Pure luck. That is honestly the best way to describe why we can still talk about the stained glass windows of Notre Dame Cathedral Paris in the present tense. When the roof went up in flames back in April 2019, most of the world assumed the glass was toast. Lead melts at about 327°C. The fire was hitting temperatures over 800°C. You do the math. Yet, miraculously, the three iconic Rose Windows—the North, South, and West—stayed in their sockets. They didn't shatter. They didn't melt into colorful puddles on the stone floor.
It's kinda wild when you think about the physics of it. The heat was intense enough to warp steel, but the massive stone walls acted as a heat sink, and the draft created by the collapsing spire actually pulled some of the highest temperatures away from the glass. But "survived" is a relative term. While the glass didn't melt, it was essentially "choked" by a thick, toxic layer of lead dust and soot.
The Three Roses: More Than Just Pretty Patterns
If you've ever stood in the nave, you know the North Rose is the one that hits different. It's almost entirely original 13th-century glass. That’s nearly 800 years of survival. Most people don't realize that while the South Rose is famous, it’s actually been heavily restored over the centuries, especially during the 19th-century overhaul by Eugène Viollet-le-Duc.
The North Rose keeps its cool, literally. It uses deep blues and purples to depict Old Testament figures surrounding the Virgin Mary. It’s about 13 meters in diameter. Big. Really big. The light that filters through it on a cloudy Parisian morning has this specific, heavy quality that modern glass just can't replicate. Why? Because medieval glass wasn't "pure." It had impurities—seeds, bubbles, and varying thicknesses—that catch the light and bounce it around in ways that perfectly flat, modern industrial glass never will.
The South Rose, or the "Rose du Midi," was a gift from King St. Louis. It’s flashier. It deals with the New Testament, apostles, and martyrs. But because it’s on the sunny side of the cathedral, it has taken a beating from the elements for centuries. By the time Viollet-le-Duc got to it in the 1800s, it was a mess. He swapped out a lot of the panes, which is why the colors there feel a bit more "vibrant" and structured compared to the moody, ancient vibe of the North Rose.
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What Happened During the Restoration?
After the fire, the cleanup was a logistical nightmare. You couldn't just go in with a bucket of Windex. We’re talking about stained glass windows Notre Dame Cathedral Paris enthusiasts have studied for lifetimes, now covered in micro-particles of lead.
Starting in 2022, the windows were meticulously removed. Master glassmakers from across France—and even a few from Cologne, Germany—stepped in. The process was basically a high-stakes spa day for ancient artifacts. They used cotton swabs soaked in a mixture of water and ethanol. Gentle. Painfully slow.
The goal wasn't to make them look "new." That would be a tragedy. The goal was to remove the gray film of soot so the light could actually pass through the silver stain and the pot-metal glass again. In some of the smaller clerestory windows, they found layers of "grisailles"—that's the grayish paint used for shading—that had started to flake. Conservators had to consolidate these layers before they could even think about cleaning the surface.
The Controversy of the New Windows
Here is where things get spicy. While the historic Rose Windows are being preserved exactly as they were, President Emmanuel Macron and the church authorities decided to launch a competition for new stained glass for six of the chapels on the south side.
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The idea is to leave a "21st-century mark" on the cathedral. Not everyone is happy. Purists are basically losing their minds. They argue that Notre Dame is a unified masterpiece and dropping contemporary, abstract glass into a Gothic framework is like putting a spoiler on a vintage Ferrari.
But history tells a different story. Notre Dame has always been a patchwork. The 19th-century windows people love now were hated when they were first installed because they weren't "authentically medieval." It's a cycle. The new windows will likely be abstract, focusing on the "breath" of the Holy Spirit, or some other ethereal concept that allows for a lot of light, which is something the cathedral desperately needs now that the interior stone has been cleaned back to its original creamy white.
The Chemistry of the Color
Why do the blues look so blue? It's all about the cobalt. In the 12th and 13th centuries, glassblowers added metal oxides to the molten glass.
- Cobalt oxide gave them that deep, piercing "Chartres blue."
- Copper oxide resulted in rich reds or greens depending on the oxygen levels in the furnace.
- Gold chloride was sometimes used for those rare, shimmering cranberries and pinks.
The "silver stain" technique, which became popular later, allowed artists to paint onto the glass and then fire it again, turning parts of a clear pane yellow or orange. This was a game-changer for depicting golden hair or crowns without needing extra lead lines. When you look at the stained glass windows of Notre Dame Cathedral Paris today, you're seeing a literal timeline of chemical engineering.
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Visiting Notre Dame in 2026: What to Look For
The cathedral is officially back open, but the experience is different now. The stone is brighter, which means the contrast with the windows is even more dramatic.
When you go, don't just stare at the big Roses. Look at the smaller windows in the choir. You’ll see the difference between the 13th-century glass and the 19th-century replacements. The older glass is thicker, more "jewel-toned," and less transparent. The 19th-century stuff is more "pictorial," almost like a painting on glass.
Also, check the light on the floor. On a clear day, the South Rose throws "projections" of color onto the stone. It’s a literal light show that has been running for centuries.
How to actually appreciate the glass when you're there:
- Bring binoculars. Seriously. Most of the best detail—the tiny faces of the saints, the weird little demons in the corners—is 20 meters above your head. You can't see the brushwork with the naked eye.
- Time your visit. Mid-morning is best for the North Rose. Late afternoon is when the South Rose absolutely explodes with light. If you go at noon, the sun is too high and the colors can look washed out.
- Look for the "new" glass. Try to find the six chapels with the contemporary windows. Compare how the light feels coming through them versus the medieval glass. It’s a great way to understand how glass technology has changed from "filtering light" to "directing light."
- Notice the lead lines. These aren't just there to hold the glass up. They are part of the drawing. In the best windows, the lead follows the contours of the figures, adding depth and shadow.
The stained glass windows of Notre Dame Cathedral Paris are not just decorations. They are survivors of war, revolution, and one hell of a fire. They are a reminder that even the most fragile things can endure if we care enough to clean the soot off them. The fact that we can still stand in that nave and see the same blue light that a peasant in 1250 saw is, honestly, a bit of a miracle.