In the wall paintings of the church of San Saba (Rome), dating to the first half of the eighth century AD, Egyptian blue and lapis lazuli have been detected mixed together within the same pictorial layer. These are the oldest western paintings where lapis lazuli has been used as a blue pigment. This paper cites other instances of the use of lapis lazuli in ninth-century paintings and of Egyptian blue in late mediaeval paintings. Thus the dates for the commencement of the use of lapis lazuli and the discontinuation of Egyptian blue are significantly modified. Furthermore, the occurrence of both of these blue pigments in the San Saba wall paintings proves that the change from one to the other did not occur suddenly and that these two pigments were used concurrently in the same geographical context.
All Science Journal Classification (ASJC) codes
Gaetani, M. C., Santamaria, U., & Seccaroni, C. (2004). The use of Egyptian blue and lapis lazuli in the middle ages: The wall paintings of the San Saba church in Rome. Studies in Conservation, 49(1), 13 - 22. https://doi.org/10.1179/sic.2004.49.1.13