OPTO-CH 2020 meets IPERION-CH.gr,  June 29th - July 03rd

Optical technologies offer unique prospects as regards conservation and diagnostics in Cultural Heritage, yet their use in real-life conservation treatments is rather sporadic and far from routine, despite a number of brilliant applications, for example the Athens Acropolis conservation campaigns. Among the main reasons for the rare use of lasers in conservation practice is the lack of training opportunities.

The OPTO-CH series of summer courses have as main goal to present advanced optical technologies in Cultural Heritage (CH) science and conservation to scientists and young conservation professionals within a training setting that will combine lectures from experts with practical hands-on experimental sessions that will enable participants to get a real feeling on how to use a number of advanced optical tools for analysis and characterisation of materials and surfaces.

Areas of focus will include:

A. MATERIALS ANALYSIS WITH OPTICAL SPECTROSCOPY

1. LIBS, LASER INDUCED BREAKDOWN SPECTROSCOPY

Laser Induced Breakdown Spectroscopy enables the determination of the elemental composition of materials on the basis of the characteristic atomic emission from a micro-plasma produced by focusing a high-power laser on, a solid surface. LIBS has been used in a wide variety of analytical applications for the qualitative, semi-quantitative and quantitative analysis of materials. It is rapid, non-destructive and can be used in-situ, therefore its application in the field of cultural heritage is considered very useful.

Objective of this module is to demonstrate the analytical capabilities of LIBS in the field of cultural heritage. Following a brief introduction in the main physical principles of the technique, and instrumentation aspects, participants will use LMNTII+ (eLemNT-II plus) a mobile LIBS instrument, especially developed for CH applications, to analyze materials on various model samples but also on selected real objects.

2. RAMAN SPECTROSCOPY

Raman spectroscopy is a well-known analytical technique that probes vibrational and other low-frequency modes (motions) in molecules and materials. As a result, it provides an accurate look into chemical bonding, thereby enabling identification of various types of materials, both inorganic and organic. The technique is rapid, non-destructive and can be used in-situ, with increasing applications in the field of cultural heritage, for example, in the identification of pigments and minerals, binding media and varnishes, corrosion and degradation products. It features high sensitivity and specificity enabling analysis of a wide variety of organic, inorganic and bio-materials, often directly on the object under study, non-invasively, at short times and with superb spatial resolution when the analysis is performed on a Raman microscope.

Objective of this module is to demonstrate how Raman microscopy is used as an analytical and diagnostic tool in the field of cultural heritage. Following a brief overview of the main physical principles and basic instrumentation of Raman spectroscopy, measurements will be conducted on a mobile Raman micro-spectrometer. Participants will study model samples and real objects, collecting Raman spectra, learning how to extract analytical information and evaluating practical aspects of the technique.

3. DIFFUSE REFLECTANCE SPECTROSCOPY

Diffuse reflectance (DR) spectroscopy is an established non-destructive method that permits rapid data acquisition and enables quick surveying of the artefacts providing effective characterisation of various types of coloured materials. In diffuse reflectance a broadband light beam is directed into the sample where it is transmitted, scattered and absorbed throughout the sample material. The fraction of the light that is reflected, diffusely scattered within a sample and returned to the surface is considered to be the diffuse reflection. Due to the simplicity of the method, a broadband light source and a low resolution spectrometer can be used for the implementation of reflectance setup capable of providing consistent spectra of materials.

Objective of this module is to demonstrate the capabilities of diffuse reflectance spectroscopy in the field of pigment identification. Following a brief introduction in the main principles of the technique, and instrumentation aspects, participants will use the diffuse reflectance module attached in the mobile LIBS instrument, to analyze pigments on various model samples but also on selected real objects.”

 

B. OPTICAL COHERENCE METROLOGY FOR STRUCTURAL DIAGNOSIS

Optical coherent metrology is the measurement of differential displacement of surface points with optical laser interferometry techniques. Holographic interferometry records phase changes of an expanded laser beam in higher spatial resolution photosensitive mediums. Being a non-contact and non-destructive optical method holographic Interferometry allows for qualitative and quantitative structural analysis of the examined objects. It is a safe, full-field technique using divergent beams and it is independent of the shape, surface texture, and complexity of the examined materials. It shows the surface response to hidden active defects, threatening environments and treatments, by visualizing rapidly the surface reaction to external perturbations. In-situ monitoring in real-time conditions, risk priority maps, structural documentation and routine impact assessment, before or after treatment, transportation, and handling are holographic Interferometry’s exploited applications.

Objective of the module is to demonstrate the diagnostic potential of interferometric techniques as regards the visualisation and assessment of invisible and hidden structural defaults and problems in the bulk of objects and structures and the evaluation of their structural condition in relation to their environment. Following a brief introduction to the main physical principles of the technique, lab demonstrations will be carried out with DHSPI, a portable instrument, developed at IESL-FORTH. In the lab session the participants will have the chance a) to get an overview of conventional optical holographic interferograms and generation of optical three-dimensional holograms, b) to record digital holographic speckle interferograms of technical samples with known defects in order to evaluate their structural condition and c) to simulate microclimate conditions in environmental chamber in order to assess the influence of environmental changes to the objects/surfaces on the basis of their optical coherence response to abrupt changes of relative humidity and temperature.

 

C. OPTICAL AND PHOTOACOUSTIC IMAGING AND MAPPING

Spectral Imaging is based on the fact that materials absorb, reflect and emit light in a manner that depends on their molecular composition and shape. Multi-spectral imaging combines a high spatial resolution image with multiple point reflectance spectroscopy, enabling the detailed mapping of the individual layers (varnish and paint) that compose an artwork. The artwork is examined in a wide range of spectral bands (350 nm– 1200 nm) expanding thus the imaging potential of the object to spectral areas in which the human eye is not sensitive, namely the ultraviolet (350 nm- 400 nm) and the near infrared (700 nm- 1200 nm). In these spectral ranges light penetrates matter in variable ways revealing information from different layers of the object. In addition, in the visible region spectral imaging enables the analysis with higher spectral resolution (13 bands) than the human eye (3 bands), enhancing the differentiation of pigments/layers with similar color perception. Consequently, the artworks can be studied stratigraphically, revealing thus information on their history, composition and structure as well as on their restoration interventions.

Objective of this module is to demonstrate the analytical capabilities of Multi Spectral Imaging in the field of cultural heritage. In this session, a brief introduction to the main physical principles of the technique will be presented, followed by a demonstration of the analysis on selected samples. Multi-spectral images will be collected with IRIS, a portable instrument developed at IESL-FORTH.

 

D. LASER ABLATION METHODOLOGIES FOR CLEANING PURPOSES

Laser cleaning relies on the ablation effect, as a result of intense and short-pulse irradiation at wavelengths that are strongly absorbed by the substrates. This is a quite complex process, closely dependent on material properties and laser parameters, which upon optimisation may result to safe and controlled material removal with minimal thermal load or damage (if any) to the substrate.

Objective of this module is to demonstrate the use of laser irradiation for the controlled and safe removal of various types of unwanted over-layers (pollution accumulations, corrosion layers, burial encrustation, aged varnishes and protective coatings, over-paintings etc) from CH objects and monuments (i.e. stonework, metals, paintings etc.) Following a brief introduction to the main physical principles of laser ablation, and several lectures on previous experience, laser cleaning tests will be performed on technical samples with the aim to determine critical thresholds and optimize the cleaning intervention.

Important Dates

  • OPTO-CH 202 summer course is Cancelled
  • Application deadline: April 26
  • Notice of Acceptance:  April 30

OPTO-CH 2020 POSTER