The conservator’s eye: a stained glass Adoration of the Magi

Circle of Peter Hemmel von Andlau (Strassburger Werkstattgemeinschaft), Adoration of the Magi, 1507 or earlier (Munich), pot metal and colorless glass, vitreous paint, and silver stain, 72.4 x 45.7 x 1 cm (The Cloisters, The Metropolitan Museum of Art)


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[0:00] [music]

Dr. Steven Zucker: [0:06] We’re in the Cloisters, part of the Metropolitan Museum of Art in New York, looking at this gorgeous stained-glass panel. Usually, when people think about stained glass, they think about medieval churches, but this was actually produced during the Renaissance, and I’m really fortunate to be in the museum with Sarah Barack, a conservator who specializes in glass.

Sarah Barack: [0:25] When we look at a window, we kind of take for granted its beautiful, rich tones, its detailed painting. Not only was there a lot of thought and process involved, but a lot of skills and workmanship.

Dr. Zucker: [0:35] In the early 16th century, this would have been considered a very precious object, not so much because the materials themselves are costly, it’s not made out of real gold, but it did require a lot of expertise and a lot of fuel to heat the kiln in which it would have been made.

Sarah: [0:50] It’s not valuable gold, quite the opposite. It’s held together by a very base metal, lead. The lead creates the came, the bars that hold each piece of glass together.

Dr. Zucker: [0:59] What’s being depicted is, in fact, gold. This is the Adoration of the Magi, the three kings that here are honoring the newborn Christ Child with gold, with frankincense, and myrrh.

Sarah: [1:10] Not only did they bring their precious gifts, [they] also adorned themselves in beautiful costuming, from their velvety brocade robe to the incredibly ornate and detailed armor. When we think of stained glass, generally, the color of the glass isn’t really a stain.

Dr. Zucker: [1:25] This is called pot glass, and that would be glass that is entirely one color. That would be the kind of color that you would find, for instance, in a church like Chartres.

Sarah: [1:34] If there was a tragedy and you broke a piece of glass apart, for instance the Virgin’s blue robe that you see here, that color blue would go all the way through. It’s not an application on the surface. That’s different from the details we see.

Dr. Zucker: [1:44] This brilliant yellow is actually made out of silver.

Sarah: [1:47] It’s called silver stain. The application of silver salts to the surface of a glass, heated to a high temperature, which allowed the silver to actually migrate into the glass. We hear about nanotechnology today. Well, this is an early example of nanotechnology. Little tiny nanoparticles of silver creating a yellow hue of varying intensities.

Dr. Zucker: [2:07] In addition to the pot glass, which we see as red or green or blue, and in addition to the silver stain, which we see as this brilliant yellow, there’s also much finer work.

Sarah: [2:18] There are details in the robe, the hair of the Virgin, the face, the landscape. That’s all created by paint, but it’s not paint like you see in a painting on canvas. It’s actually paint that needed heat to allow it to set or fuse to the surface of the glass.

Dr. Zucker: [2:33] I think now in the 21st century, we take for granted flat glass, but this wasn’t poured into a flat mold. This actually was hand blown.

Sarah: [2:41] It’s probably done with cylinder glass.

Dr. Zucker: [2:43] They would heat up some glass. They would catch it as a ball at the end of a hollow tube, and they would blow into it, very much like we do with a soap bubble.

Sarah: [2:51] Then you would use gravity to allow that globe shape to turn into more like cylinder. That would be eventually transferred to another rod or punty, and allowed to be slit open and create a flat sheet. So imagine a piece of paper folded around to create a cylinder, and then you open it up and let it settle down into a flat sheet. It’s a good point that it wasn’t a painter, they probably bought their glass from merchants.

Dr. Zucker: [3:16] But clearly the artist would have had to understand the impact of different chemicals. So let’s look at one section of this panel and really try to understand how it was produced. I’m especially taken by the hat on the ground, just below the kneeling king and the Christ Child.

Sarah: [3:31] What you see are both the red of the glass itself, the yellow caused by the silver stain we talked about, and that colorless section is showing up as white right now, but it’s really just an area where the red has been removed. So in one piece of glass alone, you’ve achieved multiple details.

Dr. Zucker: [3:46] They are within the same piece of glass.

Sarah: [3:48] The artisan has avoided creating a thick black line, the lead in between, and the way this was done was really a virtuoso technique, removing red from a colorless glass.

Dr. Zucker: [4:02] So this is called flash glass. What’s happened is the glassblower is taking perfectly clear glass and blowing it into, say, a globe, and then that globe is dipped into another pot of molten glass, which in this case would have been red. So there would have been a thin layer of red glass on top of the original globe of clear glass.

Sarah: [4:21] It would allow him a lot of flexibility in terms of creating many colors.

Dr. Zucker: [4:25] Because what the artist was then able to do was just scrape away, either with acid or with some sort of abrasion, that outer layer of red where he wanted to expose the clear glass, for instance in that fur of the underlining, and the yellow also would have been cut back to the clear glass, and then those silver salts would have been added.

[4:44] When it was fired, that silver would have migrated into the surface of the glass. There’s also this lovely grisaille or gray, which is helping to define the details.

Sarah: [4:52] That’s that fire paint we talked about, and within the details, there’s both dark areas of wash and also beautiful bright highlights where the paint itself has been removed or stippled to allow the light to come through.

Dr. Zucker: [5:04] So the technical facility that was required to produce this hat is astonishing, and it would have begun with the glassblower himself, but then handed off to the artist who was responsible for the depiction.

Sarah: [5:14] It speaks to the talents and the skills of the collaborative workshop who created the panel, likely associated [with] Peter Hemmel, who was a well-known glass painter.

Dr. Zucker: [5:25] It’s remarkable to me how vivid the colors are, how little they’ve changed. This looks, I’m imagining, very much like it did in the early 16th century.

Sarah: [5:33] That’s what’s really special about glass in particular. Those colors remain true and vibrant. They don’t shift or fade the way you might see in a painting. This is very, very good condition.

Dr. Zucker: [5:45] Of course, glass is fragile. The glass itself can break. There can be losses.

Sarah: [5:50] We can see repairs in this panel, also. If we follow our gaze down from the top of the Virgin’s head to her lovely lock of flowing blonde waves, we might see a little line. That’s where the glass was broken and glued back together.

Dr. Zucker: [6:03] Just to the left of the Virgin Mary, in the frame of the panel, I can see that there’s a little break that forms an X.

Sarah: [6:08] That’s another area where the glass has broken and been repaired. In that same section of the framing element, we see a wedge shape, which includes a section of paint that looks warmer or browner in color. That looks to me like a repair as well.

Dr. Zucker: [6:22] There’s an interesting issue there. The conservator who was responsible for this repair wants us to be aware that this is not original, but also not distract us from enjoying the overall composition.

Sarah: [6:33] Those are really big questions that conservators actually grapple with when you are inpainting, or painting an area where something original is lost — how much to make it recede in space, how much to make it look a lot like the surrounding paint, and how much to subtly inform the viewer that something has been added or restored here?

Dr. Zucker: [6:50] All of this is a reminder that the closer we look at a work of art, the more there is to see, the more there is to understand, and the more there is to enjoy.

[6:58] [music]

Cite this page as: Sarah Barack and Dr. Steven Zucker, "The conservator’s eye: a stained glass Adoration of the Magi," in Smarthistory, October 10, 2017, accessed May 18, 2024,