Medieval Illuminated Manuscript – Black Hours, Morgan MS 493, Pentecost, Folios 18v, c 1475-80. Morgan Library & Museum, New York (image in Public Domain).
Books of Hours, the most common example of Christian medieval illuminated manuscripts, are documents written by hand with illustrations, decorated initials and borders containing texts, prayers and psalms.
The ‘Hours’ refer to the Canonical Hours, periods of the day set apart for prayer and devotion, given by their names: matins, lauds, prime, tierce, sext, nones, vespers, and compline.
Many Books of Hours have gold, silver and lapis lazuli painted on papyrus, vellum, parchment or paper, and describe Christian religious content (although Islamic texts use the same techniques).
The images below show four Books of Hours from the Nationalmuseum of Sweden, which are displayed in an ArtRatio table, built using SPD Smartglass from Variguard.
We were pleased to see how the rich colours of the manuscripts are clearly portrayed by the smart glass, which by virtue of its flat spectral distribution does not alter the details and colours present on the manuscripts.
The Books of Hours exhibited in the ArtRatio display table include:-
We note that watercolours are classified as ‘moderately light sensitive’ by the CIE 157 Technical Report on Light Damage to Museum Collections.
It is thus significant that the smart glass in the OFF state reduces the light levels to close to 0 Lux.
Even if the object is viewed continuously during 8 hours per day, the object sits in complete darkness the remainder of the time, substantially reducing light exposure over the lifetime of the collection.
Reduced light exposure will reduce the risk of discolouration on watercolours.
Furthermore, gold is sensitive to changes in relative humidity, which is due to changes in temperature and this can result in tarnishing and discolouration of gold leaf.
Fluctuations in temperature are mitigated thanks to the smart glass, which rejects approx 50% of infrared (i.e. heat) contained in sunlight, thereby reducing fluctuations in humidity.
In this table, we used interior planks of 6mm thick Krion, an antistatic, anti-bacterial, extremely durable engineered solid surface from Porcelanosa in Spain, to minimise any risk of pollutants on the collection.
You can read more about KRION® on this Blog page.
Other conservation factors we designed in include:-