Non-invasive FTIR study of mortar model samples: comparison among innovative and traditional techniques.

Mortars are among the most important building materials, with several different mineral phases as main components. The recipes used in the past come from local traditions, and a vast range of organic and inorganic additives could be included; unfortunately the recipes precise descriptions are not reported in historical sources, while the knowledge of the composition could be of major concern for technological information on the past and improvements in today’s conservation works. In recent years non-invasive portable instruments have played an increasing role in conservation science, especially for the analysis of paintings; on the contrary there are few articles on historical building materials. In this paper the performance of non-invasive external reflection infrared spectroscopy (ER-FTIR) is tested on model samples, prepared according to past recipes collected from historical manuals and the conservation best practices. The results are discussed and compared with the traditional analytical techniques, such as bench top transmission and attenuated total reflectance (ATR) infrared spectroscopy, with the contribution of powder X Ray diffraction (XRD). The influence of surface roughness on reflection infrared spectroscopy signals was considered and investigated too.