Detection of the TiO2 Concentration in the Protective Coatings for the Cultural Heritage by Means of Hyperspectral Data

Antonio Costanzo,Silvestro Antonio Ruffolo,Maria Fabrizia Buongiorno,Sergio Falcone,Carmelo La Piana,Massimo Musacchio,Mauro Francesco La Russa,Donatella Ebolese

doi:10.3390/su13010092

Antonio Costanzo, Silvestro Antonio Ruffolo + Show 6 more

Open Access

https://doi.org/10.3390/su13010092

Copy DOI

Abstract

Nanotechnology-based materials are currently being tested in the protection of cultural heritage: ethyl silicate or silica nanoparticles dispersed in aqueous colloidal suspensions mixed with titanium dioxide are used as a coating for stone materials. These coatings can play a key role against the degradation of stone materials, due to the deposit of organic matter and other contaminants on the substrate, a phenomenon that produces a greater risk for the monuments in urban areas because of the increasing atmospheric pollution. However, during the application phase, it is important to evaluate the amount of titanium dioxide in the coatings on the substrate, as it can produce a coverage effect on the asset. In this work, we present the hyperspectral data obtained through a field spectroradiometer on samples of different stone materials, which have been prepared in laboratory with an increasing weight percentage of titanium dioxide from 0 to 8 wt%. The data showed spectral signatures dependent on the content of titanium dioxide in the wavelength range 350–400 nm. Afterwards, blind tests were performed on other samples in order to evaluate the reliability of these measurements in detecting the unknown weight percentage of titanium dioxide. Moreover, an investigation was also performed on a test application of nanoparticle coatings on a stone statue located in a coastal town in Calabria (southern Italy). The results showed that the surveys can be useful for verifying the phase of application of the coating on cultural heritage structures; however, they could also be used to check the state of the coated stone directly exposed over time to atmospheric, biological and chemical agents.

Highlights

Preserving memories means taking care of our past in looking to our future
This behavior is strongly linked to the weight percentage of titanium dioxide added in the coating; by analyzing the spectral signature of the titanium dioxide provided in the ASTER spectral library [28] and graphically represented in Figure 6, it can be noted there was a high slope in the wavelength range between 350 and 400 nm, with a strong decrease of the reflectance moving towards the ultraviolet range
Many structures of cultural heritage significance, especially those located in urban environments, are often exposed to negative effects due to high pollution and concentrations of fine particulate

Summary

Introduction

Preserving memories means taking care of our past in looking to our future. Conserving the identity, in its huge variety, of our world cultural heritage will ensure solid roots are maintained for future generations. Cultural heritage encompasses a vast area and includes different types of historical and artistic goods, tangibles and intangibles. Each one of these requires a particular preservation procedure, often customized in relation to the environment with a holistic view (e.g., [1]). There are many components of the urban landscapes which are often subjected to negative effects due to interaction with the surrounding environment. In these landscapes, historical buildings and monuments, often built in natural and artificial stone materials, are among the more exposed elements [2,3,4]. Pollution and high concentrations of fine particulates, typical of the urban environment, play a role in accelerator the deterioration

Methods

Results

Conclusion