Near infrared (NIR) spectroscopy: a potential new means of assessing multi-phase earth-built heritage

Abstract

Earth-built structures were historically very common in Scotland. As building techniques have changed, the number of standing earth buildings has reduced. Now the few earth buildings that remain are significant testaments to a lost craft tradition. Understanding the composition of earthen materials used in construction enables better decision making in conservation. Here, we utilise near infrared (NIR) spectroscopy as a portable, non-destructive tool to assess the mixed inorganic and organic matrix from earth-built structures and experimental comparators. NIR is shown to be able to distinguish clearly between clay-rich blocks of different origin. Admixtures of aggregates such as topsoil, gravel and straw have a significant impact on the spectral data collected. This technique has the potential to better inform repairs and conservation works on historic earth-built buildings.