Revealing the binding medium of a Roman Egyptian painted mummy shroud

Ancient Egyptian painted artworks are usually understudied from an analytical point of view, due to their extremely fragile nature. Attention typically focuses on pigments since identification is possible with non-invasive techniques, while limited information is available in the literature regarding the organic binding media. Here successful determination of the binder of a Roman Egyptian painted mummy shroud (2nd–3rd century A.D.) achieved through the application of enzymatic digestion followed by matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) is reported. The high specificity and sensitivity of this analytical strategy not only allowed the identification of the binding medium as a mixture of two different plant gums but also allowed the discrimination of the different species sources, even though the organic material was present in very small amounts and subject to degradation. The results of this study represent the first analytical identification of the earliest use of locust bean gum as a paint binder material as well as the use of gum arabic from an Acacia species different from the well-known Acacia senegal. The precise identification of the organic binder is a great step forward in the understanding of the painting materials and techniques used in Roman Egypt, of which little is known. The result of this research opens new avenues of art historical and conservation investigation into the specific plant sources and types selected by artists and it has implications for future conservation treatment options.