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)
Abstract:
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.