IN SITU ACOUSTIC IMAGING TO REVEAL GLAZE DELAMINATIONS, IN THE EARLY STAGES, IN PORTUGUESE AZULEJOS Paola Calicchia João Manuel Mimoso Dória Maria Rodrigues Costa 13 April 2011 NON DESTRUCTIVE TESTING NDT12

13 April 2011, NDT12 P. Calicchia manufacturing defects a mismatch between the coefficients of thermal expansion of the glaze and the ceramic body brings to shivering a planar compression is induced on the glaze, and may cause glaze delamination Moreover, a weak bond between the ceramic body and the glaze may cause glaze delamination a thin cavity of air is formed at the interface moisture absorption In the ceramic body salts crystallization in the cavity the glaze breaks and/or is pushed out until it falls off

P. Calicchia from J. M. Mimoso, A.S. Silva, S. X. Coentro, Studying the cracking system in 17-18th century Portuguese Azulejos with SEM SEM2010, London  A specific IR thermographic procedure, still in the early phases of experimenting for heritage azulejos, applied locally;  Investigation based on Ultrasonic Testing; no defined protocol including instrumental diagnosis to reveal glaze delamination, in particular in the early stages before lacunas become visible. a possible solution to the localization of delaminations is investigated: in situ ND acoustic technique ACoustic Energy Absorption Diagnostic Device ACEADD employed to azulejo panels for the first time 13 April 2011, NDT12 G. B. Cannelli, P. Calicchia EU Patent EP B1 (2006) US Patent US (2004) IT Patent N. RM 99 A (1999)

P. Calicchia provides acoustic absorption maps identifies anomalous acoustic absorption processes in a multilayer heterogeneous structure automatically scans an area, radiating towards the surface an acoustic wave with audible frequency content it records the reflected wave reveals sub-surface cavities by measuring the acoustic absorption coefficient mass - air spring system Mass => surface glazed layer Spring => air volume rigidity k air 13 April 2011, NDT12 M D k air F THE METHOD THE DEVICE  0 = air density ;  0 = glaze surf density; d = air cavity thickness

P. Calicchia Source S Receiver M TRANSCEIVER UNIT & TRANSDUCER CIRCUITRY SCAN UNIT DATA ACQUISITION, DATA PROCESSING, MOTION CONTROL UNIT 13 April 2011, NDT12 back reflection geometry coaxial configuration standard HW components custom SW component

p(t) = p d (t) + p r (t) = p d (t) + k r p d (t)  h(t-  ) DIR Extr h(t-  ) |H(f)| 2 = r(f) INV Extr E = ∫dt |h(t-  )| 2 = ∫df |H(f)| 2 P. Calicchia p(t) Cep[p(t)] DIR/INV Extract[C(t)]  (f) = 1 – r(f) 13 April 2011, NDT12 C(t) = C dir (t)+ k r h(t-  ) + h.o.t. Cepstrum algorithm

P. Calicchia The selected site is located in the renaissance cloister of the building, a part of the exhibition space of the museum Madre de Deus Convent, in Lisbon, which houses nowadays the Portuguese National Tile Museum - MNAz The azulejo panels, all around the cloister, are greatly affected by glaze delamination with high percentage of glaze loss 13 April 2011, NDT12

P. Calicchia ACEADD PROTOCOL & OPERATING PROCEDURE TESTSFUNCTION UNDER TEST SYSTEM FUNCTIONALITY: IN SITU Scan unit Acoustic source and transmission line Microphone and receiving line PRELIMINARY TEST: IN SITU Microphone calibration Acoustic source Frequency Response at working distance Environmental NOISE characterization Direct signal spectral analysis Cepstral background evaluation (Free-Field condition) Identification of the area of analysis System alignment & Reference Points Repeatability test ACEADD MEASUREMENT: IN SITU SCANs ACOUSTIC IMAGEs 13 April 2011, NDT12

P. Calicchia Point (i): [x i ; y i ;  i ; E i ; h i (t-  ); |H i (f)| 2 ;  (f)] NMA4 [20L x 39PTs] [0,19m x 0,38m] 10mm step 780 PTs NMA5 [17L x 21PTs] [0,16m x 0,20m] 10mm step 357 PTs Dispersion of values of indicator E: Analysis of the degree of homogeneity 13 April 2011, NDT12 from repeatability tests the max interval of values relative to the same point w rt = 0,054 w map = 0,045 w map = 0,060

P. Calicchia 30% 40% 50% 13 April 2011, NDT12 MINIMUM ABSORPTION MAXIMUM ABSORPTION THRESHOLDS DELIMITING MOST ABSORBING AREAS P. Calicchia, J. M. Mimoso “Investigation on the presence of detachments of glazed ceramic tile panels by means of non destructive acoustic mapping” LNEC Report 134/2010 (2010) REFERENCE POINT PT(14, 8) [x i ; y i ; (E RP -E i )/E RP ]

P. Calicchia 30% 40% 50% 13 April 2011, NDT12 MINIMUM ABSORPTION MAXIMUM ABSORPTION THRESHOLDS DELIMITING MOST ABSORBING AREAS P. Calicchia, J. M. Mimoso “Investigation on the presence of detachments of glazed ceramic tile panels by means of non destructive acoustic mapping” LNEC Report 134/2010 (2010) REFERENCE POINT PT(4, 6) [x i ; y i ; (E RP -E i )/E RP ] f abs = 11,3kHz d = 13  m

P. Calicchia ACKNOWLEDGEMENTS This work was possible thanks to the efforts of many special people. Thanks to the team of the Stone & Ceramics Division of the Department of Materials of LNEC; thanks to the colleagues of the Institute of Acoustics and Sensor of CNR. A special thank to the Director and the staff of the Portuguese National Tile Museum (Museu Nacional do Azulejo). 13 April 2011, NDT12  Insight into the glaze delamination process, for preventive conservation actions;  Definition of a reliable diagnostic protocol, integrating different and complementary methods, such as the IR thermography and the acoustic method, aiming at the detection of subsurface cavities in the early stages, before glaze loss occur;  Insight into the acoustic response of ceramics, through lab test and comparison with IR thermography;  Technological development of ND acoustic diagnostic device ;  Definition of a proper operating procedure, assessment of the method reliability on different artefacts (frescoes, ceramics, mosaics) and in different operating conditions.