Since 2004, scientific research on the damaged Giant Buddha statues and Buddhist paintings in Bamiyan, Afghanistan, has been conducted at various laboratories and large-scale facilities using mass-spectrometry techniques (GC-MS, LC-MS, LC-MS/MS, nano-LC/ESI-MS/MS), ELISA, and synchrotron-based micro-analyses) in parallel to conservation intervention. Studies on samples from these cultural heritage objects have shown that each is composed of a polychromatic multilayered structure with sizing layers, ground layers, painted layers, and glaze. The carefully produced complex multilayered structures were examined using optical microscopy (visible and UV light) as well as synchrotron-based infrared microscopy, both of which revealed various organic and inorganic components in each layer. High sensitivity bulk MS and ELISA methods were used to further identify details regarding organic materials, such as fatty acids and collagens, and these results suggest different vegetable oils and animal species of glues. For example, cow milk casein and cow skin glue were identified in the Eastern Giant Buddha, suggesting that casein was used as a sizing agent and the cow skin glue as a binder for painting. The wall paintings from Cave N(a) (mid-7th century AD) were found to have horse glue used as sizing and drying oil (poppyseed/walnuts/perilla oils) as a binding media. The paintings’ complex structures and their organic and inorganic materials were fully understood using both imaging and bulk methods, and thus, these methods help to reconstruct historical wall painting techniques in full.

This paper evaluates museum lighting sources by proposing indices of color variety perceivable in artworks under illumination. We adopt three types of white LED with highRa values of 90, 96 (excited by blue ray, B-LED), and 97 (excited by purple ray, P-LED) where correlated color temperatures (CCTs) are 3000K and 4000K, and we use some other supplementary LEDs. These LEDs are applied to two groups of oil paintings. The first depicts the same hydrangea motif drawn under two different lightings, and the second is two masterpieces in the National Museum of Western Art, Tokyo. We propose and test three indices of color variety. Two are color standard deviations σ³ ₇₆and σ³ ₀₀of CIELAB color space measured by CIE1976 color differenceΔE* _ab and CIEDE2000 color differenceΔE ₀₀, respectively. The third index is color diversitySobtained via color entropy of an artwork’s probability distribution in the CIELAB color space discretized withΔE ₀₀. A color reference chart and a numerical model of color distribution are preliminarily examined to show basic properties of the indices. Experimental results of the paintings reveal the effectiveness of σ³ ₀₀andSand show that P-LEDs may yield higher color variety than B-LEDs withRa values nearly equivalent to those of P-LEDs with considerable certainty. We discuss similarity between the properties of σ³ ₀₀and those ofSfrom the viewpoint of distribution bias in the CIELAB color space and mention a kind of correlation between the similarity andRa value.