Characterization of black crusts in the Palace of Knossos, Crete, Greece

Fernanda Carvalhoa*, Antonella Curullib, Elissavet Kavoulakic, Elpida Politakic, Elissavet Katsavelic, Aristeidis Dokometzidisc, Maria Margarida R. A. Limaa, Giampiero Montesperellid, Sara Roncae, Hugo Águasa, Giuseppina Padelettib, João Pedro Veigaa 

*aCENIMAT/I3N—Centro de Investigação em Materiais, UNINOVA—Instituto de Desenvolvimento de Novas Tecnologias, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal

bCNRConsiglio Nazionale delle Ricerche, ISMN—Instituto per lo Studio dei Materiali Nanostrutturati, Via Salaria km 29.5, Monterotondo, 00015 Rome, Italy

cEPHORATE of Antiquities of Heraklion, Xanthoudidou & 1 Chatzidaki str, Heraklion 71202, Greece

dDipartimento di Ingegneria dell’Impresa, Università di Roma Tor Vergata, INSTM—Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali, via della Ricerca Scientifica, 00133 Rome, Italy

eDipartimento di Scienze della Terra, La Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Rome, Italy

Black crusts represent a factor of deterioration of cultural heritage exposed to environmental conditions. Although they do not represent a structural damage, they are responsible for modifying the original colour of the substrate, resulting in chemical and aesthetic changes in façades, sculptures and other elements constituting an historical building. The origin of black crusts can be varied, but it is relatively common that they are associated with the deposition of pollutants on substrates. Inorganic substrates such as stones, ceramic materials, mortars and cements are particularly affected by this type of problem. Conditions such as the wind direction, exposure to direct solar radiation and rainwater flow, for example, can influence the extent of damage on a surface. In the case of the Palace of Knossos, black crusts are mostly associated with the deterioration process of the recent building materials, such as the concrete. The concrete was used in the reconstruction of the Palace of Knossos, especially in the works carried out over the decades of 20 and 30 of the twentieth century. The characterization of deterioration products assists in the most assertive diagnosis and is fundamental for the definition of maintenance and prevention actions of the monument. Samples of black crusts collected at the Palace of Knossos were studied under the HERACLES project (HEritage Resilience Against CLimate Events on Site). For this study, the samples were analysed with a set of ex-situ techniques, namely optical microscopy (OM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The main objective of this study is to establish the chemical and morphological characteristics of this deterioration product, to perceive the probable causes and to assist in the preservation of the materials involved.

[1] This work was supported by the European Union’s Framework Programme for Research and Innovation HORIZON 2020 under Grant Agreement 700395 project HERACLES.

Acknowledgment to the Portuguese Foundation for Science and Technology (FCT) UID/EAT/00729/2013 and EAT/00729-3 by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT—Portuguese Foundation for Science and Technology under the project number POCI-01-0145-FEDER-007688, Reference UID/CTM/50025/2013 NOVA.ID.FCT.

Abstract presented in the Conference Materiais 2019, 14-17 Abril 2019, Lisboa, Portugal