Fig. 1. Results of 3D-μ-XRF depth profiling
(a): X-ray fluorescence sum spectrum obtained for analysis location 11;(b): Normalized elemental depth profiles for analysis location 11: 1, 2 and 3 represent the corresponding layers on the depth profiles

Fig. 2. μ-Raman spectra of red pigment from Baoding cliff statues at Dazu Rock Carving in Chongqing
(a): Red micro-area; (b): White micro-area

Fig. 3. μ-FTIR spectrum (identified as an oil) obtained for the ground layer of the panel painting

Fig. 4. μ-XANES spectra of As-containing pigment references and the painting
a: Potassium arsenate; b: Arsenic(Ⅲ) oxide; c: Arsenic(Ⅲ) sulfide; d₁—d₃: Selected micro-area of the painting

Fig. 5. Microfade test results for triplicate measurements for BWS1—3 and the freshly polished cross-section of Van Gogh’s geranium lake
The inset shows the autofluorescence of the cross-section immediately after fade testing