Abstract
The aim of the present study was to evaluate the relative attenuation of VIS, UV and NIR solar radiation through a large pond skylight into the interior of the l’Almoina Archaeological Museum (Valencia, Spain), and to determine how relative attenuation varied throughout the year and time of day. Measurements were taken at 9:00 a.m., 12:00 p.m. and 3:00 p.m. during July 2019 and January 2020. Relative attenuation values were obtained from the measurement of spectral irradiance in the exterior and at different points in the interior by means of two Ocean Optics spectrometers: HR4000CG-UV-NIR for VIS (400–700 nm) and NIR (700–1000 nm) bands, and FLAME-S-UV-VIS for UV-A (280–315 nm) and UV-A (315–400 nm) bands. The central points of the skylight had relative attenuation at 520 nm, reaching a value of 50% in summer at noon and 38% in the afternoon. At noon in winter, there were two relative attenuation peaks above 33% at 520 nm and at 900 nm. For mean relative attenuation, in the UVB range, the highest relative attenuation (20%) was inside the ruins in the morning in both summer and winter, and the UVA band relative attenuation was quite constant throughout the museum, but lower than that of the UVB band, in the range 0–3%.
Highlights
The present study aimed to evaluate the relative attenuation of solar radiation in the interior of the l’Almoina through the water-covered skylight, for visible light (VIS), ultraviolet rays (UV) and NIR, and to determine how relative attenuation varies over time, throughout the day and the year; how it is distributed in space; and to what extent it is affected by the presence of the sheet of water over the glass, all this taking into account that the l’Almoina is a museum and the skylight was designed mainly for lighting and visual relationships, but not for the ideal environmental conditions for the conservation of the archaeological remains
This study of the relative attenuation of the UVB band from 300 nm and the UVA, VIS and NIR bands through the skylight indicates that the highest relative attenuation occurs in the VIS band in both seasons and in the NIR band (80%) in winter
Our results are in agreement with those of Tuchinda et al [25], who found that clear glass allows up to 90% of VIS light to pass through, depending on its thickness, and with those of Li et al [26], who found relative attenuations higher than 78% in the VIS region of a quartz glass slab
Summary
The preventive conservation and maintenance of archaeological sites is one of the requirements of the main international charters on the protection of archaeological heritage [1,2,3,4].Protection against excessive light radiation and ultraviolet rays (UV), in particular, is one of the factors in the proper conservation of cultural assets [5] (pp. 158–164).prolonged exposure to visible light (VIS) is known to cause pigment discoloration, and UV causes yellowing and disintegration of certain materials, while the infrared band (IR) causes warming of the surface of objects that can eventually lead to thermal deterioration [6].The case study described here is within an archaeological site in Valencia (Spain) containing the remains of different historical epochs, the oldest of which dates back to the foundation of the city in the Roman Republic period [7,8]. The preventive conservation and maintenance of archaeological sites is one of the requirements of the main international charters on the protection of archaeological heritage [1,2,3,4]. Protection against excessive light radiation and ultraviolet rays (UV), in particular, is one of the factors in the proper conservation of cultural assets [5] The site is next to two of the most representative of the city’s religious buildings: Cathedral and the Basilica of Our. Lady of the Forsaken. A museum was built in 2006 to preserve the site, on which a public square was erected, including a large skylight of about 300 square meters
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