears that it is leaning forward, as well as the deformation of its limbs from the perspective from a lowered point of view, the hypothesis is that the statue was located in an elevated position. The question remains as to how the statue was secured as there are no holes or brackets in the base. We note a curious angle and cut of the marble on the back region of the statue, perhaps because the original block of marble was already faceted irregularly. Deepening the folds on the back of the sculpture too intensely would correspond to excessive exhaustion of the solid section near the feet and therefore a present great risk to the sculpture. The work done on the back of the sculpture shows that the artist’s initial subdivision of zones with relief was first realized in a flat perspective and then deepened in some areas (such as the folds), while in other areas it remained flat.   

The presence of a series of small stumps of iron pins remains under consideration. These pins are inserted in relative holes curiously grouped on the right side of the figure at the hip, perhaps to be put in relation to another larger hole, also with iron oxides, executed near the patella of the right knee (this last hole seems functional but devoid of corresponding marks on the base).  It is to be excluded that the pins functioned to attach additions of marble to the original statue, given that they are not located in correspondence with the “saddle” seats placed on the crests of the folds and missing lost restoration pieces. Rather, these pins are located randomly in the grooves between the folds. This particular position has suggested (according to Dr. C. Valeri) that two metal plates (of a copper allow) ertr inserted in the two depressions involved, which from a distance could give the sensation of atmospheric movement through a luminous flickering effect.