Fernanda Carvalho^a*, Antonella Curulli^b, Elissavet Kavoulaki^c, Elpida Politaki^c, Elissavet Katsaveli^c, Aristeidis Dokometzidis^c, Angeliki Psaroudaki^c, Maria Margarida R. A. Lima^a, Giampiero Montesperelli^d, Sara Ronca^e, Hugo Águas^a, Giuseppina Padeletti^b, João Pedro Veiga^a 

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

^bCNR Consiglio 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

Efflorescence of salts are quite common in built heritage. They can occur both inside and outside the buildings, according to the conditions for the solubilization and crystallization cycles. In general, they are composed of soluble salts, but other efflorescence and crusts can also occur. The damage caused by salt efflorescence may be related both to chemical processes of dissolution of the substrate, and to the physical processes of stresses created by the development of crystals, which may result in the decay of the substrate, i.e. salt concretions and other visual changes. When the built heritage is located on an island, such as Crete, Greece, it is expected that the influence of the sea is particularly important for the formation of specific type of efflorescence and salt crusts. Under the HERACLES Project, efflorescence and salt crusts were studied in two emblematic historical monuments: the Koules fortress and the Palace of Knossos. The Koules fortress is located on the coastal line, by the sea while the Palace of Knossos is located approximately 6 km away, in the southeast direction. For this study, the samples were analysed with a set of ex-situ techniques as optical microscopy (OM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy, in order to establish the minerochemical and morphological characteristics of the crystals and to associate the possible causes of these problems.