Plasters from Jewish ritual purification baths in Late Hellenistic–Early Roman Palestine: composition, production areas, and anthropogenic residues

We report on the compositions of plaster samples from five Late Hellenistic–Early Roman (ca. 1st c. BCE–2nd c. CE) archeological sites in Israel (Horvat ‘Ethri, Sepphoris, Gamla, Keren Naftali, and Yodefat), analyzed via wavelength-dispersive X-ray fluorescence spectrometry (WD-XRF), inductively coupled plasma mass spectrometry (ICP-MS), petrographic and scanning electron microscopy (SEM-EDS). Altogether 54 samples, including plaster from 13 stepped pools (conventionally identified as Jewish ritual baths) and potential raw materials, were analyzed to characterize the plasters’ compositions and technologies, geochemical concentrations of the plaster mixtures and the binder and aggregate materials. Furthermore, we explored potential local plaster production at the sites and anthropogenic enrichment on the plastered surfaces. Non-invasive on-site pXRF analysis was also carried out. Plaster characteristics support our hypothesis of local plaster production, but significant inter-site correlation of plaster technologies suggests intercommunal knowledge-sharing or control of the plaster industry. Chemical residue anomalies detected on some of the studied surfaces indicate alternative use strategies for some of the stepped pools.