Earlier this week we looked at a commonly misused term in architectural parlance: “Victorian.” I’d posit that “stained glass” is one that gets tossed around incorrectly just as often. It is extremely unlikely that you have true stained glass in your home (unfortunately!). Truth is, in the U.S., actual, honest-to-goodness stained glass is a rare bird, especially in an area like Chicago, which was largely developed in the mid-to-late nineteenth century.
In general, there are two types of architectural glass windows: stained and art. Let’s run them down. (And please note that since the intricacies of glass manufacture are practically infinite and unknowable, we’re speaking in the broadest terms here):
STAINED GLASS: Pay attention, because here comes some science. By definition, stained glass is glass that has been colored via the addition of metallic oxide powders during its manufacture while it is still in a molten state. Different metallic compounds result in different glass colors: copper oxide makes green glass, gold makes red or purple, silver makes yellow, and cobalt makes blue (go figure). The most important takeaway: the color in stained glass is the result of a chemical reaction during the manufacturing process, not a surface application of color. Not all decorative colored glass is stained glass, it’s just become part of the vernacular to refer to it as such.
This technique for coloring and manufacturing glass using chemical additives has been around for thousands of years, but really reached its height in the late medieval period. The importance of stained glass in the development of church architecture is a story for another time (and one you’ve probably heard already), but suffice it to say that generally speaking, most of the true stained glass you’re going to encounter in your lifetime will be in the world’s cathedrals.
So imagine your artisinal guild has been asked to throw together a window for the town cathedral. Once the design has been agreed upon, your first step is to sketch up a cartoon of all of the lights, or openings, within the window. Using your cartoons, you then draw in a quilt-like leading pattern according to the necessities of the design. Some medieval artisans would forget the cartoon thing and just draw the design out on a big, whitewashed table, which became a template for cutting the glass. The patchwork was necessary because it was technically impossible to manufacture glass in large sheets, so even a large field of one color had to be made up of many smaller pieces of glass. The glass would be colored as outlined above while still molten, blown, cut to size, and arranged. If you were putting together a particularly decorative or representational stained glass window (say, of a Biblical scene), this is when you’d paint faces, hair, foliage, etc. directly on the surface of each piece of glass. Sometimes these were fired again, depending on the type of surface paint.
Now it’s time to bring everything together. Most stained glass is also came glasswork, meaning it’s fused into one piece via cames, or thin strips of metal slipped and soldered between glass pieces. Cames were traditionally made of lead, which is where we get the blanket term “leaded glass” (but copper, zinc, and lots of alloys were also used). The windows were, as you’d imagine, incredibly fragile due to their material and unwieldy size, and iron rods were often threaded across the window and used to facilitate installation — installation that required a couple dozen workmen.
Stained glass fell out of favor for a while in Europe, especially as a result of this thing called the Protestant Reformation, wherein people began rejecting the excesses and idolatry of the Catholic church. Again, we’re speaking very generally, but for the most part stained glass remained uncommon in new construction in the English-speaking world until the 19th century. That’s when people like A.W.N. Pugin and William Morris reignited interest in medieval architecture and craftsmanship, aided by Queen Victoria’s push toward chivalric morals (but you knew that).
ART GLASS: So maybe Morris and his friends were experimenting with traditional, chemical methods for coloring glass, but as stained glass became more popular, the demand necessitated mass production. Some sly entrepreneurs realized, hey, wow, if we just paint this normal glass, it looks a lot like that fancy stuff, and thus art glass was born. Well, decorative objects made of art glass had been produced in places like Italy for a while prior, but we’re talking windows, right? Right.
Perhaps the sliest of those sly entrepreneurs were John LaFarge and Louis Comfort Tiffany, both of whom developed and patented methods for coloring glass cheaply (well, kind of cheaply), quickly, and efficiently. Their two methods, by the way, were essentially the same process. LaFarge called it “opalescent glass” (and patented in 1879), while Tiffany called it “Favrile” (1892), but the product coming out of both studios was remarkably similar: each panel of glass had multiple swirling colors, an iridescent sheen, and a deliberately textured surface.
The actual production process has famously been kept under wraps, even after all this time, and no one outside of those two studios knew the “recipe” for opalescent glass. Speculation has it that Tiffany boned up on his medieval glassmaking history and used those same metallic oxides, but he applied them to the surface of the semi-solid glass rather than integrating them into the actual mix. The consensus seems to be that the LaFarge/Tiffany process was molecular change through surface absorption, while the traditional medieval method was molecular change through direct fusion. What is known, though, is that the glass was produced in a variety of ways: it could be molded, rolled, hand-stamped, conventionally poured, or even twisted and compressed to create more intricate striations.
Of course, Tiffany went on to build a decorative arts empire out of New York and pretty much leave LaFarge in the dust. But here in Chicago, someone else was doing a little glassperimentation…
BONUS! FRANK LLOYD WRIGHT’S ART GLASS: While Tiffany and LaFarge were producing windows for high-end buildings, the trend manifested among the masses in smaller feature windows in Victorian homes. These windows were usually very simple in terms of representation; the designs were usually floral or somehow natural. Often, the more decorative panels were colored using the direct surface-painting method, and then they were surrounded by “cathedral glass.” Cathedral glass was incredibly popular in domestic window production (not in cathedrals, go figure). It could be tinted using cheap dye, and then it was rolled, texturized, and cut into standard shapes, all by machine.
Frank Lloyd Wright, ever the contrarian, didn’t like Tiffany’s lavish, lush, sparkly designs, and he wasn’t so into what the plebians were installing, either. He was interested in the idea of decorative glass, though, and decided to start designing windows and light screens for his houses. Wright used strong geometric shapes in colors inspired by nature that would best compliment his Prairie School schtick, so most of his glass features brown/yellow/green/clear squares, rectangles, and triangles. Also, it was way cheaper to cut mass quantities of glass in straight lines, and Mr. Wright was a thrifty guy.
He also innovated by mixing different styles and finishes of colored glass with clear glass. Whereas Tiffany and LaFarge confronted the viewer head-on with a veritable iridescent rainbow of dense color, Wright was more sparing with his high-end glass so as to up its visual impact (and also probably to save some ca$h). He was traditional in one sense: Wright stayed quite true to the medieval came glass method, though he tended to us zinc or copper cames instead of the conventional lead.
Karen Sweeney, Preservation Architect at the Frank Lloyd Wright Trust, provides a few numbers that drive home Wright’s innovation in the use color, caming and innovation. In Wright’s Robie House, designed and built between 1908-1910, there are 114 art glass window panels with color in them and 26 art glass panels without any color in them – or 78% of art glass windows/doors have color in them. This number includes all 36 art glass door panels. Numbers don’t lie.
What have we learned?
– Stained glass with a capital S is beautiful and rare and chances are, you probably don’t have it in your house (sorry!). It gets its color from a chemical change via the addition of metallic salts while it’s in a molten state.
– Stained glass in vernacular usage usually refers to art glass, which you very well might have in your house!
– Art glass can be made in a variety of ways, but its heavy hitters, Tiffany and LaFarge, figured out a way to make it opalescent and incredibly vibrant.
– Frank Lloyd Wright’s glass remains incredibly popular (just stroll through any museum gift shop practically anywhere in the country), but it was far simpler and far cheaper to produce than any of the high-end art glass that preceded it.
– We didn’t learn this, per se, but the Smith Museum of Stained Glass Windows at Navy Pier is an excellent resource for the glass enthusiast (and also a great place to go to see a wide variety of the stuff in real life).
Let’s let Mr. Wright play us out.