| Περίληψη |
During the elaboration of the current study, the development of an innovative, non-destructive,
detection technique for mural underdrawings was presented, based on the principles of PA
microscopy. The method is based on the absorption of IR radiation by the material used for the
underdrawing, which leads to the creation of a wave pressure that results in the creation of an
ultrasonic wave, which is detected by the transducer. The raw signal is filtered and saved in a
computer with a view to the creation of an image. It is important to mention the fact that the current
work is a proof of concept study, as the mock-ups used during the measurements represent ideal
cases of mural samples. Their substrate is very homogeneous and the sketches are drawn with
graphite pencil, which is known from previous studies to have better absorbing traits at 1064 nm in
comparison to carbon, which is the main material used for the underdrawings of murals. Better
absorption leads to the production of ultrasound waves with higher amplitudes, which is translated
as greater contrast in the constructed image. Nevertheless, the results of the experiment are very
promising and the method has demonstrated the excellent capabilities of PAI to uncover hidden
content in a mural sample consisting of different pigments, or even, gypsum. Lastly, we should report
the fact that the specific technique is relatively low-cost and it does require a very sophisticated or
complex configuration. We hope that with proper modifications and enhancements, this
experimental set-up could become a useful tool for art conservators and restorers.
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Detecting hidden sketch drawings and fresco layers using a novel, photoacoustic, diagnostic approach
