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
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 |
