Lammerite as a Degradation Product of Emerald Green: Scientific Studies on a Rural Persian Wall Painting

• Published in: Studies in conservation Vol. 63; no. 7; pp. 391 - 402
• Main Authors: Holakooei, Parviz, Karimy, Amir-Hossein, Nafisi, Golriz
• Format: Journal Article
• Language: English
• Published: Routledge 03-10-2018; Taylor & Francis, Ltd
• Subjects: arsenic migration; Emerald green; glushinskite; huntite; lammerite; ORIGINAL RESEARCH OR TREATMENT PAPER
• ISSN: 0039-3630; 2047-0584
• DOI: 10.1080/00393630.2017.1419658

Pigments on a figurative wall painting in Poudeh village, central Iran, were analysed by micro X-ray fluorescence spectrometry, micro Raman spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectrometry, micro Fourier transform infrared spectroscopy, X-ray diffractometry, and polarised light microscopy. Red lead, ultramarine blue, chrome yellow, brass powder, white huntite, and lammerite (Cu
3
(AsO
4
)
2
) were identified as red, blue, yellow, golden, white, and green pigments, respectively, while gypsum and barite were used as extender. In addition, glushinskite (MgC
2
O
4
·2H
2
O) was identified as a deterioration product of white huntite. Moreover, several analytical studies suggested that lammerite was a degradation product of emerald green (Cu(CH
3
COO)
2
·3Cu(AsO
2
)
2
) originally used as green pigment in the painting. The formation of lammerite is suggested to be due to the migration of arsenic throughout the paint layer. Based on the pigments identified, the wall painting is dated from the mid-nineteenth century to the mid-twentieth century.