Volume 44, Issue 1 :: by Robert Jayson
For centuries, those of faith have admired the stained and art glass windows in houses of worship. The changing daylight streams through the glass, shifting colors and bringing life to the windows’ figures and forms while projecting plays of color and light throughout the interior spaces. The association of art glass with religious architecture has become a part of our cultural DNA, dating back centuries. During the Middle Ages, Christians and Muslims introduced large-scale, colored art glass windows, bringing light, color, beauty, and a heightened sense of the divine into houses of worship.
The Gothic stained glass style played the role of storyteller, offering Christian and secular scenes through intricate design and inspiring color and light. These windows shared the teachings of faith with all worshippers, whether literate or not. The clergy would use the windows to teach the gospel, ultimately elevating the art form as a symbol of the divine.
Natural light has always been symbolically equated with goodness and beauty, playing an important metaphorical role. In 12th-century France, the stained glass window enjoyed a growing preference among the religious community because of its exquisite relationship to daylight. In his memoirs, Abbot Suger of the Abbey of St. Denis equated “Divine Light” with the light shining through stained glass and gems. This philosophy of Divine Light reasoned that humans could spiritually experience God through natural light brought in through vivid, large-scale windows of art glass.
Perhaps this connection between the daylighting capabilities of art glass and the worshippers’ perceived spiritual experience can also be attributed to the “crown” and “cylinder” glass production methods themselves. The “imperfections” of original mouth-blown art glass, such as air bubbles, striations, and surface “movement,” contribute to the living quality considered so remarkable in antique glass. Sunlight is scattered and refracted as it penetrates the uneven glass surfaces, creating what appears to be a glow from within the glass itself.
Archeological evidence suggests that 7th-century Syrian craftsmen developed the mouth-blown “crown” glass method of window glass production. The molten glass was blown at the end of a blowpipe into a round ball, then opened at the far end and spun. The centrifugal force caused the glass to open into a disc shape. It was then attached to a solid iron “pontil” rod, removed from the blowpipe, reheated, and further spun until flat. Four centuries later, German glassblowers developed the “cylinder” method of producing mouth-blown window glass. Cylinder glass is still made today by Germany’s Glashütte Lamberts and by a couple of other specialized glass factories. The process begins with a ball of molten glass on the end of a blowpipe that is rhythmically blown and swung like a pendulum until an elongated pod-shape of the desired length and diameter is reached. The ends of the “pod” are cut from the glass to form a cylinder, which is then cooled, scored down its length, reheated, and flattened. The crown and cylinder methods of producing mouth-blown window glass allowed the creation of relatively large glass panels with superior transparency and a rainbow of colors.
Color has always been an essential element of glass. Medieval glaziers created a spectrum of hues through the addition of metallic salts and oxides. Added to the raw glass batch, gold produced a cranberry pink color; cobalt, blue; and copper-bearing minerals created greens and burgundy reds. Starting in the 13th century, glass masters began adding a secondary pigment to the surface of the glass in the form of a silver “stain,” producing golden ambers and expanding the range of color options. These ancient coloring techniques and formulas remain in use today.
Over time, art glass progressed from serving a minor decorative role in the marble and stone windows of early houses of worship to becoming a key material and aesthetic focus in Gothic, Gothic Revival, and modern spiritual architecture. Its development was prompted by the advent of the lead glazing technique in combination with crown and cylinder glassmaking. Acting as translucent walls, stained glass windows took the place of the murals and mosaics once common to religious edifices. Colored glass pieces were connected with lead channels, creating narrative panels that appeared like a mosaic of dark lines and colored light. The brilliant colors and lead lines became essential elements of Gothic architectural vocabulary.
According to the Art Glass Association, the earliest account of the lead glazing technique comes from the writings of the monk Theophilus in 1100 CE. Surprisingly few of the methods Theophilus described at the time have changed over the past nine centuries:
If you want to assemble simple windows, first mark out the dimension of their length and breadth on a wooden board, then draw scrollwork or anything else that pleases you, and select colors that are to be put in. Cut the glass and fit the pieces together… Enclose them with lead cames… and solder on both sides. Surround (the leaded glass panel) with a wooden frame strengthened with nails and set it up in the place where you wish.
After a brief decline during the Renaissance, stained glass enjoyed a comeback during the Gothic Revival of the mid-1800s. At this time, the Bolton Brothers left England for America, opened one of the country’s first stained glass studios, and crafted elaborate Gothic style windows for churches and other buildings. John LaFarge and Louis Comfort Tiffany further popularized the American art glass movement, combining their creativity with innovative fabrication techniques. After World War II, the Neo-Gothic movement called for architectural accuracy, encouraging the creation of numerous new Gothic art glass windows.
Today, architectural awareness of the uplifting properties of daylight, superior aesthetics, and color continues to keep mouth-blown art glass windows at the forefront of ecclesiastical architecture. Contemporary artists and glass studios continue to seek the “imperfections” characteristic of mouth-blown colored glass to enhance the “spiritual” luminescence of their religious projects. Lamberts art glass is among few modern building materials crafted through the original, centuries-old mouth-blown cylinder technique.
Currently, progress in the silicone lamination of art glass, supported by Lamberts’ research and development efforts, is allowing the creation of rich, painterly, lead-free glass windows of unprecedented size and visual complexity. The technique bonds the carefully cut colored glass pieces to a base glass, creating an elaborate mosaic of light and color, free of the traditional dark lead or copper lines. The base glass can be tempered or laminated in order to meet building safety codes.
Experimentation with art glass lamination started in 1910. One of the earliest successful silicone glass installations was realized in the late 1980s in England by Karl Heinz Traut of Derix Glasstudios. The first large-scale, domestically fabricated example of the modern silicone lamination technique in a religious application can be found in the Synagogue at Eldridge Street, New York City. Artist Kiki Smith and architect Deborah Gans joined forces to create the multilayered, 16-foot-diameter east window, fabricated by The Gil Studio in Brooklyn, New York. Silicone lamination is poised to enhance the role of art glass windows in modern houses of worship, possibly in the same way that leaded crown and cylinder glasses advanced the use of stained glass in medieval spiritual architecture.
Many windows in religious buildings today resemble the stained glass windows of ancient times. Although some are abstract works of art, they all focus on creating an atmosphere of light and color for the enhancement of the spiritual experience in houses of worship, much as the original Gothic stained glass windows did. This art form, developed nine centuries ago, continues to evolve and enjoy an everlasting place in modern religious art and architecture.