Fading and showing mechanisms of ancient color relics based on light scattering induced by particles.

Fading and showing mechanisms of ancient color paintings based on light scattering induced by particles were proposed. To confirm the mechanisms, simulated and application experiments were carried out to restore an ancient blurred color painting. Loading TiO particles (500-1000 nm) onto a piece of colored paper could result in blurring of the color of the paper, which is attributed to light scattering caused by air voids between the particles. Filling air voids with ionic liquid (a non-volatile solution with a high refractive index) could highlight the color by reducing scattering. These results were experimentally testified by the combination of a fluorescence probe and multi-angle reflectance spectra, in which scattering decreased the incident optical path in the painting layer while the incident optical path was increased by filling the air voids with ionic liquid. As a practical example, the proposed method was applied to highlight an ancient Chinese painting with blurred color. This investigation is very useful to restore faded color paintings.