Creating a Material Spectral Library for Plaster and Mortar Material Determination.

Understanding the composition of historic materials is essential for conservation and restoration. Prior research has shown that chemical and physical properties of materials influence restoration choices. However, invasive methods can damage fragile objects. This gap motivated the search for non-invasive alternatives. No prior work had resolved how to reliably identify plaster and mortar without disturbing the material. Existing methods rely on chemical analysis, which is not always feasible. That uncertainty drove the development of new optical techniques. Reflectance spectroscopy was already known to detect surface composition. But its use in historic material identification remained unexplored.

The goal was to develop a non-invasive method for identifying plaster and mortar compositions. The study aimed to create a spectral library of common materials used in these substances. This would allow for quick and non-damaging analysis of historic objects. The motivation was to support restoration efforts without compromising the integrity of artifacts. The researchers propose using reflectance spectroscopy as a primary tool. They wanted to test if this method could reliably distinguish materials. The study also sought to compare spectral results with SEM data. This would validate the accuracy of the non-invasive approach.

The team used a NIRQuest512-2,5 spectrometer from Ocean Optics®/Ocean Insight®. They collected reflectance data from materials commonly used in plaster and mortar. Each material was selected based on historical and current usage patterns. The spectral signatures were mapped and compared to SEM results. The researchers verified each material's spectral profile against known data. They built a database of these profiles for future reference. The library was then tested on 11 unknown samples. Scanning electron microscopy was used to confirm the results.

The spectral library successfully identified materials in the unknown samples. Reflectance spectroscopy matched SEM results in most cases. The method showed high accuracy in detecting common plaster and mortar components. However, some materials could not be fully distinguished using this technique. The researchers found that while non-invasive, the method has limitations. It cannot replace invasive techniques in all cases. The spectral data provided enough detail for restoration planning. The results suggest that this approach is a valuable addition to current methods.

The authors propose that reflectance spectroscopy is a useful tool for material identification. It provides relevant data for restoration without damaging the object. The spectral library offers a practical resource for analyzing historic materials. However, the method cannot fully replace invasive techniques. The researchers suggest using it in combination with other methods. The findings support the use of non-invasive tools in conservation. The study confirms the potential of optical methods in material analysis. It highlights the need for further refinement of spectral libraries.