Koochakzaei, Alireza; Achachluei, Mohsen Mohammadi; “Red stains on archaeological leather: degradation characteristics of a shoe from the 11th–13th centuries (Seljuk period, Iran)”, Journal of the American Institute for Conservation 54(1) (2015) 45–56.
DOI: 10.1179/1945233014Y.0000000033 (Maney Online, restricted access)
In 2006 several valuable leather objects were found during archaeological excavation of Ghalee-Kooh-i Ghaen (a historic stronghold from the Seljuk period, 11th–13th centuries) in the South Khorasan province of Iran. When examined after 5 years, there were red stains on the remnants of a shoe with poor strength and powdery surface similar to red rot decay. Since red rot is more common in manufactured leathers from the mid-19th century, the purpose of this research was to clarify the structural features and degradation factors responsible for red stains on the shoe. Chemical spot tests, isolation and identification of fungi, pH measurements, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy were used to achieve these aims. These measurement results corresponded to lime depilation, tanning with alum and vegetable tannins, and the possible use of CuSO4 as a preservative of skin in leather-making process. Cladosporium sp. and Penicillium sp. were isolated from the shoe, but Trichophyton sp. was characterized as the main biodeterioration factor. Fourier transform infrared spectroscopy and pH measurements indicated hydrolysis and acidic degradation of the leather. The characteristics of the red stains were similar to those exhibited by red rot. Therefore, archaeological leathers tanned with alum and vegetable tannins may be exposed to acidic degradation like red rot decay.