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Il tema della conservazione in situ di opere murali outdoor è al centro, negli ultimi tempi, di un accesso dibattito soprattutto in relazione al differente approccio da adottare a seconda che l’opera sia un murale oppure un dipinto murale. Fino a pochi anni fa l’interesse crescente per la conservazione della cosiddetta “street art” ha portato alla ricerca di nuove metodologie e alla sperimentazione di nuovi prodotti da applicare sulle opere al fine di garantirne la durabilità nel tempo. Attualmente il restauratore/conservatore che si trova di fronte ad un’opera di “Urban Art” deve adottare un approccio conservativo molto più cauto ponendosi alcune questioni preliminari legate alla reale necessità di proteggere e salvare le opere di arte urbana realizzate da artisti che lavorano in ambienti esterni.

II deterioramento dei manufatti lapidei e ceramici sommersi è un processo che si sviluppa attraverso eventi fisici, chimici (abrasione, deposizione, ossidazione e riduzione ) e biologici attraverso la colonizzazione biologica da parte di microrganismi prima e di macrorganismi successivamente (Lopez-Arce et al. 2013, Aloise et al. 2013), in quanto i materiali forniscono un substrato di attacco per la loro crescita. In un recente progetto PRIN dal titolo "Approcci innovativi per lo studio sperimentale di manufatti ceramici “sommersi" sono stati valutati gli effetti delle diverse condizioni di giacitura dei reperti ceramici e del conseguente deterioramento, mediante uno studio multidisciplinare (chimico, mineralogico, fisico) su provini ceramici che riproducono sperimentalmente le caratteristiche di composizione e struttura di campioni archeologici rinvenuti all’interno di relitti sommersi. I campioni preparati sono stati posti in due vasche che simulavano due diverse condizioni di fondali marini caratterizzate da condizioni ambientali ossidanti e riducenti. La sperimentazione ha mostrato anche che i provini di ceramica sommersi presentano una colonizzazione che varia secondo il tipo di materiali, manifattura degli stessi (es. preparazione e cottura delle ceramiche) e l'ambiente in cui essi si trovano (es. profondità, ambiente aerobico o anaerobico, copertura ecc .). Infatti, è stato osservato che la colonizzazione è avvenuta in maniera differente nei i vari tipi di impasti e in tempi brevi, a secondo delle condizioni ambientali (maggiore in ambiente aerobio e minore in ambiente riducente anaerobico), in base alla loro composizione, mentre il tempo di esposizione sembra solo intensificare il processo di colonizzazione. Per quanto riguarda i gruppi coinvolti in ambiente ossidante si nota una maggiore biodiversità con alghe verdi e brune quali componenti del phytobenthas, barnacles, briozoi e molluschi bivalvi e policheti come zoobenthos, con scarsa microfauna e foraminifera. Per quanto riguarda i batteri, la maggior parte degli isolati sono batteri eterotrofi ubiquitari, mentre sono stati raramente osservati batteri solfo-ossidanti. Tali microrganismi quando rilevati, sono stati in grado di ossidare sperimentalmente il tiosolfato in solfato, e anche se non in quantità rilevanti, hanno precipitato cristalli di gesso sulla superficie di provini di marmo immersi nello stesso terreno. In ambiente riducente, i differenti campioni esposti, presentavano una minore colonizzazione rispetto ai rispettivi campioni in ambiente ossidante. La biodiversità di conseguenza appariva ridotta anche se presenti alghe verdi e brune, raramente, policheti e barnacles. Inoltre, i batteri solfato-riduttori sono stati sempre isolati e le prove svolte hanno dimostrato che oltre che capaci di ridurre il solfato a H2S, precipitavano fasi carbonatiche per più calcite. Tali dati, sebbene preliminari, confermano quindi un coinvolgimento batterico, già nelle prime fasi di immersione in acqua; essi aderendo sulla superficie favoriscono, da una parte l’adesione sulla superficie dei macrorganismi, ma contribuiscono già nelle fasi iniziali alla precipitazione di fasi minerali sui reperti archeologici sommersi e ai processi di formazione di concrezioni minerali.

This paper deals with the proposal of an original experimental methodological approach specifically designed for appraising any compositional alteration and/or contamination of archaeological ceramics after the protracted contact with seawater. A series of ceramic test-pieces (briquettes and cylinders) were purposely manufactured by mixing selected calcareous or non-calcareous clays with different varieties of sieved sand temper. The aim was to reasonably simulate the ceramic pastes most frequently found in the shipwrecks recovered in the coastal areas of western Mediterranean. The used raw materials were previously characterized in terms of mineralogical and chemical composition (XRPD, XRF). The obtained test-pieces were fired under oxidizing conditions at predetermined temperatures (800 and 950 degrees C) in a traditional ceramic kiln and their chemical composition was analyzed by XRF spectrometry. Briquettes were firstly fixed into customized Ertacetal (R) holders and then placed in open sea-bed environment under monitored oxidizing or reducing conditions by the Italian CNR-IAMC dockside at Granitola, north-western Sicily. At the same time, two customized glass containers for working in a confined system under continuous seawater flow were designed and realized. They were filled with bottom sediments rather different in size in order to produce either reducing or oxidizing microenvironments below the water-sediment interface. Cylinder shaped test-pieces were placed in the sediment of both the glass containers. Weekly monitoring of temperature, salinity, conductivity, pH, Eh, dissolved oxygen was carried out in both the above-described experimental settings. Comparative (before/after) XRF analyses, after 3 months of exposure to seawater, were performed on the experimental ceramic briquettes and cylinders. The obtained results provided preliminary evidences that the proposed experimental strategy is efficiently working and a number of not negligible changes concerning major and trace elements were pointed out just after such a restricted time of exposure to seawater

The present work is aimed at the investigation of the ceramic bulk and pigmented glazed surfaces of ancient potteries dating back to XIX century A.D. and coming from the charming archeological site located in the Medieval Agsu town (Azerbaijan), a geographic area of special interest due to the ancient commercial routes between China, Asia Minor, and Europe. For the purpose of the study, complementary investigation tools have been exploited: non-destructive or micro-destructive investigation at elemental level by ion beam analysis (IBA) techniques, by using Rutherford Backscattering Spectrometry (RBS), Proton-Induced X-ray Emission (PIXE) spectroscopy and ion-microbeam analysis, and chemical characterization at microscopic level, by means of synchrotron radiation (SR) Fourier transform infrared (FTIR) microspectroscopy. The acquired information reveals useful for the identification of the provenance, the reconstruction of the firing technology, and finally, the identification of the pigment was used as a colorant of the glaze.

The present contribution is part of a biennial research project funded by the Italian Ministry of Education, Universities and Research (MIUR). This study, currently in progress, deals with innovative experimental approaches applied to the chemical, mineralogical and physical transformations occurring during the prolonged permanence of archaeological ceramic finds in seawater environments as well as to restoration and conservation issues of the same underwater artifacts. The experimental approach used in this research consisted in the manufacture of ceramic test-pieces (briquettes) and their successive placing in underwater environment. This work aims at assessing how textural and compositional parameters along with firing temperatures of a ceramic paste could affect total porosity, pore size distribution and kinetics of capillary water absorption. A further purpose is concerned with the study of the potential modification of porosity and pore size distribution in the same ceramic bodies after immersion in seawater (3 and 6 months). The study was carried out using a multi-technique approach including investigations through polarized light microscopy (PLM), capillary water absorption test, mercury intrusion porosimetry (MIP) analyses and theoretical calculation of salt crystallization pressures. The obtained results show a different behavior of the six experimental pastes as a function of their compositional and textural features as well as pore size distribution and firing temperatures. These parameters, in various extents, have been found significantly influencing the kinetics of water absorption and the susceptibility of ceramic artifacts to salt crystallization processes, with important implications on conservation procedures needed before the musealization.

This paper deals with the comparative evaluation of different procedures of salt extraction designed for archaeological ceramics from submarine burial environments. The experimental work was carried out on a particular type of late-Roman cooking ware finds (Pantellerian ware) found in a shipwreck near the shoreline of the Island of Pantelleria (Sicily). The studied ceramic test-pieces were first recognised in terms of bulk characteristics (mineralogy, petrography and chemistry). SEM-EDS observation allowed verification of the presence of various secondary minerals at the surface and in the pore spaces formed after the prolonged permanence in seawater under oxidising or reducing conditions. Pore-size distribution was also determined in the same fragments that had been subjected to the salt extraction routines. Three salt extraction methods were tested: two methods based on diffusion processes (water immersion under stationary conditions and under mechanical stirring conditions) and one method based on both diffusive and advective processes (multiple packages of sepiolite). The obtained experimental data allowed us to identify strengths and weaknesses of the tested procedures with practical spin-off for archaeologists and restorers (efficiency, kinetics, compatibility with the ceramic substrate, costs and simplicity of use). Salt extraction under mechanical stirring was the most effective method and, for this reason, is suitable for laboratory fieldwork during or immediately after submarine archaeological excavations. Similar advantages are also intended for the preliminary treatments of the most precious findings prior to museum storage.

Salt crystallization is widely recognized as a cause of deterioration of porous building materials. In particular, the crystallization pressure of salt crystals growing in confined pores is found to be the main cause for damage. The aim of this study is to better understand the degradation of porous rocks induced by salt crystallisation and correlate such processes with the intrinsic characteristics of materials. With this intend, an experimental salt weathering simulation has been carried out on two limestones widely used in the Baroque architecture of eastern Sicily. A systematic approach including petrographic, porosimetric and colorimetric analyses, was used to evaluate the correlation among salt crystallisation, microstructural and chromatic variations of limestone. Results showed a quite different resistance of the two limestones to salt damage, and this was found to be strongly dependent on their pore structure and textural characteristics.