the role of the italian central institute of restoration in the field of underwater archaeology

The International Journal of Nautical Archaeology (2002) 31.1: 74–82doi:10.1006/ijna.2002.1004

The role of the Italian Central Institute of Restoration in thefield of underwater archaeology

Roberto PetriaggiUnderwater Archaeological Operation Unit, Istituto Centrale per il Restauro, 9 P.zza S. Francesco di Paola,00184 Rome, Italy

In 1987, given the importance and complexity of the correct recovery and conservation procedures for underwaterarchaeological finds, an Underwater Archaeological Operations Unit was set up within the Italian Central Institute forRestoration. This Unit is made up of archaeologists, conservators, biologists and chemists, all of whom are underwater experts.It provides consultancy services and scientific and technical assistance for problems relating to the recovery, conservation,protection, and restoration of underwater archaeological heritage at the request of the Archaeological Superintendents. Greatattention is paid to the professional training of underwater conservators. Specialized courses in the conservation of materialsof underwater provenance are organized as part of its programme. This paper illustrates some of the main initiatives both inthe restoration of archaeological objects and in training, in which the Institute has been involved, since the Underwater Unitwas created. � 2002 The Nautical Archaeology Society

Key words: conservation, underwater archaeology, submerged structures, in-situ protection, bronze restoration.

Introduction

I t is now generally recognized that the plan-ning of an underwater archaeological excava-tion must take into careful consideration the

phases of emergency conservation treatment onfinds that will have deteriorated in varying degreesduring their long exposure to water. In fact, thelack of preventative treatment against the corro-sion and deterioration processes that take place assoon as a submerged artefact has been recoveredinvariably result in its complete loss and makefurther research impossible (Petriaggi, 2001).Therefore, emergency conservation treatmentmust be carried out before storage of the salvagedobjects and prior to their analysis. It would evenbe advisable to have, present alongside under-water archaeologists, conservators who arecapable of deciding upon specific treatments fromthe very moment that artefacts are identified onthe seabed. It is not uncommon for highlydegraded or organic finds to suffer irreversibledamage at the moment of recovery, or bedestroyed as a result of being handled incorrectly(Meucci, 1991). The amount of attention thatmust be paid to conservation operations is not an

1057–2414/02/010074+09 $35.00/0

optional decision but is vital for the preservationof the discovered heritage (Petriaggi, 1997).Careful conservation procedures do not of courseexclude the necessary graphic and photographicdocumentation and filming of each object as itappeared at the time of its discovery. Similarattention must be paid to the area surroundingthe object to be recovered: recording the condi-tions in which it is lying and taking samples fromthe seabed and from the water itself. The environ-mental conditions directly affect the deteriorationprocesses of both organic and inorganic archaeo-logical material with different consequences.

Therefore, given the importance and complex-ity of correct recovery procedures and the con-servation of underwater archaeological finds,the Underwater Archaeological Operations Unitwas set up within the Italian Central Institutefor Restoration in 1997. This Unit, made up ofarchaeologists, conservators, biologists, andchemists, all of whom are underwater experts,provides consultancy services and scientific andtechnical assistance for problems relating tothe recovery, conservation, protection, andrestoration of the underwater archaeologicalheritage at the request of the Archaeological

� 2002 The Nautical Archaeology Society

R. PETRIAGGI: I.C.R. IN UNDERWATER ARCHAEOLOGY

Superintendents. Great attention is paid to theprofessional training of underwater restorers. Infact, specialized courses are organized in the con-servation of materials of underwater provenanceas part of the activities of the Institute’s School ofRestoration. These courses are open not only tostudents of the Institute but also to restorerswithin the Superintendences, should they requestthem. This paper illustrates some of the maininitiatives in which the Institute has beeninvolved, both in the restoration of archaeologicalobjects and in training, since the Underwater Unitwas created.

Figure 1. The Satyr of Mazara del Vallo. (Photo: I.C.R.)

Figure 2. The satyr on the chalcedonic agate Cameo attrib-uted to Sostratus (Photo: Luciano Pedicini).

Restoration of archaeological objectsIn the spring of 1998, a bronze statue was discov-ered on the sea floor in the Sicily Channel, close tothe city of Mazara del Vallo, at a depth of about500 m. It represents a satyr, a demon who formedpart of the orgiastic cortege that accompaniedDionysus, the Greek god of wine (Fig. 1). The

work may be an original of the Hellenistic Period,dating between the end of the 4th and the early3rd century BC, or a later reproduction madebetween the 2nd and the end of the 1st centuryBC. It is known, above all from the Romanconquest of Greece and thus from the second halfof the 2nd century BC, that a growing trade inworks of art had developed to satisfy the demandsof the cultured Roman aristocracy. Only marblecopies by Roman sculptors remain of the manyoriginal bronze statues that have largely dis-appeared. A few originals, as is well known,survived and reappeared in the present day thanksto underwater archaeological discoveries. Notableexamples are: the bronzes from the wreck ofMadhia in Tunisia; those of Antikythira; the Zeusof Cape Artemisium at the National Museum ofAthens; and the Bronzes of Riace. The Satyr ofMazara, which is larger than life-size, is perhaps,as suggested by Professor Paolo Moreno, theprototype that inspired artists of the AugustanAge. One example is the carver of the chalcedonicagate cameo (Fig. 2), attributed to Sostratus,dating from the end of the 1st century BC—beginning of the 1st century AD and now inthe Archaeological Museum of Naples. Othersare the sculptors of bas-reliefs, particularly of

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Figure 3. The special mobile support constructed with ametal frame made of two coupled half-cylinders to facilitatethe movement of the statue during treatment. (Photo:I.C.R.)

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Figure 4. The satyr and its separated leg at the start of testsmeasuring the corrosion speed. (Photo: I.C.R.)

sarcophagus fronts, dating from the 2nd centuryAD. The mythological creature is captured in amoment of orgiastic dance, about to leap on to hisright foot with his left leg raised, his torso rotatedand arms extended. His head is hanging backalmost touching his shoulders, letting his hair flyin the wind in flowing locks, invigorated by divineintoxication. A panther skin was probably foldedover his left arm with an empty wine goblethanging from his hand. His right hand was shak-ing the thyrsus, the long staff tipped with anornament like a pine cone, adorned with ribbons,and carried by Dionysos and his followers. It isdifficult, in its present state, to establish whetherthe find was part of a more complex group ofstatues or an individual figure.

In October 1998, the statue was transported toour laboratories in Rome in order to undergoconservation. The treatment operations wereplanned according to a precise working schedule,based on the experience acquired by the Institutein restoring ancient bronze statues over the past30 years. The most famous of these includethe Selinunte Ephebus, the Bronzes of Riace, andthe equestrian statue of Marcus Aurelius on theCapitoline Hill in Rome.

As the standing leg and the original base of thestatue were missing, a special mobile support wasconstructed with a metal frame made of twocoupled half-cylinders to facilitate moving it dur-ing treatment (Fig. 3). These encase the Satyr,which, rotating on its own axis, can be moved tothe position required. On reaching the desiredposition, one of the two elements is easily dis-mantled, and the work proceeds, thereby avoiding

any kind of shock that might result from themovements and changes in position involved in aconservation operation. Passing on to the docu-mentation phase, the first step was to make aphotogrammetric survey; then, a laser probe wasused to produce a three-dimensional image of thestatue. The images obtained have been used as agraphic base, both for the documentation of allthe operational phases and for planning the sup-port devices for museum exhibition as well as forcarrying out the study for joining the leg to thebody of the statue (Fig. 4). The graphic documen-tation was supported from the very beginning byphotographs and video film. There followed thefirst diagnostic tests to determine the nature andthickness of the incrustations and patinas, and toexamine the condition of the metal core and,therefore, the extent of surface corrosion. Testsmeasuring the corrosion speed as well as chemicaland metallographic tests were carried out forthe qualitative and quantitative analysis of thecomposition of the alloy and patinas.


Figure 5. Metallographic analysis showing the presence ofslip planes in the zone of the head of the satyr. (Photo:I.C.R.)

On arrival at the laboratory, the surfaces of theartefact appeared to be covered with thick incrus-tations caused by the physico-chemical conditionsof the milieu in which it had been embedded.There were numerous traces of benthonitic marineorganisms, madrepores, molluscs, bivalves, andaquatic worms belonging to the Polychaete classwith calcareous exoskeletons, whereas fromstudies made at the moment of recovery, theabsence of phytobenthos (aquatic algae andplants) was evident, a factor that confirms thegreat depth at which the find lay. The action ofsulphate-reducing bacteria was assumed to beresponsible for the zones covered with a blackpatina, but this was not confirmed by the X-raydiffraction (XRD) analysis. However, traces ofsulphates deriving from the metabolism of thesebacteria were identified using microchemical tests.

The XRD analysis of the patinas, incrustations,and sediment made it possible to identify thevarious components that consist mainly of cal-cium carbonate (calcite and aragonite) as well asfeldspar and pyroxene in the sediment, and leadcarbonate (cerussite), lead sulphate (anglesite),and cupric oxychloride (paratacamite) that areproducts of lead and copper corrosion. The elec-trochemical corrosion speed was measured, on awet surface, using the polarization resistancemethod, and the incrustations and patinas weremeasured using Eddy currents. A wide range ofcorrosion speed values were recorded, varyingfrom a few microns to over 2000 microns per year,depending on the type of surface: low values forthe incrustations and very high values in zoneswhere a marked presence of cupric oxychloridewas evident. Measurements will be resumed whenthe cleaning phase is completed to check thepossible influence of the incrustations on thevariability of the data. From the results obtainedso far, it would appear inadvisable to subject theSatyr to any further washing processes, owing tothe high degree of mineralization displayed in themetal. It does instead seem necessary to completethe conservation phase, as well as to repeat thecorrosion speed measurements, extract solublesalts from the zones not at risk and carry outgeneral treatment to inhibit corrosion, decidingafter a further evaluation whether or not to pro-ceed with stabilizing treatment using acrylic resinsand microcrystalline waxes.

In order to better characterize the work, withregard to both the chemical composition of thealloy and its corrosion products, and to be able toidentify the structural characteristics regarding

the method of casting, chemical and metallo-graphic analysis and X-ray and endoscopic exami-nations were carried out. The analytical methodused to determine the components of the alloy,qualitatively and quantitatively, was energy dis-persive X-ray fluorescence applied on samplestaken from three different zones of the statue. Thefirst three samples also underwent a metallo-graphic study, from which it was possible torecognize the type and extent of corrosion, crack-ing, shrinkage cavities, and inclusions. The pres-ence of slip planes that became evident afterchemical treatment with ferric chloride wouldindicate that the statue had been thermally andmechanically worked, particularly in the zone ofthe head, where these planes are more widespread(Fig. 5).

The result of energy dispersive X-ray fluor-escence studies shows considerable variability inthe lead content within the alloy; the mean per-centage of this metal is, however, quite highand stands at around 16–17%, a level that isoften found in artefacts from the Roman Period.Moreover, with regard to the lead present, isotopeanalysis will shortly be carried out in the hope ofacquiring information as to the provenance of theoriginal ore. No traces of the casting clay havesurvived within the statue, and this reduces thehope of establishing a more precise date for thestatue through thermoluminescence analysis.

The statue, weighing 108 kg (the body weighs96 kg, and the detached leg 12 kg), with an aver-age metal wall thickness of around 6–7 mm, willbe supported by a steel structure (Fig. 6), consist-ing of a vertical bar connected to a ball-and-socket joint base that will be fixed inside the torso.

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The shoulders will be supported by a highercrossbar, while four smaller splayed bars, on eachside of the vertical, will support the sides of thestatue. A diagonal bar, to suspend the remainingleg, will complete the system. The weight of thewhole statue resting on the base will be about140 kg. An anti-seismic base is currently in itsplanning phase. Its construction has been spon-sored by the Europa Metalli Company, a worldleader in the manufacture of copper and relatedalloys. Moreover, following restoration treat-ment, it will be necessary to protect the statuefrom humidity that would trigger new processesof corrosion. Therefore, it will have to be enclosedwithin a glass display cabinet that fully insulates itfrom the external environment. Furthermore, oncompletion of the restoration, documentation ofthe work carried out will be copied on to aCD-ROM, so that everyone may experience thestages that led to the discovery and final recovery

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of this irreplaceable example of the art andtechnology of Classical Antiquity.

Figure 6. The steel structure that will be fixed inside the body of the satyr to support it. (Photo: I.C.R.)

Training coursesConcerning training courses for underwaterrestorers, the following are examples of recentactivities: the academic years 1998–1999 and1999–2000 saw the organization of two specializedcourses in conservation and restoration ofmaterial of underwater provenance, reserved forrestorers who already hold diplomas from theInstitute or are employed as restorers by theMinistry for Cultural Heritage and CulturalActivities. The courses consisted of 3 months oflessons on subjects concerning underwater archae-ology, conservation, chemistry, marine biologyand diagnostic tests; 1 month of practical work onsite; and 1 month in the laboratory. The aim of


Figure 7. Torre Santa Sabina: a phase of the emergencyrecovery intervention carried out during the underwaterwork. (Photo: I.C.R.)

Figure 8. Torre Santa Sabina. Four helmets stacked, oneon top of the other at the moment of the shipwreck,photographed during the conservation (Photo: I.C.R.)

the first course during the years 1998–1999 wasthe conservation of metal items of underwaterprovenance, with particular emphasis on iron.

The first practical work-site was set up at TorreSanta Sabina in Puglia in the south of Italy(D’Andria, 1976; Coppola, 1977; Siebert, 1977;Cocchiaro, 1994, Taras XIV, 1, 183 tav. XCII;1995, Taras XV, 1, 143; Pietropaolo, 1997),where the Institute collaborated with the localArchaeological Superintendent. Emergency con-servation treatment was carried out in a labora-tory set up in the vicinity of the work-site (Fig. 7),while the conservation work was completed by thestudents later, during their apprenticeship at ourRome laboratories. During the archaeologicalsurvey, a metal detector was used, which made itrelatively easy to locate the areas where metalremains were present. The archaeological excava-tion was intentionally restricted to an area of10�10 m out of a total surface area that hadbeen visually and electronically explored by metaldetector and comprized about 900 m sq. This

restriction obviated our being put in the positionof lifting too large a quantity of material torecover and conserve correctly within the timeand with the facilities available. This choiceproved a correct one, as, during the course ofoperations, hundreds of pieces were found, mostof them metal, even though there were also pot-sherds of the Greek and Roman periods andstructural components of a later wreck, which,from the association of a number of helmets andiron nails, could be dated to between the 16th and17th century. Seven helmets were recovered; fourof these had been stacked, one on top of the other,at the moment of the shipwreck and, given theprecarious state of the metal, have not beenseparated (Fig. 8). It was decided to restore themas they were found, and as they had been placedin the ship’s arsenal (Fig. 9). Below the fourstacked helmets were the fragmentary remains ofa boat, its planks joined together with oxidizediron nails, the heads of which were covered with

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Figure 9. Torre Santa Sabina. Four helmets stacked, one ontop of the other, after conservation. (Photo: I.C.R.)

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Figure 10. Punta Ala. A general view of the cast of thewreck. (Photo: I.C.R.)

Figure 11. Torre Astura. Cleaning test on a submerged wallof a Roman vivarium. (Photo: I.C.R.)

ncrusted pebbles and sand. The other threeelmets were scattered around, under a layer of0–40 cm of sand and pebbles. The whole sur-ounding seabed was covered with iron nails thatere unrecognizable owing to their incrustations,hile a fragment of bulkhead frame or floor

imber, perhaps belonging to the same wreck, laypart from the few plank remains.The shallow depth (about 2 m) and the extreme

roximity to the water’s edge suggest that theseemains were transported almost to the shore byenturies of tides and that the ship had broken uparther out to sea, on the rocks at the entrance tohe bay, the victim of a violent storm. An alterna-ive theory is that it may have been sunk duringne of the many battles that took place along thistretch of coastline.

An iron cannon ball was in fact discovered notar from the trial sample excavation, and inrevious years, various kinds of arms have beenound in the Gulf. The conservation of the ironelmets, which date between the 16th and 17thentury, has been completed. They will soon beanded over to the Museum of Brindisi, thelosest city to the zone in which they were located,n order to be exhibited to the public.

The second training course, concerning theonservation in situ of ancient wrecks and siliconeubber casting techniques, took place during theears 1999–2000. A site for this specialist workas chosen on the coast of Tuscany near Puntala (Cygielman & De Tommaso, 1998; Gambogi

t al., in press). The subject of study was a wreckf the Modern Era, probably dating from the 19thentury. Before preparing the silicone mould, thetudents surveyed and photographed the wrecknd took several samples of the seabed sediment

and planking to identify their origin. To make themould, the silicone was spread on panels ofsynthetic tissue (fibreglass) that were then placed,one by one, on the surface of the wreck, until theyformed a compact layer. A stiffening metal frame-work was then glued on to this with epoxy resin,to avoid any distortion during the construction ofthe mould (Fig. 10). The object of this experimentwas to test new methods to reproduce parts of thesubmerged wreck, for both research and museo-graphical purposes. The construction of a castfrom the mould of a wreck or part of one,depending on its dimensions and the relativeobstacles involved, would in fact make it possibleto create resource museums of considerable publicinterest and of undoubted use to students, ata practically insignificant cost, bearing in mindthat expensive air-conditioning systems are notrequired for resin reproductions.

It must also be noted that a partial cast couldbe completed in a later phase, depending on the


availability of funding and the necessary staff tocontinue the excavation. In the meantime, a wreckmay be left on the sea floor, protected by the samesilicone mould as that used for the casts (Meucci,1986; Petriaggi, 2001).

The emergency treatment laboratory on land,co-ordinated by the restorers from the Instituteand Superintendence, carried out the emergencytreatment operations. It participated in planningthe recovery operations, compiling card inventoryfiles, washing the recovered materials, and pack-ing and transporting them to our Rome Centre.

Projects for the future foresee the continuationof this commitment, in both the training and

experimental research sectors. During the summerof 2001, for instance, conservation site-workinvolved submerged structures that form part of aRoman villa with vivaria for fish farming, namelythe Villa of Torre Astura, 70 km south of Rome(Piccarreta, 1977). In the future, an attempt willbe made to consolidate the villa’s aqueduct,which, eroded by the waves, is on the verge ofcollapse. For the present, cleaning and consolida-tion techniques have been successfully tested onthe submerged walls of the vivaria. Various tools,lancets, and sponges have been employed forcleaning operations on biological encrustation(Fig. 11), and the structure of the walls has beenreinforced by using a mortar especially created forunderwater intervention on submerged structures,frescoes, and mosaics (Figs 12 & 13).

For this purpose, the Archaeological Super-intendence of Naples has requested the collabor-ation of the Central Institute of Restoration in thestudy of appropriate conservation and restorationmethods for the submerged structures of theancient Roman city of Baia (Scognamiglio, 1997),the first Italian underwater archaeological parkopen to the public (Fig. 14). This will be a realchallenge for the coming years and a chance todevelop our research. The site of Baia could be thebest site for training a great number of youngunderwater conservators.

Figures 12–13. The underwater conservator is reinforcingthe structure of the walls by using a mortar created especiallyfor underwater intervention on submerged structures.(Photo: I.C.R.)

Figure 14. Baia. A view of a pila (pier) of the harbour.(Photo: I.C.R.)

ReferencesCocchiaro, A., 1994, Carovigno (Brindisi), Torre Santa Sabina. Soprintendenza Archeologica della Puglia Notiziario delle

attivita di tutela giugno 1992–dicembre 1993, Taras XIV. 1.Cocchiaro, A., 1995, Carovigno (Brindisi), Torre Santa Sabina. Soprintendenza Archeologica della Puglia Notiziario delle

attivita di tutela gennaio–dicembre 1994, Taras XV. 1.Coppola, D., 1977, Civilta antiche nel territorio di Torre Santa Sabina (Carovigno Brindisi): ricostruzione topografica e

avvicendamenti culturali. Ricerche e Studi Brindisini, X: 47–110.

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Cygielman, M. & De Tommaso G., 1998, Castiglione della Pescaia—Punta Ala. In G. Poggesi & P. Rendini (Eds), MemorieSommerse, Archeologia Subacquea in Toscana, 91–123. Pitigliano.

D’Andria, F., 1976, Le ceramiche arcaiche di Torre Santa Sabina e gli approdi adriatici della Messapia. Ricerche e StudiBrindisini, IX: 19–66.

Gambogi, P., Bargagliotti, S. & Cibecchini, F., in press, Il relitto B di Punta Ala—Cala Del Barbiere. La campagna1998—Risultati preliminari. Archeologia Subacquea, Studi, Ricerche e Documenti, III.

Meucci, C., 1986, Le bateau arabo-normand de Marsala: la protection in situ. In ICCROM (Ed.), Preventive Measures DuringExcavation and Site Protection, 155–158. Rome.

Meucci, C., 1991, Relitti subacquei e conservazione, dallo scavo al progetto di restauro. In A. Nardini (Ed.), Archeologia,Recupero e Conservazione, 51–73. Florence.

Petriaggi, R., 1997, Il Museo delle Navi di Fiumicino: problemi di conservazione e restauro. I Beni Culturali, 6: 15–18.Petriaggi, R., 2001, Recupero, o quali altre scelte nel caso dei relitti antichi?, Forma Maris, Forum Internazionale di Archeologia

subacquea, 149–152. Naples.Piccarreta, F., 1977, Astura. Forma Italiae (R I,13). Firenze.Pietropaolo, L., 1997, L’approdo di Torre S. Sabina (Brindisi). Le ceramiche comuni di eta romana. Aspetti tipologici,

tecnologici e distributivi. Atti del convegno nazionale di Archeologia Subacquea, Anzio, 30–31 maggio 1996, 249–270. Bari.Scognamiglio, E., 1997, Aggiornamenti per la topografia di Baia sommersa. Archeologia Subacquea. Studi, ricerche e documenti,

II: 35–45, Roma.Siebert, G., 1977, Bols a reliefs d’ateliers grecs dans le depot marin de Santa Sabina en Apulie. Ricerche e Studi Brindisini, X:

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the role of the italian central institute of restoration in the field of underwater archaeology

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