This article discusses an informal study commissioned by the town council of Pinoso (in Alicante province, Spain) in 2011 requesting from ArtRatio an analysis of light levels incident on the Royal Town Charter, granted by King Ferdinand VII in 1826.
Ferdinand VII (known in Spanish as ‘Fernando VII de Borbón’) reigned briefly in 1808 before being tricked by his ally Napoleon into abdicating, leaving Napoleon’s brother Joseph Bonaparte to be installed as King of Spain.
This led to uprisings which began on the night of 2 May 1808 (immortalised by Francisco Goya’s painting ‘The Second of May 1808’) and marked the beginning of the Peninsular Wars, during which provisional Spanish juntas wrote the liberal Spanish Constitution of 1812 (nicknamed ‘La Pepa’).
When Ferdinand VII was eventually released by Napoleon, he was returned to the Spanish throne in 1813 and promptly overthrew the liberal 1812 Constitution and removed all monuments to it.
Pinoso was classified as a village dependent on the adjacent town of Monóvar (within the province of Alicante) but relinquished this dependence under the auspices of the Constitution of 1812 and was finally granted a Royal Town Charter by Ferdinand VII on 12 February 1826.
Figure 1 shows the original Royal Town Charter of 1826 in the offices of the mayor of Pinoso and was housed at that time in a polycarbonate vitrine measuring 50 x 35 x 7.5cm.
The book which contains the Charter has a backing of leather hide tied with ribbons and the Charter itself is made of paper and featuring a royal seal.
These materials would correspond to type-3 light sensitivity according to CIE Technical Report 157 and should be limited in light exposure to 150,000 lux-hours per year.
The illumination we measured with a Testo model 540 light meter was 213 lux on an October morning in Pinoso at around 10h45.
When we plugged the numbers into our spreadsheet (see below), we realised that the present solution permitted light exposure levels of over 600,000 lux-hours per year (almost 4 times the level recommended by the CIE:157 report).
The solution we proposed was composed of an electro-optic (‘smart’) glass vitrine, which would limit the exposure to 147,000 lux-hours per year (see below).
Our solution would constrain the Charter to light exposure only 46% of the time on display, which corresponds to 1380 hours per year (or 3.78 hours per day). This is possible due to the presence-driven activation of the electro-optic glass.
These results surprised staff at Pinoso Town Council and prompted an internal review of the ideal conditions under which to place this important document.
The spreadsheet in Fig. 2 compares light exposure of the same object (a) if placed behind a normal glass vitrine as opposed to (b) being placed behind an electro-optic (‘smart’) glass vitrine.
As you can see, the Smart Glass vitrine can limit the light exposure by activating only when triggered by presence, thereby allowing the object to be placed on public exhibition and yet minimising the damage from light.
As a result of our report, technical staff at Pinoso Town Council Archives department have confirmed that the Royal Charter has been replaced with a facsimile.
ArtRatio is in conversations with the client as to more cost-effective measures to limit light damage on the original document, with the aim of one day being able to exhibit this regional treasure to the people of Pinoso, Alicante.