Hyperspectral imaging as powerful technique for evaluating the stability of Tattoo Wall®

The aim of this work is to present the utilization of hyperspectral imaging to evaluate the stability of Tattoo Wall®, in respect of simulated solar radiation and extreme humidity conditions, for a possible use in the restoration field. Tattoo Wall® is a new and never investigated decorative technique involving transferring digital images on wall surfaces through a transfer paper with solvent-based ink and fixative. This technology shows high stability, but the long-term degradation is not well defined. In order to test the possibility of using Tattoo Wall® in the field of restoration of cultural heritage, Hyperspectral imaging in the visible and short-wave infrared range was applied on samples prepared with different ground mortars and protective layers. Hyperspectral imaging was used before and after artificial ageing procedure, performed under controlled conditions, simulating solar radiation and high values of relative humidity. Data were treated and elaborated in order to evaluate the sensitivity of the proposed technique in order to identify the variations on paint layers, induced by photo-degradation and humidity, before they could be detected by eye. Furthermore, a supervised classification method to evaluate the possibility of the Tattoo Wall® surface changes monitoring was successfully applied adopting a multivariate approach.