November 2012 Print

Perspective on Stained Glass

Zuzana Killam

On the first day of creation light came into existence. “And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness.” Stained-glass art translates the beauty of light for us, and through this very Christian art form, we glorify God.

History of Stained-Glass Art

The Abbot Suger, the father of Gothic architecture, filled his abbey church of St. Denis, near Paris, with “the most radiant windows” to “illumine men’s minds so that they may travel through it (light) to an apprehension of God’s light.”

The history of stained-glass art begins with the history of glass with the Egyptians and Mesopotamians, the oldest known molded glass ever found. Next the blowing iron was invented in Babylon, but it was the Romans who adopted it and mastered the skill of working with glass. They learned that glass to which certain metallic oxides have been added will absorb wavelengths of certain colors and appear tinted. Both the Romans and the Egyptians showed great skill in the way they used metallic oxides as colorizers. Very small differences in oxide content can drastically affect the final color of the glass. Copper was used to make green and ruby-red glass; iron produced black, brown, and green; antimony, yellow; manganese was employed to make purple and amethyst glass. An opaque white glass was made by using tin.

Romans attempted to make flat glass by pouring slabs about one-half inch thick, but these attempts failed. The glass lacked transparency and only small panes of glass could be made using this method. The Romans did not overcome this limitation.

In fact glassmaking skills in Europe declined after A.D. 200. For about a thousand years, standards remained far below those of the Romans. The range of articles, as well as the quality of the material, was poor. The glass was of inferior color and marred by streaks and bubbles.

The revival of glass making skills in Europe emerged in Venice through trade contact with the Eastern Roman Empire (Byzantium). The Venetians imported these skills from the east and eventually redeveloped all the expertise of the Romans. Venetian glass products and their glass-making secrets were so much sought after that regulations were passed forbidding the emigration of workers. It wasn’t until the 16th century that most of the secrets and all of the manual skills of Venetian glass artisans had leaked out. Glass of improving quality was being produced all over Europe.

The art of cloisonné enamel, in which colors were separated by thin metal strips, is believed to have inspired stained glass in Byzantium. The oldest complete stained glass windows in the world, however, are in the Augsburg Cathedral in Germany and were glazed in the 11th century. Using smaller pieces of glass connected to one another by strips of lead, these large windows depicting the prophets were made. It was in the 12th century that large stained-glass windows began to appear in the new Gothic churches all over Europe.


The technique of making stained-glass windows was first described between 1110 and 1140 by the monk Theophilus. He categorized the process starting with the first step in which a full-size line drawing of the window was painted directly onto the top of a whitewashed table, showing the division of the various color areas into individual pieces of glass. Next, sheets of glass of the selected colors were chosen, and pieces were cracked away with a red hot iron which was applied to an edge of the sheet of glass, and a crack in the glass was started. This crack could then be guided more or less in the direction in which the iron was moved, resulting in a piece of glass of the right shape. The glass pieces were measured, allowing for a strip of lead between the pieces to hold them together. The details of the design were then painted onto the glass wherever necessary with vitreous enamel, and these pieces were fired in a kiln so that the enamel was fused to the glass. Now the windows were ready to be assembled.

In cross section, the grooved lead strips looked like the letter H. A piece of glass could be inserted in the grooves on either side of the lead strip. The first piece of glass was set in a corner between two corner leads. The next piece of glass was then placed next to this and a lead cut that went between them. This process was repeated until the entire window was assembled. All the leads were then soldered. The panel was then waterproofed by rubbing a putty compound that bound the glass in the groove in the lead. Now the panel was ready for installation.

Cathedral Age

The Cathedral Age sprang from new affluence where money showered the Church from kings and nobility as well as merchants. The cathedral became the symbol of wealthy, thriving towns. They became the centers for religious and artistic activity. They were centers of learning with schools attached to them, and from these the first universities evolved in the 12th century.

The Cathedral Age was the inaugural age for stained glass. Soaring vertical planes were made possible by the invention of the pointed Gothic arch. With the engineering innovation of flying buttresses which supported the vaulted height, thinner walls and larger window were possible. More light could enter the cathedral interior.

The art of stained glass reached its full splendor in the 13th and 14th centuries. Many of the colors were produced by the method of fusing stains to the surface of the glass. In this way images and designs were painted using glass as a canvas, vitreous enamel as their paint, but light as their real medium. No other art form uses light so directly. The viewer has an unearthly experience, a sense of seeing living forms. This experience was magnified by the great contrast of the dark interior of the 12th- and 13th-century churches with the deep dark colors of the stained glass. During the 14th and 15th centuries when architectural innovations allowed churches to open up to more light, brighter stained-glass colors were used. The dark rubies and blues of the earlier time could not be perceived in the lighter interiors.

In the Middle Ages the subject matter of stained-glass art was taken from the Scriptures, and the images not only told stories, but glorified God, the saints, and the Church. The cruciform formation of churches also resulted in four focal points in four different directions with exposure to sunlight in different ways depending on the time of day. The eastern exposure was often devoted to the resurrection. In Chartres, the west was devoted to the Last Judgment. The subject was not only determined by the clerics who supplied the master glazier with a program, but also by the donors who financed the project.


The process of making stained glass remains remarkably the same today as it was when first described by Abbot Suger 900 years ago. The main difference, says stained-glass expert John Krol, owner and founder of Jacksonville Art Glass, is that there is greater accuracy and uniformity in process with new technologies such as the electric kiln and chemical analysis using spectrophotometers. Today, a carbide wheel cutter is used to produce a fracture in a sheet of glass along a pre-determined line. Once the sheet has been lightly scored, a controlled break is achieved by “snapping” the glass, much like a twig, tapping the underside of the score line, or “nibbling” out small pieces in more difficult cuts.

Five hundred years ago studios were self-contained entities. “Studios used to make their own lead channels by melting the lead and pouring this molten material into forms—but this caused variations. Now variations are minimized and consistency is maximized,” Krol says. Glass also used to be made in the studios with each sheet having a unique variation in colors. Today stained glass is made in about seven companies in the U.S. and about four companies in Europe, mostly by machine, but some using the original mouth-blown techniques.

Advances in colors and enamel painting on the glass took place over the centuries, but the basic formula for painting stained-glass images and designs remained the same to this day. “The chemical composition of colors is more accurate,” says Sean Merchant, stained-glass painter at Jacksonville Art Glass. “Vitreous paints are composed of chemical substances that actually have glass in them. When this is painted on glass and fired, it fuses to the glass in a permanent bond,” Merchant says.

Merchant studied under the acknowledged master craftsman and glass artist David Millard of New Hampshire, who only recently died, but not before teaching his craft to young artists. Merchant uses only ox and boar hair brushes when painting because, he says, the quality of the filament is unmatched by synthetic materials.

In modern times artists have continued to explore the unique qualities of stained glass— the special refractory properties of opal-flashed antique glass, the graphic potentialities of the lead line, the bold effects of texture and relief that had become possible with slab glass and concrete—and to create a whole gamut of strange, brooding color harmonies the like of which had not been seen in stained glass since the 12th century.

Louis Comfort Tiffany of the early 20th century used stained glass in both religious and secular ways, depicting bunches of wisteria or vines laden with fruit as in the Heckscher House window. Actual folded glass adds to the illusion of robes in Tiffany’s depictions of the angels and saints at the First Presbyterian Church in Springfield, Illinois. Instead of painting robes and wings, Tiffany used the hand-formed glass that cooled in folds and then softened the look by layering the glass several pieces thick. The glass was made in his studio.

Glass art has also been revolutionized with digital imagery. At the Jerseyville United Methodist Church, in Jerseyville, Illinois, parishioners are welcomed into the interior by a luminescent image of a dove with wings outstretched against a background of the sunrise that spans the width of the sanctuary. “This is a completely new process that is remarkable in the amount of detail and brilliant color seen in these digital images,” says John Krol, whose studio, Jacksonville Art Glass, designed and created the piece.

No Longer Didactic

Although the difference in the technologies of traditional stained-glass imagery and digital imagery is clear, the greatest change may be in the subject matter of modern stained glass. In the 20th century, the stained glass used in churches is no longer didactic, i.e. teaching about Scripture and Christianity, but is used as a means to create an atmosphere. The depiction of the white dove to create an emotional response is a perfect example.

As society changes with the changing attitudes of the world, art changes, says Krol. “The chang­ing of tradition allows a freedom of art; less confined and more open to human experience. It’s why the more modern windows reflect less of historic value as far as figures and symbols, and more of an expression of an idea,” Krol says.

“The traditional Catholic Church is set by parameters set by the divine creator,” says Krol. “Art therefore becomes less human expression as it is a search for divine expression. This keeps it tightly bound by the traditions of the Church, which itself is disciplined by its founder and its apostolic succession.”

For this reason Krol values restoring the older, historical windows. “In restoring an old window it’s within an older structure and older congregation and deeper history. Most churches choose to preserve their history,” Krol says. “A new window affects a new architecture which defines a new attitude in the congregation. This new attitude is more influenced by the changing world,” Krol states.

And the world is changing. Stained glass is an art form that, because of its radiance, will continue to uplift our spirits whether the subject matter is traditional or modern. This art is a legacy that we have inherited from the Catholic Church. So many of our traditions have been undervalued and neglected. Studios like Jacksonville Art Glass have a vital function in restoring the old for future generations to understand the importance of our history. Those who work at restoring our Church and valuing our legacy are truly doing God’s work.