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Since the Hellenistic period, preparatory drawings known as sinopiae were employed as guidelines for mosaicists in creating mosaics. The sinopiae served as the basis for style and content, facilitating the placement of colored tesserae in the supporting mortar. The technology of the mosaic and pigments used reflect the capacity of the mosaic workshop and its master. This work explores a polychrome sinopia that was found under a Byzantine mosaic of an Armenian Chapel in Jerusalem, by a multi-analytical characterization of mineralogical and chemical properties. The composition of the pigments in the black and red areas of the sinopia include carbon black and red ochre, respectively, utilized in the fresco technique. Since colored tesserae are placed in wet mortar, it can be deduced that mosaicists worked together with painters during the executionary steps. This has corresponding implications for historical and artistic specializations at mosaic workshops, with deeper understanding of mosaic production processes. This research also highlights the importance of studying sinopiae under floor mosaics, which is a source of information on the pigments, paintings techniques, and the people who executed the work, all embedded in mortar which is well protected below the stone tesserae.
Asscher et al. (Mon,) studied this question.