Fig. 6

Photo images (a, b) and Raman intensity images (c–f) collected from the paint distributed on a gyprock surface. In a, the squared area of 10 μm × 10 μm is zoomed in as b and scanned. Raman spectra were collected under an objective lens of 100×, integration time of 1 s for each pixel of 0.33 μm × 0.33 μm (to create a spectrum matrix of 30 × 30). The intensity image (c) map acrylic at ~ 2910 cm⁻¹ (d) and colourant at ~ 440 cm⁻¹ (e), respectively, as marked under the image, after 20% colour off-setting. d, e Re-construct (c) including mapping acrylic at ~ 2910 cm⁻¹ (d) and colourant at ~ 440 cm⁻¹ (e) using contour lines, respectively. f Merges (d, e) after re-construction