Heat Transfer Effects on Defect Boundaries Captured by Digital Holographic Interferometry and Infrared Thermography Workstation: an Overview on Experimental Results V. Tornari 1 & M. Andrianakis 1 & A. Chaban 1,2 & K. Kosma 1,3 Received: 29 August 2018 /Accepted: 17 June 2019 # The Society for Experimental Mechanics, Inc 2019 Abstract The heat transfer effect is observed from existing defects through heat diffusion to the sound area of the sample in long term after the sample has reached values close to the initial, signifying equilibrium with the environment. Two complementary systems providing the kinetic and thermal information of the samples were used to construct a real-time monitoring workstation in order to monitor the real-time responses of the sample after thermal excitation. Results indicate that the defect boundaries and the sound non-defect area continue to exchange thermal values long after the total area of the sample reaches initial temperature in equilibrium with environ- ment. Hence, it is here suggested that the continuous aging of artworks in controlled environments may be a result of the ongoing low thermal heat transfer from the defect to the sound areas provoking a slow but steady surface displacement and consequently deterioration mechanism against the preventive conservation measures based on environmental equilibrium. Keywords Holographic interferometry . Speckle interferometry . Infrared thermography . Fresco . Defect . Defect boundaries . Heat transfer . Diagnostics . DHSPI . SIRT Introduction Heat diffusion and heat convection constitute mechanisms through which the flow of extra thermal energy and energy exchange between the boundaries of different systems of solids and fluids take place, and require their physical contact with the immediate vicinity. As a consequence, when a body has a higher temperature from its surroundings the heat flows from the region of higher temperature to the region of lower temperature in order for the body to achieve same temperature with its surroundings acquiring thermal equilibrium [1, 2]. The observation of such heat transfer mechanisms on real artworks that are susceptible to temperature and humidity changes and carry multiple internal boundaries of structures due to existing defects, detachments, and other types of dis- continuities, often constituting an ensemble of bodies within the body of the artwork, are of fundamental importance for the conservation of cultural heritage [3–5] and form the subject of this study. Digital Holographic Speckle Pattern Interferometry (DHSPI) and Stimulated Infrared Thermography (SIRT) con- stitute well established techniques through which heat transfer and induced mechanical deformations are investigated. Usually an external heat stimulus thermally excites the object under investigation and, through heat flow to the inner mate- rial, possible irregularities, are recorded as distinct fringe pat- terns and hot regions in the acquired interferograms and ther- mographs, respectively. When a material under study is heated with radiators from the surface, the temperature of the surface will rise in an abrupt manner. The speed at which the heat front dissipates inside the * V. Tornari vivitor@iesl.forth.gr; http://www.forth.iesl.gr M. Andrianakis http://www.forth.iesl.gr A. Chaban http://www.forth.iesl.gr K. Kosma http://www.forth.iesl.gr 1 Foundation for Research and Technology-Hellas / Institute of Electronic Structure and Laser, N. Plastira 100, Voutes, 73 111 Heraklion, Crete, Greece 2 Department of Cultural Heritage: Archaeology and History of Art, Cinema and Music, University of Padova, Palazzo Liviano - Piazza Capitaniato 7, 35139 Padova, PD, Italy 3 Centre for Plasma Physics and Lasers, Hellenic Mediterranean University, Tria Monastiria, 74100 Rethymnon, Crete, Greece Experimental Techniques https://doi.org/10.1007/s40799-019-00336-w