IRT has been used as a first investigation in laboratory to detect pioneer biofilms which help the biological fouling of stone monuments. Biological development is often removed because of the unsightly aspect and it favours stone deterioration with mineral dissolution by production of organic acids, salting induces physical damage which helps to the development of macroscopic vegetation. Biological deterioration leads to the degradation of stone monuments and to the irretrievable loss of artefacts for our Cultural Heritage. Two limestones, Courville and Savonnieres stones used in major buildings in eastern France and the surroundings of Paris have been investigated. On first, stone samples have been exposed in outdoor test to favour the natural colonisation of first micro-organisms. They have been collected after six months exposure and compared to three non-colonised stones throughout IRT measurements of stone surfaces pulsed by a flux of photons. First results on Courville stone, showed Look Up Table (LUT) was important to emphasize slight variations of static images between stones with biofilm and control stones without it. Moreover, mathematical post-processing as SVD, usually applied to decrease thermal artefacts at the surface of a work of art and to improve detection of flaws inside it, here was to detect biofilms as surface artefacts thanks to the first EOFs. Savonnieres stone, which has different intrinsic properties than Courville stone showed static images can induced artefact associated to experimental conditions which was avoided thanks to SVD post-processing.
The study and analysis of defects in wall paintings is possible by stimulated infrared thermography, this approach is of great interest to the scientific community responsible for the conservation and restoration of these works of art. The work presented consists in identifying the best way to stimulate and analyze the thermal signals measured on these works of art in order to reveal defects invisible to the naked eye such as internal decohesions. In the case of wall paintings, for example, optical effects associated with the presence of a pictorial layer can degrade this detection. To do this, we compared two excitation modes of an academic sample, excitation using conventional halogen sources emitting in the visible and near infrared and an excitation source emitting in the mid-infrared. We compared the two excitation modes and applied a postprocessing to these two experimental approaches: SVD. The results presented made it possible to observe the interest of infrared sources and the additional contribution made by post-processing of the SVD type.
Infrared thermography is a non-destructive testing technique that affects many areas. This technique of analysis is, for example, very interesting in the field of restoration and conservation of heritage works. The possibilities of active thermography can help in the early detection of defects in works of art and their characterization. In this work we will demonstrate that it is possible to detect old restorations in frescoes and murals by flash method. This new possibility offered by thermography will make it possible, for example, to verify the compatibility of a restoration with the original work, which can prevent the appearance of a defect and may allow the conservator to follow up on restoration. First we will show the feasibility of this approach on a laboratory specimen containing different types of clogging materials and then present results of analysis carried out in situ at one restoration sites that reveal the possibility of locating these restorations but also to characterize the pictorial technique used in this one.
Electron microscopic observation of the surface of orthodontic arches reveals observable differences between new and used arches after four weeks in the mouth. This qualitative observation led us to consider their study by stimulated infrared thermography. These dental arches consist of a nickel-titanium (NiTi) shape memory alloy and are highly stressed during the stay in the mouth. Over the months, there will be evolution of their mechanical properties with multifactorial causes. In this study, we will demonstrate that it is possible to differentiate between the used arcs from the new arcs by observing their thermal response during a controlled heating.
Such developments come from conservation experts in the community of cultural heritage - encompassing artworks, museum artifacts or historical monuments - for less intrusive and non-destructive tools to gain information about the subject. Increasingly the demand is for information regarding internal structures and indications of life histories and behaviors of an object. As it is well known, the deterioration due to the capillary rise of water through the walls is a very widespread problem. In this paper, a study of Stimulated Infrared thermography and Evanescent-Field Dielectrometry was applied to a non-destructive mapping, in situ, and in a semi-quantitative way the distribution of water, salt and the structural deterioration induced in a wall of the 13th century of the abbey’s church of Chaalis. Complementarity of the both techniques will be underlined. The Stimulated Infra-Red Thermography (SIRT) is a contact free technique and allows the detection of plaster layers delamination of masonry. Evanescent-Field Dielectrometry (EFD) is a recent diagnostic method based on dielectric spectroscopy at microwave frequency. The measuring instrument is a portable resonant microwave device for mapping the water content and salinity on flat surface up to a depth of 2–3 cm in real time, in a non-destructive way. The method detects the water content and salt concentration in frescoes and walls by estimating the dielectric properties of tested porous materials that is viewed as a “binary” dielectric mixture consisting of bulk material and water, by the contrast between the dielectric constant of a dry material and water. According to the resolution of the optics, the SIRT has a less lateral resolution and more limited in depth, but it is easy to implement and can be used on-site, like in scaffolding conditions. Moreover, this technique gives an overview at a larger scale (metric) than EFD (centimetric).
The abbey’s church of Chaalis, in the North of Paris, was founded by Louis VI as a Cistercian monastery on 10th January 1137. In 2013, in the frame the European Commission's 7th Framework Program project CHARISMA [grant agreement no. 228330] the chapel was used as a practical case-study for application of the work done in a task devoted to best practices in historical buildings and monuments. In the chapel, three areas were identified as relevant. The first area was used to make an exercise on diagnosis of the different deterioration patterns. The second area was used to analyze a restored area. The third one was selected to test some hypotheses on the possibility of using the portable instruments to answer some questions related to the deterioration problems. To inspect this area, different tools were used:
-Visible fluorescence under UV,
- THz system,
- Stimulated Infra-Red Thermography, SIRT
- Digital Holographic Speckle Pattern Interferometry, DHSPI
- Condition report by conservator-restorer.
The complementarity and synergy offered by the profitable use of the different integrated tools is clearly shown in this practical exercise.
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