Degradation of Lead-based Pigments by Atmospheric Environment

Abstract

We examined degradation characteristics of lead based pigments(White lead, Red lead, Litharge) according to atmospheric environmet condition, for example UV, atmospheric gas(CO 2 , NO 2 ) and soluble salt. Painted samples not changed material compositions but were occured the color change(ΔE 4~31) after exposed UV irradiation. All samples were not affected by CO 2 gas not only color but chemical composition. However, samples were remarkably changed color exposed NO 2 gas and it was formed secondary product like as lead nitrate. Such as red lead and white lead samples' color difference were ΔE 2 and ΔE 10 respectively and became dark, along with litharge became bright and color difference was ΔE 5 after react with NO 2 gas. It confirm that NO 2 was influential factor than CO 2 in the case of same concentration. Furthermore salt spray test was taken to figure out soluble salt influence in fine dust. The result showed noticeable color change and secondary product was formed on samples' surface. The glue film peeled off or hole, and color changed around the secondary products. After salt spray, XRD pattern showed decrease peak intensity and lower crystalinity. As a result of salt spray test, white lead was formed new product litharge and litharge was formed litharge and minium. According to the results, influential atmospheric factors for conservation of paint pigments were UV, NO 2 , soluble salt, and litharge was most weakness throughout lead base pigments.

Raman spectroscopy of yellow organic pigments of large Korean Buddhist paintings from the late Joseon dynasty (17th–19th centuries)

“…However, the tonality of yellow was adjusted using white pigment to create various shades of yellow. Lead‐based white pigments are the most commonly used owing to their low levels of oil absorption, high activity, ability to form hard‐colored layers, and good coloring capacities 51 . Challenges associated with p‐XRF include the small analysis area and the absence of chromophoric elements in organic compounds.…”

“…Lead-based white pigments are the most commonly used owing to their low F G U R E 7 Raman spectra of the specimens (the number of each spectrum indicates the delaminated specimen collection point shown in Figure 2) levels of oil absorption, high activity, ability to form hard-colored layers, and good coloring capacities. 51 Challenges associated with p-XRF include the small area and the absence of chromophoric elements in organic compounds. Thus, the use of Raman spectroscopy to overcome the limitations of in situ non-invasive analysis facilitates the identification of organic pigments.…”