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What Is Stained Glass?

Stained glass is the art of creating images, patterns, and decorative designs using pieces of colored glass fitted together — traditionally joined with strips of lead (called “came”) and supported by a rigid frame. When light passes through these colored panels, it transforms into something that has captivated humans for nearly a thousand years: walls of color that shift with the sun, turning architecture into something closer to music.

The medieval cathedrals of Europe remain the most spectacular examples. Chartres Cathedral in France contains 176 stained glass windows covering over 26,000 square feet, most of them nearly 800 years old. The blue glass at Chartres — “Chartres blue” — has a particular luminosity that glassmakers have studied for centuries and still can’t perfectly replicate. Stand inside on a sunny afternoon, and you understand why medieval visitors described these buildings as visions of heaven.

How Glass Gets Its Color

Glass is fundamentally sand (silicon dioxide) melted at extremely high temperatures — around 3,100 degrees Fahrenheit. In its pure form, glass is clear. Color comes from metallic oxides added to the molten glass during manufacturing.

Cobalt produces blue — from pale sky blue to deep sapphire, depending on concentration. Gold chloride creates ruby red, the most expensive color historically because gold is, well, gold. A single sheet of gold ruby glass could cost more than all the other colors in a window combined. Iron oxide produces green in its ferrous state and yellow-amber in its ferric state. Manganese gives purple. Copper can produce turquoise or red depending on the oxidation conditions.

Flashed glass is a clever technique where a thin layer of colored glass is fused onto a thicker layer of clear or lighter glass. This allows artists to etch or abrade through the colored layer to reveal the lighter glass beneath — creating detailed designs within a single piece of glass. It’s especially useful for red glass, which would be too dark to see through if made solid.

Silver stain — discovered around 1300 — was revolutionary. Applying silver nitrate to clear glass and firing it produces a range of yellows and golds. This meant artists could paint details like golden hair, crowns, and halos directly onto the glass without cutting separate pieces, dramatically increasing the detail possible in a design.

The Traditional Process

Making a stained glass window is slow, precise, and physical work.

The cartoon comes first — a full-scale drawing of the design, with each piece of glass outlined and numbered. Medieval artists drew cartoons on whitewashed tables; modern artists use paper or digital design tools. The cartoon determines every cut, every lead line, and every color choice.

Glass selection involves choosing sheets of colored glass for each section. Handmade glass — mouth-blown or hand-rolled — has variations in thickness, color intensity, and texture that mass-produced glass doesn’t. These variations are a feature, not a flaw. They create the visual depth and life that makes handmade stained glass glow differently from machine-made windows.

Cutting shapes each piece of glass to match the cartoon pattern. A glass cutter (diamond-tipped or carbide wheel) scores the surface, and the glass is broken along the score line. Curved cuts require skill and practice — one wrong snap and the piece shatters.

Painting adds fine detail that leading alone can’t achieve. Glass paint — a mixture of iron oxide, ground glass, and a binding medium — is applied to the glass surface and fired in a kiln at around 1,200 degrees Fahrenheit, fusing permanently. Faces, hands, drapery folds, architectural details, and text are all painted.

Leading assembles the pieces. H-shaped lead strips (came) hold the glass pieces together, their channels gripping each edge. The intersections are soldered for structural integrity. Finally, putty (a mixture of linseed oil, chalk, and sometimes lamp black) is pressed under the lead flanges to waterproof the window and add rigidity.

The Cathedral Achievement

Gothic cathedrals were essentially experiments in how much stone wall you could replace with glass. The invention of the flying buttress — an external support arch — transferred the building’s weight to external structures, freeing interior walls to become vast expanses of stained glass.

The results were intentional. Cathedral builders weren’t just decorating. In a largely illiterate society, stained glass windows told Biblical stories, depicted saints’ lives, and illustrated moral lessons. They were “the poor man’s Bible” — visual instruction for people who couldn’t read. But they were also theological statements about the nature of divine light, the transformation of ordinary materials into something transcendent.

Sainte-Chapelle in Paris (completed 1248) is the ultimate expression of this idea — a chapel that’s essentially a glass box supported by thin stone columns, with 6,458 square feet of stained glass rising 50 feet. On a sunny day, the interior becomes a space of pure color that defies description in words. You have to stand in it.

Modern Stained Glass

The tradition didn’t end with the Middle Ages. The 19th century saw a major revival, with the Arts and Crafts movement and artists like Louis Comfort Tiffany bringing stained glass into secular contexts. Tiffany’s lamps and windows — with their nature motifs, opalescent glass, and copper foil technique (an alternative to lead came) — made stained glass a domestic art form.

The 20th and 21st centuries pushed further. Marc Chagall created magnificent windows for cathedrals, synagogues, and the United Nations building. Gerhard Richter designed a window for Cologne Cathedral using 11,500 squares of colored glass arranged by random computer algorithm — no figures, no narrative, just pure color. Contemporary artists like Judith Schaechter create stained glass panels that hang in galleries as fine art, depicting contemporary subjects with traditional techniques.

You can learn the basics yourself. Introductory stained glass classes teach cutting, copper foiling, and soldering — enough to make a simple suncatcher or small panel. A starter toolkit costs $100-200. The materials are accessible; the mastery takes a lifetime. But the first time you hold a piece you’ve made up to a window and see light transform through colored glass you cut and assembled yourself — you’ll understand why people have been doing this for a thousand years.

Frequently Asked Questions

How is stained glass made?

Traditional stained glass involves several steps: designing the pattern (cartoon), selecting colored glass sheets, cutting glass pieces to shape using a diamond or carbide cutter, wrapping each piece's edges in copper foil or fitting them into lead came (H-shaped lead strips), soldering the joints, applying putty for waterproofing, and installing the finished panel. The glass gets its color from metallic oxides added during manufacturing — cobalt for blue, gold for red, iron for green. A single cathedral window might take months or years to complete.

How old is stained glass?

The oldest surviving complete stained glass windows date to around 1100 CE — the Prophet Windows in Augsburg Cathedral, Germany. But colored glass itself is much older. Ancient Romans used colored glass in windows, and fragments from the 7th century have been found in English monasteries. The art reached its peak during the Gothic period (12th-15th centuries) in the great cathedrals of France, England, and Germany. Chartres Cathedral alone contains 176 stained glass windows, most dating to the 13th century.

Is stained glass only found in churches?

Not at all, though churches have the most famous examples. Stained glass appears in homes (Tiffany lamps and windows were hugely popular in the late 1800s), public buildings, museums, train stations, restaurants, and modern architectural installations. Louis Comfort Tiffany made stained glass a secular art form in America. Today, contemporary glass artists create installations for corporate buildings, private homes, and galleries that have nothing to do with religious imagery.

Further Reading

• The Stained Glass Association of America
• Victoria and Albert Museum - Stained Glass
• The Metropolitan Museum of Art - Stained Glass