Skip to main content

Advertisement

Table 1 Summary of FT-IR, OCT and LIF data obtained after the laser cleaning tests (series C—Fig. 1a, e) performed on the Floral painting

From: Laser cleaning of paintings: in situ optimization of operative parameters through non-invasive assessment by optical coherence tomography (OCT), reflection FT-IR spectroscopy and laser induced fluorescence spectroscopy (LIF)

Area F = fluence (J/cm2) N = number of pulses Layer examined with FT-IR after cleaning Cross-section and changes in structure of layers as seen with OCT after cleaning (OCT tomograms cover an area of 2 × 0.5 mm2, bars represent 200 μm in both directions) Average thickness of removed material (μm) Layer examined with LIF after cleaning
C1a 1.1 30 Probably paint layer (noisy spectrum) Wax and uppermost varnish removed, second upper varnish mostly removed, overpaint mostly removed; increased surface roughness 65 ± 21 The band at 473 ± 5 nm is reduced in intensity and red shifted to 483 ± 5 nm after cleaning A new band appears at 610 ± 5 nm
C1b 1.1 20 Probably paint layer (noisy spectrum) Wax and uppermost varnish removed, second upper varnish mostly removed, overpaint mostly removed; increased surface roughness 69 ± 18
C2a 0.9 50 Probably paint layer (noisy spectrum) Wax and two upper varnishes removed, overpaint mostly left; increased surface roughness 55 ± 14
C2b 0.9 40 Probably paint layer (noisy spectrum)
C3a 0.9 20 Probably paint layer Wax and two upper varnishes almost removed, overpaint not removed; increased surface roughness 42 ± 12
C3b 0.9 10 Natural varnish Wax and uppermost varnish removed, second upper varnish reduced, overpaint intact 30 ± 6 Emission intensity is increased after laser irradiation. No other changes are observed
C4 0.7 25 Natural varnish Wax and uppermost varnish partially removed, second upper varnish and overpaint not removed 19 ± 5
C5 0.7 46 Probably paint layer (noisy spectrum) Wax and uppermost varnish removed, second upper varnish locally left, overpaint not removed; increased surface roughness 34 ± 10 The main band at 473 ± 5 nm is reduced in intensity and red shifted to 483 ± 5 nm after cleaning A new band appears at 610 ± 5 nm