Ancient Mortars and Plasters

Mortars and plasters are complex artificial stone materials, whose improvement and diffusion has been strongly influenced by the birth of pyrotechnology. Their chemical, mineralogical, and petrographic composition depends on the locally available raw materials and on the technological know-how of the workers who produced them. An in-depth study of ancient mortars and plasters can help archaeologists to solve various issues such as the provenance of the raw materials from which they were produced and the identification of the construction phases of ancient architectural structures. Several kinds of raw material were used for making ancient mortars and plasters: various types of rocks, which were required for producing aggregates and binders; and organic materials, which were sometimes added to the mixture as additives. Their compositional characterization requires a multianalytical approach, which must include optical microscopy (OM) under transmitted polarized light.