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Heritage Science
Fig. 4 | Heritage Science

Fig. 4

From: Listening to laser light interactions with objects of art: a novel photoacoustic approach for diagnosis and monitoring of laser cleaning interventions

Fig. 4

Combined NLM and PA stratigraphic imaging and AC PA detection of hidden underdrawings in painting mock-ups. 1a Raw cross-sectional MPEF image of the mock-up. 1b Unmixed MPEF image of the overlying mastic layer. 1c Unmixed MPEF image of red lead paint layer. 1d PA image of underlying pencil sketch. 1e Composite MPEF and PA image (Scalebars Z: 100 μm; X: 1 mm). 1f Brightfield image of the region indicated with a white square in (1e) using near-UV light. The black dashed line represents the border of mastic layer. Both scalebars in Z and X dimensions correspond to 100 μm. 2a Brightfield view of a painting mock-up using an ultramarine blue paint layer. 2b Brightfield view of the underlying pencil sketch prior overpainting. 2c Recovered pencil underdrawing pattern through AC PA imaging. 2d NIR optical image of the painting sample recorded at 1050 nm. Similar data are presented for chromium green (2e–2h), vermillion (2i–2l) and zinc white (2m–2p) paints. All scalebars are equal to 5 mm. Figure adapted from [55] and [56]

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