RESUMEN INGLES

The objective of this investigation is to develop a non-invasive method to characterize, measure, and predict the damage to pigments and binders in paintings, probably produced by the solar electromagnetic radiation (EMR) from the ultraviolet through the near infrared (220-850 nm).

Spectroscopy of reflection and absorption was used to analyze color samples exposed to solar radiation during the four hours of maximum irradiance for 120 days. The solar irradiance as well as that of artificial light sources was measured. These data were used to attempt predicting the damage produced by EMR to the color samples. The color change in each sample is analyzed as the variation in reflectivity and the energy absorption in the respective bands of the electromagnetic spectrum (EMS). The experiments showed important losses in color saturation. Spectroscopy analysis was performed to each color in its initial state, exposed under a filter, and exposed without filter. The measurements of these there conditions are compared and the differences in reflectivity are interpreted as grades of damage produced by the absorption of electromagnetic energy (EME). A spectrometer fitted with a cosine corrector (that collects radiation in a 180 degrees angle) was used to measure both solar irradiance and the sources of artificial illumination. To measure reflectivity and absorption of each color relative to Munsell’s White/9, a spectrometer with a coaxial fiber optic of 8 fibers that emit radiation from a Xenon light source and a central fiber optic that sends the color response to the spectrometer. Also, the effect of the radiation reduction of the filters was analyzed, showing that the damage is partially reduced.

The experimental data are analyzed with multivariate statistics and non linear mathematics avoiding the integration of the values obtained that, although simpler to explain, hide a large part of relevant information that is well shown with our technology.

The results of this investigation are: a) a method to characterize the damage to the paint based on the change in reflectivity of each band narrow of the EMS in the range analyzed (220-850 nanometers), b) quantification of damage based on the initial state of the samples and the exposed ones (with and without filter), c) prediction of damage by training mathematic non-linear models with the experimental data obtained, d) to show that some of the detected damages are related to the amount of energy absorbed by a given color in one or more of the regions of the analyzed EMS.

Finally, to illustrate the possible uses of this methodology the following applications were made by the author since 2006: 1)The ultraviolet radiation (UV) solar and artificial on the Musician Angels of the Metropolitan Cathedral of Valencia, 2) The light emissions of the Dior-Galiano archive in the city of Richelieu (France), 3) The light emissions of the Musée des Arts Décoratifs in Paris, 4)The ultraviolet radiation that bathes the frescoes of the house of Ariadna in Pompei, 5) A quantification of Munsell’s colorimetry.