It’s difficult for us to imagine a form of thought in which all material objects were considered symbols of spiritual truths or episodes of sacred history.
Yet, if we do not make this effort, medieval art remains largely incomprehensible.
KENNETH MCKENZIE CLARK
“The ancients already used to, but for great men or at least for men of some importance, to close the windows so that, without preventing the light, the winds or the cold would not enter; and this only in their baths, in the suds, in the stoves and in other hidden corners, closing the openings or areas with some transparent stones, such as agates, alabasters and some soft mixed marbles which draw to a yellowish color. But the moderns, who in greater numbers have glass furnaces, have made the windows of glass plates, similar to or imitating what the ancients made with stones. And with leads on each side, they have both tightened and firmed them; and with leads placed in the walls for this purpose, or indeed wooden frames, they have armed them as we will herto explain. And where at the beginning they’d used to make them simply of white, or sometimes even colored, glass, the architects have then imagined making mosaics and figures of those differently colored glasses and to use them as paintings. And the mastery has grown to such an extent that today we see this art of glass windows being brought to the perfection of the beautiful paintings made into tables… ”
Giorgio Vasari thus recounts the birth of painted glass windows, a refined art and at the same time a specific architectural means used over the centuries to protect sacred and profane environments.
The magic of stained glass windows arises from the polychrome play of the light passing through them and from the contrast, created inside the buildings, between light and darkness. These effects were obtained through a careful choice of color combinations: nothing was left to chance: precise laws determined the quantity of colors and their position within the panels.
The relationship between craftsmanship and religious function is highlighted by Vasari when, describing this art, he states that “…you wouldn’t think that it’s glass but rather something fallen from heaven, to serve as a consolation for men”. This close relationship between craftsmanship and religious mission implies that in Italy the art of glass often develops within convents and that glassmakers are given the suggestive name of “singers of the divine light”.
Since their invention, the fragility of stained glass windows has determined the need for immediate and continuous maintenance, almost always entrusted to workshops. Artesans often intervened in a clumsy way, carrying out dismemberments and mendings, careless and harmful cleanings, adding additional leads that disfigured the reading of the original drawings.
This careless maintenance probably originates from the fact that stained glass windows lost, over the centuries, the artistic and didactic importance they held during the medieval period, a period in which workshops played a fundamental role of mediation between religious and medieval culture. It also contributes to relegating the glass-art among the minor arts, for a long time.
Yet, the difficulty in finding the raw material, the skill required for its production, the secrecy with which the best secrets of the trade were kept, meant that this art was of great importance, even economically, in the Middle Ages. But in the Renaissance, stained glass windows had an increasingly marginal role in the decoration of sacred places, which perhaps relates also to the desire for works that lasted over time, such as frescoes. The impoverishment of the contents and a use of windows that was changing determined over the centuries a “levelling” of the art. Workshops, while continuing to make use of the well-kept secrets of the glass-art, lost the artistic and spiritual inspiration of the origins.
All these reasons entailed that for centuries the approach to the restoration of old stained glass windows has been limited exclusively to empirical techniques. There has been a lack of a broader awareness of the problems related to the restoration of art pieces, as developed for instance for paintings. The techniques for the restoration of glass artifacts are to these days a field in constant evolution, still requiring not only technical but also methodological and scientific in-depth studies.
Deterioration and restoration of stained glass windows, Paola Santopadre, Marco Verità in Vetrate, Amilcare Pizzi Editore, Milano 1991