- Photographic documentation
Details taken in grazing light to highlight any anomalies or executive details
Details shot in UV Fluorescence
- Multispectral investigations on paintings and wall decorations: reflected visible light, reflected infrared, false color reflected infrared, reflected UV, UV induced to visible fluorescence
Multispectral investigations contribute to defining the cognitive diagnostic picture of the surfaces through the combined and coordinated use of multi-frequency acquisition methods.
The infrared reflectography technique applied to paintings allows, under suitable conditions, to know details hidden under the visible layer of the paint. It can therefore make it possible to identify the presence of the preparatory drawing or any remakes, thus revealing the presence of stylistic repentances and variations in progress, as well as identifying traces of additions due to restorations and understanding the technique used by the artist. Regarding wall paintings, IR reflectography allows to view the presence of any preparatory drawing made with carbon-based materials (charcoal, ink or dusting), such as testing the presence of repainting or restorations carried out in later periods. In some cases, long wave reflectography is able to penetrate the layers of dirt or dull to verify the existence of painted surfaces that are no longer visible.
The infrared false color image (IRFC) highlights the areas made with similar pigments and allows a quick identification. Although the technique is not exhaustive as regards the recognition of pictorial materials, it still allows for the mapping of color backgrounds, attributing for many pigments a preliminary material characterization. Furthermore, all the areas subject to additional interventions are clearly and evidently represented.
Ultraviolet fluorescence imaging is one of the techniques that have been developed for the recognition of pictorial materials through non-destructive diagnostics of painted surfaces. In the mural paintings, as well as allowing the first approximation of highlighting some materials characterized by a typical fluorescence in the pictorial layers, it is of particular interest also for the characterization of the presence of protective and consolidating treatments.
Compared to UV-induced visible fluorescence, for the reflected UV it is necessary to suppress the visible induced radiation and record only the part of UV reflected from the surface. In fact, the more superficial layers have the ability to absorb UV radiation more than the others. Its application is often used in a complementary and integrative way compared to induced fluorescence. In the study of the state of conservation, the use is exploited to verify the state of conservation as well as to map restoration areas carried out with particular material with little visible fluorescence but which exhibit a characteristic reflection or absorption potential in the UV.
Image in the visible
Image in long wave reflectography
(Source: Prof. Marco Gargano, Università degli Studi di Milano, Dipartimento di Fisica, sezione di Fisica per l’ambiente e i beni culturali)
Laser Doppler vibrometry: identifies areas of high mobility following an excitation of the structure under analysis using non-destructive techniques developed for the optimization of the signal-to-noise ratio. This technique is similar to the diagnostic method typically applied by restorers to identify areas of high mobility by manually striking the area under examination.
Passive and active infrared thermography capable of detecting thermal discontinuities due to surface and depth defects and the presence of humidity on walls and structures.
Thermographic relief (Source: Università politecnica delle Marche)
Laser Doppler Vibrometry relief
(Photo source: Prof. Paolo Castellini, Università Politecnica delle Marche (UNIVPM), Dipartimento di ingegneria industriale e scienze matematiche)