2.2.5. MA-XRF

The elemental mapping of *Landscape in Switzerland* was conducted with the M6 Jetstream from Bruker Nano GmbH. The instrument's measuring head is equipped with a Rh-target microfocus X-ray tube (30 W, maximum voltage of 50 kV, maximum current of 0.6 mA), and a 30 mm2 active area XFlash Silicon Drift Detector (energy resolution of <145 eV for Mn-Kα). The measuring head is mounted on an X-Y-Z motorised stage with a maximum travel range of 800 × 600 × 90 mm. The instrument offers an adjustable spot size from 100 μm to approximately 500 μm [18]. The paintings' elemental distribution maps were acquired with a dwell time of 10 ms/pixel, a pixel size of 300 μm, and an anode current of 599 μA. The data were collected and analysed with the Bruker's M6 software.

#### 2.2.6. FE-SEM-EDS

The paint samples' cross-sections were mounted on carbon tapes and examined with a Hitachi SU5000 FE-SEM coupled with Bruker XFlash® 6/60 EDS. The SEM, backscattered electron mode (BSE) was operated with 60 Pa chamber pressure, accelerating voltage of 20 kV, 50–60 intensity spot and a working distance of 10 mm. The acquisition of data and processing were performed using the Bruker ESPIRIT 2.0 software.

#### 2.2.7. ATR-FTIR

ATR-FTIR analyses were performed using a Bruker Hyperion 3000 FTIR microscope equipped with a mid-band MCT detector, coupled to a Vertex 80 FTIR spectrometer. For each sample, 64 scans were recorded in the spectral range of 4000–600 cm−<sup>1</sup> and resolution of 4 cm<sup>−</sup>1. The spectra were interpreted with Bruker Opus 7.5 software.
