A Combined Non-Invasive Approach to the Study of A Mosaic Model: First Laboratory Experimental Results.

Antonina Chaban,Michalis Andrianakis,Rita Deiana,David Giovannacci,Vivi Tornari,Vincent Detalle

doi:10.3390/jimaging5060058

Abstract

This paper presents first laboratory results of a combined approach carried out by the use of three different portable non-invasive electromagnetic methods: Digital holographic speckle pattern interferometry (DHSPI), stimulated infrared thermography (SIRT) and holographic subsurface radar (HSR), proposed for the analysis of a custom-built wall mosaic model. The model reproduces a series of defects (e.g., cracks, voids, detachments), simulating common deteriorated, restored or reshuffled areas in wall mosaics. DHSPI and SIRT, already well known in the field of non-destructive (NDT) methods, are full-field contactless techniques, providing complementary information on the subsurface hidden discontinuities. The use of DHSPI, based on optical imaging and interferometry, provides remote control and visualization of surface micro-deformation after induced thermal stress, while the use of SIRT allows visualization of thermal energy diffusion in the surface upon the induced thermal stress. DHSPI and SIRT data are complemented by the use of HSR, a contact method that provides localized information about the distribution of contrasts in dielectric permittivity and related possible anomalies. The experimental results, made by the combined use of these methods to the identification of the known anomalies in the mosaic model, are presented and discussed here as a contribution in the development of an efficient non-invasive approach to the in-situ subsurface analysis of ancient wall mosaics.

Highlights

The use of the mosaics as a type of wall decoration is documented in ancient times, since theRoman period [1,2,3]
Since the surface height of the mosaic sample is variable, the acquisitions were performed on six small areas (25 × 25 cm and 20 × 30 cm)
The changes in fringes density are correlated to different properties in underlying materials

Summary

Introduction

The use of the mosaics as a type of wall decoration is documented in ancient times, since theRoman period [1,2,3]. Mosaics became the main wall decoration of the churches in the Byzantine art, with a large spread in the early Christian age and during the Medieval period [4,5]. After the decline of Byzantine mosaic art in the 13th century, this kind of wall decoration, along with wall paintings, recovers its importance during the Renaissance period [1,2,3]. J. Imaging 2019, 5, 58 vaults, and cupolae are documented up to the 19th century in Europe, as in Russia, while in the Orient the use of the mosaics in walls decoration is widely spread during the millennia in the Islamic art, in particular in the Iranian decoration history [1,2,3,6]. Considering the large use of the wall mosaics in historical buildings in high and not accessible parts (e.g., vaults or cupolae), the preservation of these decorations requires the adoption of the most adequate strategies for their quick monitoring and intervention, if needed

Methods

Results

Discussion

Conclusion