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I Bronzi di Riace. Restauro come conoscenza
Anno: 2003
a cura di: AA.VV.
Contenuti:
Artemide Editore, 2003, formato 27x21, cofanetto con due volumi e portfolio (volume primo a cura di Alessandra Melucco Vaccaro e Giovanna de Palma, Archeologia, Restauro, Conservazione: 269 pagine, illustrazioni a colori e in b/n; volume secondo Mario Micheli, Massimo Vidale, Scavo all’interno delle due statue: 214 pagine, illustrazioni a colori e in b/n; portfolio Mario Micheli, Massimo Vidale, Nove tavole delle due statue: 9 tavole estraibili, formato 50x70), € 100.00 ISBN 88-86291-73-6
ABSTRACT
Il volume presenta il resoconto del restauro totale delle due statue del Museo Nazionale di Reggio Calabria portato avanti a cura dell’Istituto Centrale per il Restauro. Raccoglie i contributi di storici dell’arte, archeologi, chimici e fisici, sui vari aspetti del restauro e sui confronti con altre opere d’arte sottoposte a operazioni analoghe.
This volume presents the results of the project of conservation carried out by ICR, in collaboration with the Archaeological Superintendency of Calabria and FINMECCANICA S.p.A, on the two Riace Bronzes. The project started because, after videoprobe inspections the two statues turned out to be severely attacked on the interior walls by corrosion processes. Corrosion was enhanced by the joint effects of cycles of moisture variations in the exhibition environment and the permanence in the interior cavities of substantial amounts of the original casting cores soaked with salts and chemical residues from previous conservation treatments. Actually, although the published reports stated that the two statues had been completely cleaned of the interior materials, it was found that both retained substantial amounts of the original casting cores, particularly in the legs and in the arms (at the end of our work, we would have removed from both the statues more than 120 kg of casting core). Originally, basing ourselves upon the information available after the restoration carried out in Florence, including detailed archeometric information, we assumed that the casting cores had been poured into the wax cavities in liquid or semi-liquid form, according to the well-known indirect lost-wax casting technology. Thus our first effort was the invention of a remotedly-controlled mechanical arm, provided with vibrating scalpels powered with forced air and video-probe terminals for demolishing the inner clay contents. But as soon as we started our work in the interior of the right leg of Statue B, we found that the clay residues detached from the inner walls were in fact delicate and complex multi-layered structures. At this point, we felt that the inner casting cores were in fact more complex than previously expected: given the rarity of similar context, we decided that the inner stratigraphic structure of the clay casting cores of statue B and A had to be carefully documented and possibly preserved outside their cavities. Thus we abandoned the remotely controlled mechanical arm and adopted lighter excavation tools (mainly ultrasonic cleaners used without cooling hydraulic system) directly operated by the hands of the conservators and archaeologist involved in the project. In devicing this new excavation technology, we got inspired by contemporary video-probe technology applied in non-invasive micro-surgery. We started excavating the right leg of Riace B from the plant of the foot, enlarging the pre-existing access in the remnants of the lead pivot, and moved inward. We recorded a “tomographic” cross-section of the stratigraphy of the casting core at intervals of 5 cm, and, whenever needed, at closer intervals. We recorded patterns of variable complexity suggesting a concentric slab-construction technique around the inner iron rods of the kanabos. Such concentric layers were also encountered in the left leg of Statue B, in its torso, and, perhaps not always so clearly, in the casting core of Statue A. In both cases, we found and recorded regular grooves and fingerprints showing that the clay had been applied by the craftpersons pressing and shaping the materials from outside, according to the techniques normally associated to the direct lost-wax casting process. Besides photographing and drawing the cross- sections, we also recorded about 80 hours of tapes that document the development of our work and the inner contexts before their disturbance. In many instances, the concentric pieces we found were extracted and carefully refitted together, so that large lumps of the original casting cores are presently available for inspection (this collection is still at the ICR in Rome, but we are currently planning to give it back to the Reggio Calabria Museum). The most complex structures were encountered (in both statues) at the interface or joint between the uppermost preserved fill of the tights and the torso: here, a series of cylinder-like holes, partially cutting one another, had been re-filled with peculiar vertical clay strips or coils, having a subtriangular section and swallow tail-like lower surface for a better fitting with other coils. The purpose of these pre-formed coils (whose presence was totally unexpected) is a difficult question: we think that they represent a good technical response to the problem of filling in the most precise fashion vertical cylinder-like cavities cut into the filling of the legs while assembling the torso to the legs in several trials. This hypothesis obviously assumes that legs and torso were in fact constructed and shaped as separated pieces, and later assembled and covered with wax panels. Other important data were gathered in the armpits of both statues and in the right arm of Statue B. The careful inspection of the inner armpits and the base of the neck of Statue A showed the presence of a distinctive clay colored in yellow and red that was evidently used for soldering the arms and the head to the rest of the figure. This clay, both from a mineralogical (petrographic) and chemical viewpoint, is completely different from that used for the casting core. We are left with two possible solutions: the bronzesmiths assembled these parts in a location different from that of the original casting, or they used for soldering a quite different clay, may be for its supposed properties, collected from another place. In the right arm Statue B we found another type of clay, most probably inserted into the wax model from outside (i.e. using, this time, an indirect lost-wax process). This evidence confirmed that the right arm of Statue B is a later transformation, most probably carried out in a location quite distant from the original casting place. On the whole, this evidence supports the view that Statue B underwent in the Roman period an extensive alteration, probably meant to make it more similar to the prestigious and “heroic” features of the younger warrior portrayed in Statue A. By putting together all the sections (about 80 for the two statues) and the other technical details ascertained with our excavation, we provided hypothetical reconstructions of the clay models probably prepared by the bronzesmiths before applying the wax. Significantly, Statue B, dated by most art historians around 430 BC, i.e. to a moment already influenced by the example of Polycletus, shows a more careful anatomical modelling in the clay itself, while Statue A is simpler, and its modelling seems to have been accomplished to a greater extent in the wax covering. The report provides exhaustive (we hope) information on the excavation, the tools we invented and tested, on the structure of the casting cores, and a discussion of the difficult question of the indirect or direct casting process followed by the Greek craftpersons. Presently, we feel that great part of the scientific community, on the wave of the excellent standards and great authority of the restoration work performed in the seventies in Florence, has accepted too hurriedly the theory of the indirect lost-wax technique. On the whole, we consider the direct hypothesis much more likely than the indirect hypothesis, but our data - made available to the criticism of our collegues - are open to discussion. The report also provides the information we gathered with a new radiographic campaigns, and a consequent new archeo-metallurgical survey of the two masterpieces.
INDICI
Volume primo: Archeologia, Restauro, Conservazione
a cura di Alessandra Melucco Vaccaro, Giovanna De Palma
Almamaria Mignosi Tantillo, Prefazione
Giovanna De Palma, Introduzione
Parte prima: Relazioni introduttive
Sabatino Moscati, Giovanni Di Sorte, Mario Serio, Elena Lattanzi, Roberto Spadea, Antonino Di Vita, Alessandra Melucco Vaccaro, Mario Torelli
Parte seconda: Archeologia dei grandi Bronzi
P. Moreno, Argo e Riace
Ch. Piteros, Una statua di bronzo da Argo
E. Formigli, I Bronzi di Riace sono stati costruiti con la tecnica diretta della cera persa?
M.L. Lazzarini, Rendiconti di spesa per l’esecuzione di statue di bronzo
E. Tulupa, Ricordo di C. Chatziliou, restauratore del Kouros del Pireo
A. Oddy, I. McIntyre, The conservation of a hellenistic life-size bronze in the British Museum
G. Prisco, P. Fiorentino, Prime considerazioni sulla testa da Basilea alla luce dell’intervento di restauro
G. De Palma, P. Fiorentino, I bronzi di Brindisi
P. Moreno, Statua in bronzo di Emilio Paolo
Parte terza: Il contributo delle tecnologie avanzate e dell’archeometria
G. Lombardi, P. L. Bianchetti, M. Vidale, Le terre di fusione dei Bronzi di Riace
A. Fiorentino, Nannofossili calcarei nelle terre di fusione dei Bronzi di Riace
G. Schneider, E. Formigli, Hypotheses on the Provenance of the Riace Bronzes from Studies of their Core Materials
E. Mello, Studio metallografico, analitico, microanalitico e mediante tecniche spettroscopiche di analisi delle superfici di due campioni prelevati dalle statue di Riace
M. Bartolini , R. Cigna , B. Colombo, G. D’Ercoli, M. Marabelli, A. Marano, Misure di microcondensazione capillare e controlli elettrochimici per il restauro dei Bronzi di Riace
F. Zucchi, V. Grassi, G. Trabanelli, Prove preliminari di inibizione della corrosione del rame con benzotriazolo
A. Corsanego, S. D’Agostino, I dispositivi di protezione antisismica dei Bronzi di Riace: metodo ed obiettivi
C. Mazzieri, S. Pastorino, Sperimentazione ed attuazione dei supporti antisismici
A. Giovagnoli, M. Marabelli, S. Barcellona, Misure di inquinamento atmosferico nel Museo Archeologico di Reggio Calabria per la salvaguardia dei Bronzi di Riace
D.M. Fontana, Impianto di condizionamento per la sala di esposizione dei Bronzi di Riace
Commenti e contributi alla discussione
S. Angelucci, C. Rolley, W.D. Heilmeyer, N. Beloyannis
Bibliografia
Volume secondo: Scavo dell’interno delle due statue
di Mario Micheli, Massimo Vidale
Introduzione
La scoperta degli interni delle statue bronzee
Altre esperienze di esplorazione interna di statue bronzee presso l’ICR
I due bronzi di Riace: storia degli interventi precedenti
Il controllo dello stato di conservazione dei Bronzi eseguito tra il 1984 e il 1986
Storia del progetto di scavo degli interni delle due statue di Riace. Dalla realizzazione di un telemanipolatore a controllo remoto alla scoperta di complesse stratificazioni nella terra di fusione
Natura del contesto archeologico indagato. Elementi di modellato, strati, interfacce positive e negative, riempimenti (sia di materiale plastico sia incoerente), cercini con incasso posteriore a coda di rondine ed elementi preformati con altre sezioni; Passaggio a tecniche di scavo e rilievo di tipo essenzialmente archeologico, basate sul controllo manuale degli strumenti
Organizzazione e struttura del laboratorio. Metodi, problemi operativi, soluzioni tecniche e strumenti dello scavo interno
La documentazione. Unità di prelievo e loro archiviazione. Planimetrie e sezioni, e relativi metodi di rilievo filmati, fotografie digitali, diario di scavo e banca dati informatica. Altri archivi
Osservazioni generali sulle due statue prima dell’intervento
La statua B
La statua A
Le ipotesi correnti sulle tecniche di fusione dei grandi bronzi classici e le loro implicazioni archeometriche ed archeologiche
Bronzi di Riace: metodo diretto o indiretto?
Replicazione sperimentale dei processi di costruzione del modello interno per la fusione di una gamba
Ricostruzione finale delle tecniche di manifattura del nucleo terroso interno delle due statue, secondo l’ipotesi del metodo diretto
Altre riflessioni metodologiche
Summary
Portfolio: Nove tavole delle due statue
a cura di Mario Micheli, Massimo Vidale