12th International Congress on the Deterioration and Conservation of Stone Columbia University, New York, 2012 ALTERATION PATTERNS OF MARBLE UNDER DIFFERENT ENVIRONMENTAL EXPOSURES: A SYSTEMATIC APPROACH FROM THE STAGLIENO MONUMENTAL CEMETERY AND MUSEUM COLLECTIONS IN GENOA (ITALY). Simona Scrivano,1 Laura Gaggero1 and Adelmo Taddei2 1 Department of Earth, Environment and Life Sciences, University of Genoa, Corso Europa 26, I-16132 Genoa 2 Museum of Sant'Agostino in Genoa, Piazza Sarzano 35r, I-16128 Genoa Abstract The weathering of marble sculpted pieces, selected from different, well-known, environmental exposures was the object of a systematic multi-scale diagnostic study. Our aim was to connect each decay pattern detected on the case studies to their conservation environment, and to assess correlations useful in case the preservation data or part of the historical record are lacking. This study addressed the weathering of: 1) A c. 100 meters long, south west facing wall, clad in slabs of different lithotypes, installed between 1900 and 1970 in the Staglieno Monumental Cemetery in Genoa, as example of outdoor exposure. 2) Several religious and civil sculptures dated to the XIII century AD, affected by both confined and outdoor exposure until the XIX century, then ascribed to the heritage of Genoa city, at present conserved in the Museum of Sant’Agostino in Genoa. 3) One piece of marble architectural ornament from a XIV century church, buried between 1820 when the building was demolished and 2003, as well conserved at the Museum of Sant’Agostino in Genoa. The visual analyses of textures, mineralogical and petrographic data, associated with a photographical survey, were gathered in a custom-designed filing card. The observations by non-invasive, non-destructive technique were carried out in situ at 10x up to 255x magnification with the aid of a digital microscope, in order to characterise the alteration typologies on a surface as wide as possible. The subsequent sampling was addressed to identify the alteration products by x-ray diffraction. Afterwards, the elaboration of the deterioration indexes (Fitzner et al. 1997; Fitzner et al. 2002) was addressed to categorise andDRAFT quantify the decay. As a whole, at constant rock composition, the environment of conservation overprinted significantly different weathering patterns; furthermore, unknown changes in the collocation of pieces were unraveled and allowed completing the historical record. Keywords: outdoor alteration, gravestone, indoor environment, burial alteration, marble, Fitzner indexes 1. Introduction The obvious interest of conservation scientists towards the deterioration patterns of lithic pieces has provided useful applicative tools (ICOMOS 2008) along with valuable insights into the relationships between micro-textures and stone durability (Weber et al. 2002), decay and environment of exposure (Cassar 2002; Lefevre et al. 2002; Fassina et 1 12th International Congress on the Deterioration and Conservation of Stone Columbia University, New York, 2012 al. 2002) as well as physical properties and durability of stone (Ondrasina et al. 2002; Zeisig et al. 2002). Although the decay features are firstly related with the prevision of stone performance through time (Charola et al. 2002), most petrographic-centered studies are addressed to specific patterns of weathering, following an environmental stress upon the rock (Smith et al. 2002; Fassina et al. 2002; Maravelaki-Kalaitzaki 2005). Nonetheless, the body of data arising from diagnostic analyses is at present lacking some systematic categorisation useful to support the artistic and historical side. In addition, only limited attention was paid to the triggers of indoors alteration (Kontozova et al. 2005). For this rationale we addressed the diagnosis of decay on variably affected, artistic sculpted pieces and less valuable ornamental stones, whose exposure history was largely or almost known. In order to discriminate more precisely the causes and the effects of environmental pressure, the parameter of bulk rock composition was kept constant and the decay was ascertained merely on white or veined marbles from the Carrara quarrying district and the Southern Alps. Since the rock behaviour is predictable and known, the decay effects and extent are the parameters to investigate. Therefore, we selected case studies from clearly detectable, sometimes severe, exposure environments, aiming at the ranking of their effects and to start building up a comprehensive dataset of examples. 2. Methods (i) A preliminary historical and artistic overview from all available archive and literature sources was carried out; (ii) the assessment of the art piece-decay was acquired by following Normal 1/88 ICR CNR guidelines. A customised filing card was designed where items related with chromatic changes, ablational and accretional decay plus a fourth group of other forms were respectively gathered; (iii) on this basis, each object was digitally mapped and alteration associated with a colour and/or pattern by a Computer Assisted Design software (AutoCAD® Architecture 2012), which allowed calculating the areas affected by each deterioration pattern. The mapping was associated with thorough photographic survey at c. 10x to 250x magnification. (iv) A non-invasive analysis was followed by micro-sampling of millimetre-size chips or patinas scratched with a diamond file in the minimum amount needed for x-ray diffraction analyses. These were carried out by an automated Philips PW 1140 Xchange diffractometer installed at the DiSTAV–Unige. The instrument is equipped with the X’pert plus, X’pert data collector, X’pert data high score and X’pert organiser softwares for powder analysis of ICDD phases. (v) The weatheringDRAFT and the conservation conditions were quantified by means of the Fitzner and Heinrichs (2002) indexes (FI). Two values are recast: both the linear and progressive indices express the intensity of decay, ranging between 1 and 5. Their graphic representation provides an estimation of the overall state of conservation of the object, and diagnostic information. The FI have been calibrated for sedimentary lithotypes, whereas none or few data were available for marbles. 3. Case studies The case studies were selected within artistically or historically significant, although dramatically different, conservation environments. The Staglieno civic cemetery is a masterpiece included in the Association of Significant Cemeteries in Europe (ASCE). It was built off the city centre of Genoa following the Napoleonic Saint Cloud edict (1804) and the prescription of Carlo Alberto di Savoia (Regie Patenti 1832). 2 12th International Congress on the Deterioration and Conservation of Stone Columbia University, New York, 2012 The main realisation developed between 1835 and 1851. On the 1st of January 1851 the cemetery was officially opened to the public. This date marks just the day of the inauguration ceremony, because the completion work continued over many decades. In fact, in the second half of the nineteenth century, Resasco proposed a northeastward addition with the construction of the semi-circular arcade. At the beginning of the twentieth century the Montino Portico, which houses works in Deco, and, later, the Sanctuary to the Fallen in First World War was erected. In 1955 the Sant’Antonino Portico was inaugurated, that was the last addition with monumental ambitions. Despite numerous extensions since its inauguration, the Monumental Cemetery of Staglieno reveals the neoclassical approach, ordered and centralised, still visible in the earliest project. The Staglieno Monumental Cemetery is known worldwide as an artistic and historical attraction for the impressive amount of valuable art pieces representative of over two centuries that are hosted mainly outdoors. The indoor-altered examples are two sculpted bas-reliefs and one archaeological finding, respectively exposed or conserved in the repository at the Civic Museum of Sant’Agostino (Genoa). The Museum is an Augustinian friary aged thirteenth century and restored as exhibit centre. It gathers over 4000 pieces (carved and sculpted stones e.g. Nicola Pisano, Filippo Parodi, Pierre Peuget, Francesco Maria Schiaffino sculptures, wood and metal, ceramic, glass, paintings by Luca Cambiaso, Domenico Piola and Manfredino da Pistoia) that date from the end of XII to the XVII centuries, with prevalence of medieval examples. Also frescoes and architectural fragments, as well as a precious map collection are hosted. The heritage derives from private and religious buildings. 3.1 Outdoor weathering: the gravestone gallery and the travertine chapels Within the Monumental Cemetery of Staglieno in Genoa, the Pontasso gallery is a 96 meters long suite of 24 arches built in the early twentieth century. Each arch hosts 14 loculi framed by white marble and clad with slabs of different stones, with prevalence of white or veined Carrara marble (Figure 1a) carved with Deco patterns. Slabs of Bardiglio, Verde Polcevera, Rosso Verona, and the Rosso di Levanto ophicalcite represent minor occurrences. Most slabs were hung within a time interval of about 20 years, so the start of the exposure can be considered coeval, at constant lithology composition (i.e. Carrara marble). The gallery is exposed to the SW, and is a continuous exposure with impressive examples of differential weathering controlled by microclimates and local DRAFTtopography. In particular, the gallery exists on an embankment of the Pontasso stream, channelized