ATR-FTIR spectroscopy as a way to identify natural protein-based materials, tortoiseshell and horn, from their protein-based imitation, galalith

This paper presents a new totally non-destructive methodology, for the identification of protein-based materials, tortoiseshell, horn and galalith, on heritage objects. Attenuated total reflexion (ATR) infrared spectroscopy combined to a deconvolution procedure of amide I band was performed to characterize the secondary structure of these materials and allows us to identify each material. The component at 1639 cm−1, attributed to the amide group involved in hydrated random-coil domains, allows us to distinguish horn from galalith and tortoiseshell. A second component, at 1614 cm−1, assigned to amide group involved in protein self-association, allows us to differentiate galalith and tortoiseshell. This differentiation is applicable to both raw and manufactured materials. Then, we applied our models to identify what unknown object was made of.