Nicola Ludwig

Field and Laboratory Spectroscopic Methods for the Identification of Pigments in a Northern Italian Eleventh Century Fresco Cycle

The pigments of an XI-century fresco cycle in a small pre-alpine church of northern Italy were characterized by means of field techniques, in particular imaging spectroscopy, and laboratory spectroscopic techniques, namely total reflection X-ray fluorescence, micro-Raman, micro-Fourier transform-Raman, and micro-Fourier transform infrared spectroscopies, thus achieving a complete identification of the ancient painters palette. Advantages and limitations of each technique in its application to the study of fresco pigments are discussed. The artistic value of the fresco cycle and the religious role in the year 1000 of the church where it is located (S. Michele Arcangelo in Gornate Superiore, Varese, Italy) were demonstrated by the precious and elaborate materials used by the painter. Different pigments were used for different hues of the same color, e.g., azurite, carbon, and the most precious lapis-lazuli for blue, while mixtures of pigments were recognized in details having a particular tint, e.g., lapis-lazuli and minium for violet.

Optimal thermographic procedures for moisture analysis in building materials

The presence of moisture in building materials causes damage second only to structural one. NDT are successfully applied to map moisture distribution, to localize the source of water and to determine microclimatic conditions. IR Thermography has the advantage of non-destructive testing while it allows to investigate large surfaces. The measures can be repeated in time to monitor the phenomenon of raising water. Nevertheless the investigation of moisture in walls is one of the less reliable application of Thermography IR applied to cultural heritage preservation. The temperature of the damp areas can be colder than dry ones, because of surface evaporation, or can be warmer, because of the higher thermal inertia of water content versus building materials. The apparent discrepancies between the two results are due to the different microclimatic conditions of the scanning. Aim of the paper is to describe optimal procedures to obtain reliable maps of moisture in building materials, at different environmental and microclimatic conditions. Another goal is the description of the related energetic phenomena, which cause temperature discontinuities, and that are detected by thermography. Active and passive procedures are presented and compared. Case studies show some examples of procedures application.

Dynamic IRT for the frescoes assessment: the study case of Danza Macabra in Clusone (Italy)

IRT technique applications for the detection of the plasters defects in historic buildings are widely documented by scientific literature. Previous studies demonstrated the advantages of tomographic techniques to obtain quantitative results by IRT. With a quantitative approach, the dynamic measures of IRT, versus time and maximum value of thermal contrast, allows to locate the delamination and calculate its volume inside the thickness of the plaster. Nevertheless, effects are not prominent if compared with the ones caused by the interaction between surface and irradiation. Moreover these effects are lower than the noise due to the approximation of the spectral coefficient value. Authors already showed that the multispectral evaluation of the reflectance coefficients, in the range of visible and near IR, contributes to a proper evaluation of the thermograms shot on surfaces affected by chromatic alterations. In the study case, the evolution of the surface temperature in time allows to quantify the effects of spectral absorption (absorbance) in the thermograms. By comparing the thermograms to the maps of damages and intervention, it has been possible to correlate the materials and its state of conservation to the evolution of the thermal profile corresponding to each analyzed area.

Potential application of thermography (IRT) in animal production and for animal welfare. A case report of working dogs

INTRODUCTION The authors describe the thermography technique in animal production and in veterinary medicine applications. The thermographic technique lends itself to countless applications in biology, thanks to its characteristics of versatility, lack of invasiveness and high sensitivity. Probably the major limitation to most important aspects for its application in the animal lies in the ease of use and in its extreme sensitivity. MATERIALS AND METHODS This review provides an overview of the possible applications of the technique of thermo visual inspection, but it is clear that every phenomenon connected to temperature variations can be identified with this technique. Then the operator has to identify the best experimental context to obtain as much information as possible, concerning the physiopathological problems considered. Furthermore, we reported an experimental study about the thermography (IRT) as a noninvasive technique to assess the state of wellbeing in working dogs. RESULTS The first results showed the relationship between superficial temperatures and scores obtained by the animal during the behavioral test. This result suggests an interesting application of infrared thermography (IRT) to measure the state of wellbeing of animals in a noninvasive way.

Thermographic inspection of cracks in the mixed materials statue: Ratto delle Sabine

This work describes a simple use of active Infrared Thermography developed to detect the level of weathering of a statue with respect to cracks observed on the surface. The statue “Ratto delle Sabine” of Giambologna is exposed in the Galleria of the Accademia in Florence-Italy and was the object onto which the methodology of analysis was used. Radiographic analyses indicated that the statue was originally made out of composite materials (mainly wood and tissue at the inner part and raw clay at the outer part). This artefact is a model which was originally not conceived to last for a long time and nowadays shows severe cracks. Thermal investigations have been done in laboratory and in field to evaluate the level of weathering of the statue, in particular related to the previously mentioned cracks. The main purpose of this study was to find a way to detect and/or demonstrate eventual interconnections between the different cracks and to evaluate the state of weathering of the statue. The methodology is based on insufflating hot air locally into the cracks of the statue during a short time, monitoring at the same time the surface temperature evolution near to the place of inflow and observing if the hot air emerges at the opposite side.To assess the eventual danger of this methodology of blowing in hot air locally, preliminary tests were made in laboratory using samples composed out of different combinations of materials (raw clay, wood, tissue, etc.) similar to the ones composing the statue. Such tests have shown that a heating time of a few minutes was sufficient to highlight the leaking of warm air from the inflow opening to the back side and this without an excessive temperature increase of the surface near the infiltration point. This was done respecting the conservation restrictions and rules for the these materials. Results in lab and field demonstrated the potential efficiency of the method to monitor the conservation state of this fragile artefact. In this specific application the method allowed to identify four critical points in the “Ratto delle Sabine” model.

A multidisciplinary materials characterization of a Joannes Marcus viol (16 th century)

BackgroundSeveral musical instruments in the past centuries were decorated with engravings, inlays, or paintings. This paper focuses on an integrated approach to detect and characterize the kind of dyes when used for the decorations. The multi analytical campaign was performed on a viol made by Joannes Marcus in the second half of the 16th century. The instrument has been shattered during World War II, and the fragments are now held in Conservatorio Giuseppe Verdi in Milan; they still conserve the original black and white purflings and the painted decorations. The study is of critical importance since Joannes Marcus worked in the sixteenth century and, in this very period, some executive features were introduced in musical instrument making, which are now veritable standards for this kind of instruments.ResultsAt first, UV fluorescence examination and reflectographic analysis have been performed on the different fragments in order to characterize, respectively, the distribution of varnishes and glues on the surface and to select the areas treated with metal-gall inks that result transparent by long wave IR reflectographic technique. The materials were therefore characterized with X-Ray Fluorescence (EDXRF), Scanning Electron Microscopy with Energy dispersive X-Ray spectroscopy (SEM-EDX) microanalyses and Micro-Infrared Spectroscopy (μFT-IR) techniques. In particular, the metallic elements present in the dyes where revealed through XRF and SEM-EDX, while μFT-IR gave details about organic binders. Elemental compositions obtained for the black decorations allowed to distinguish original parts of the fragments from those restored or remade.ConclusionsThe characterization of materials performed by our multi analytical approach, allowed us to get a deep knowledge of the technology of this ancient viol maker.In particular, the varnishes are probably composed by a diterpenic and/or triterpenic resin. In the same way, in a few traces of glue the presence of proteinaceous substances have been individuated. As for the brush-decorated area, they present a preparation layer rich in feldspars on which a black layer of carbon black particles is applied. On the other hand the purfling areas are colored by an iron-gall dye. In particular the usage of a different ink allowed to identify restored areas.

Moisture detection through thermographic measurements of transpiration

Damage due to moisture and particularly to evaporation is one of the major causes of decay of wall surfaces in ancient buildings. The evaporative rate of water in building materials can be related to the alteration (chips, gallets) caused by salts crystallization when the water evaporates through the surface of the wall. Current and future usage of NDT heavily depends on the possibility to precisely measure physical variables which present large sensitivity to small variations of water content. A NDT thermography allows us to exactly determine the evaporation rate because of both the high value of water latent heat and the high sensibility of thermographic devices. The research has been carried out both in the laboratory and on the field measuring relative humidity and temperature in a frescoed wall of the castle of Malpaga (Northern Italy). In laboratory a climatic room has been set up using a thermovision system and a temperature & RH% probes, to analyze the evaporative phenomena. A mathematical model, although approximate, is proposed to describe the energy balance of the surface where evaporation is present. The model has been applied to the fresco to correlate the temperature to the evaporation rate. This method allows us to correlate the decay, due to the capillary raise of water in the masonry, to the transpiration phenomena.

Evaluation and monitoring of water diffusion into stone porous materials by means of innovative IR thermography techniques

Abstract This paper shows the application of two innovative infrared thermography (IRT) methods for the evaluation of water transport phenomena through the outer layers of porous stone materials. An infrared camera measured: (a) the moisture stain due to the water absorption after having spilled a drop on the stone surface and (b) the ”moisture ring” around the damp surface, after the contact between a soaked round sponge and the stone surface. The time of spreading and the geometric shape of the damped area depend on the porosity of the stone material and are useful to characterize the physical stone features. In addition, monitoring the evolution of the moisture ring by IRT allows implementing and optimize the data coming from protocols of water repellent products with data coming from the “contact sponge measures”. Moreover, moisture ring test links IRT and laboratory tests characterizing the transport phenomena of liquid and water vapour in porous building materials. Thirty specimens of marble, calcarenite and sandstone were tested with steady methods (dry index and water absorption by capillarity), that validated the data provided by the two innovative IRT techniques.

Study of Fricke-gel dosimeter calibration for attaining precise measurements of the absorbed dose

A calibration method has been studied for attaining, with good precision, absolute measurements of the spatial distribution of the absorbed dose by means of the Fricke gelatin xylenol orange dosimetric system. With this aim, the dose response to subsequent irradiations was analyzed. In fact, the studied modality is based on a pre-irradiation of each single dosimeter in a uniform field with a known dose, in order to extrapolate a calibration image for a subsequent non-uniform irradiation with an unknown dose to be measured.

Ionizing radiation detection by Yb-doped silica optical fibers

Rare earths-doped silica optical fibers have shown promising results for ionizing radiation monitoring, thanks to their radio-luminescence (RL) properties. However, the use of these systems for accurate and precise dosimetric measurements in radiation fields above the Cerenkov energy threshold, like those employed in radiation therapy, is still challenging, since a spurious luminescence, namely the “stem effect,” is also generated in the passive fiber portion exposed to radiation. The spurious signal mainly occurs in the UV-VIS region, therefore a dopant emitting in the near infrared may be suitable for an optical discrimination of the stem effect. In this work, the RL and dosimetric properties of Yb-doped silica optical fibers, produced by sol-gel technique, are studied, together with the methods and instruments to achieve an efficient optical detection of the Yb3+ emission, characterized by a sharp line at about 975 nm. The results demonstrate that the RL of Yb3+ is free from any spectral superposition with the spurious luminescence. This aspect, in addition with the suitable linearity, reproducibility, and sensitivity properties of the Yb-doped fibers, paves the way to their use in applications where an efficient stem effect removal is required.