Monitoring paint and primer samples using multispectral and hyperspectral imaging techniques

Multispectral imaging (MSI) and hyperspectral imaging (HSI) are non-invasive techniques that have been used to map and identify pigments, binders and retouches on work of arts. The spectral reflectance obtained from these techniques could be used for matching pigments. In this research we aimed to use these 2 techniques for monitoring the change of paint samples after they were systematically exposed by heat, moisture and light. Three primer samples, developed in our previous research, were applied on the acid and lignin free substrate, wet film thickness of 40 mu m, and left to dry for 30 days in a controlled condition. Five selected acrylic paints and 4 pastels, developed in accordance with Thai color names' dictionary, were similarly applied on the same type of substrate. All samples were exposed to moist heat at 50 degrees C and 60% RH up to 40 days. The rest of the paint samples were exposed to full spectrum of sunlight for 1, 10, 100, and 1000 h. The spectral reflectances of samples were recorded. In monitoring sample using MSI, the samples were captured with 10 bandwidths filters, 400-700 nm. The HSI, 400-1000 nm, with false color post process to images was employed to monitor the change of paint samples after exposing to UV of 1-50 h. The RGB and CIEXYZ data of MSI images were extracted and analysed. The colorimetric data could be used to examine the color change of paint samples. The lightness difference obtained from the MSI images showed distinct result in primers.