Creating a Material Spectral Library for Plaster and Mortar Material Determination

Abstract

Historic object analysis and the knowledge of composition play an important role in restoration processes. Based on this information, restoration works are conducted. This paper introduces a non-invasive technique of plaster and mortar material decomposition using reflectance spectroscopy. For this purpose, a NIRQuest512-2,5 from Ocean Optics®/Ocean Insight®, is used to create a unique spectral library consisting of various materials. They were carefully selected to include those that were and still are commonly used for a plaster and mortar production. Each material of the spectral library was mapped in detail, verified using scanning electronic microscope (SEM) data, and the results were compared to a previously determined spectral signature. The new spectral library was then tested on 11 unknown plaster and mortar samples and verified using a scanning electronic microscope. It was found that reflectance spectroscopy provides a powerful tool for plaster and mortar material decomposition, although at the moment it cannot fully replace invasive techniques like chemical analyses or other invasive techniques. It provides relevant information that can be used for restoration works.

Spatial Validation of Spectral Unmixing Results: A Case Study of Venice City

“…In the flowchart, reference data utilized as input into a process is connected to it by a red arrow, whereas reference data used for the validation process are connected to it by a green arrow (Figure 1a). The selection of an accurate and complete reference spectral library is essential because the key to spectral unmixing is the determination of endmembers [4,24,29,30]. Some authors created a synthetic image exploiting these spectra and the reference map in order to test the proposed procedure and/or to validate endmember extraction [14,[31][32][33] and/or fractional abundance estimation (Figure 1b) [31,32,34,35].…”