Stained glasses art: history and techniques


TThe stained glasses art, as assembly of coloured glass sheets connected by lead rods, is bound up with architecture, and didn’t really change since the Rinascimento and even since the Middle Ages. By the quality of the light and colour that it brings into a room, it allows to create particular atmospheres. The glasses, having more or less three millimeters thickness, are painted and then cooked, and are sometimes assembled to form compositions of various shapes and sizes, on whatever subjects. By selecting the light according to the thickness of painting, the colours, the materials, stained glasses obtain very varied and rich perspective effects, allowing to emphasize all kinds of scenes and characters. They are an ideal support for religious art, especially at the moment when the churches are modifying their architecture in favour of light, with the new elongated opening and the rose-windows on their façades.

Glass exists in a state of nature, as obsidian(natural glass made by rocks’ transformation during volcanic eruptions), and was for man of some thousand years-long use, to make tools, weapons and jewels. White artificial glass is attested in Mesopotamia, Egypt and other Eastern countries, approximately three thousand years before our era. Still opaque, the glass gradually colours, first in green and then in blue. The furnaces’ improvement permitting stronger temperatures, the glass which they cook comes out thinner, and translucent. It allows to copy gems, and objects made of hollow glass begin to appear: vases, bottles, pots… Romans are first in using glass to protect their houses from climatic variations. They make their glass “on board”, which means that it is poured and then laid on a plane wooden support or a bed of sand. Its oldest specimens were found in Pompei.

During the first century before our era, probably in Syria, does the blowed glass appear, obtained with the help of a cane, and so do the first transparent glasses, in Phenicy. That was the starting point of a trade of glass vessels on a large scale, everywhere in the Mediterranean region. Colourless glass, obtained by using manganese in the initial paste, is propagated since the third century of our era.

Balsam containers - blowed glass - Siria - II century – Height: 7 to 17 cms
Source : Musée International de la parfumerie de Grasse

We don’t know precisely when the stained glass took a distinction from the simple glass panels. Medieval texts do mention the "glasses of innumerable colours", but they don’t give us more details, except that those glasses are to be found essentially in churches, probably set in wood or putty. Both archeology and documentation left us only few reliable news. We just know that the stained glass existed already in Merovingians’ and then Carolingians’ era, coloured already, and undoubtedly figurative. In that period two different blowing techniques appear producing flat glass: "in crown" (an opened and centrally spreaded cylindrical bubble) and "at sleeve" (an oblong bubble opened laterally to obtain a flat rectangle). The oldest stained glasses which were found attest that very elaborated techniques were in use even in Middle Ages. These ancient stained glasses are manufactured coloured panels of glass, already maintained by grooved lead, welded to make the whole homogeneous. At the very beginning, decorations are carried out in brown or black colours only, assembled in simple rectangular or circular compositions. They were framed in iron or wood, following nearly the same techniques that we use today.

The level attained by those techniques around the year 1100, allows such a good control in manufacturing stained glasses, that it can be admired after many centuries for the oldest of them, still visible today in the Augsburg Cathedral in Germany. Now one of principal means of artistical expression, the “vitrail” characterizes the Gothic religious art, whose architectural challenge is to release larger surfaces to be glazed. It is a big change from the Romanic churches, which used more white glasses, in order to supply the most of light in buildings whose thick walls offered scanty openings.

Its growing iconographic abundance, in erudition as in subjects’ complexity (Old and New Testameent, the parallels, the holy Trinity, Christ double nature…) and in didactic representation, will be disapproved by the Church reforming movements (cistercians, franciscans…). They consider excessive the preciosity reached by the stained glasses, and seek to simplify to the utmost their colours and topics. The major part of the Church considers possible, as abbé Suger wrote in placing an order in 1144 for the royal Saint-Denis basilica stained glasses, "to direct the thought of the believers by material means towards the incorporeal". The narrative scenes increase in quantity and quality. The bottom ranges of churches’ windows describes the details of Christ’s and Saints’ lives episodes. The highest windows give larger representations of the principal and recognizable protagonists of holy history. Large rose-windows embellish the most important churches. But even if now widespread in Europe, the “vitraux” have no common reading mode for their contents, each one using its own expressing code.

The colours diversify and multiply, opening a broad artistic field to the masters in glass-making and painting. In the colours’ range, one asks the various blue to be much deeper, the red sharper; the green varieties become numerous, while the yellows, used for those mixtures, lose their importance in their pure appearance. This new variety of blowed glasses, allowing such important innovations, considerably enrichs the settings. In XIV century, they benefits of a three colours association ( black, brown and "sepia") and of a wide range of silver-salts which offer special transparencies, beautifully saturated with various yellow shades. In XV century the "violet", results from plating the red glass on the blue one, and the “sanguine” appears. The laws of “perspective” and the "damask"(a regularly repeating decoration of Eastern origin) come in fashion.

With the end of Middle Ages and the beginning of the Rinascimento, a different stained glass art appears, more complex and refined. The sanguine colour (also known as "flesh pink") is now popular, as well as translucent enamels (blue, green, violet). The vogue is for the "Italian style" scenes, and a new realism in characters and landscapes. At the service of those more complex demands in representation, the glass painting techniques also increase their precision and complexity, e. g. By juxtaposing several colours on a same sheet of glass, to give a higher degree of accuracy, and increasingly subtle nuances. At this point of complexity and results, the glass artists often put their signature on these artworks.

The XVII and XVIII centuries’ period, on the contrary, is unproductive for stained glasses. Baroque architecture, as the neo-classical, seeking more marked effects and dramatization, need the maximum of light. New techniques exist now to produce larger glass sheets for larger and more transparent windows, opening palaces, houses and churches onto the external world. The stained glass loses its importance.

Only during the romantic XIX century will the nostalgic craftsmen re-discover the ancient masters’texts, referring to the “vitrail” tradition to use again its techniques, at the same time fitting the old manufacturing processes in the brand new methods of industrialised production. This new trend gives birth to real enterprises, capable of real works of art issued on request in the best traditional way, as also to sell, on a large scale from catalogues, ready-made decorative stained glasses.