Listen to part of a lecture in an art history class.

OK, now uh, a sort of paradigmatic art form of the Middle Ages was stained glass art. Stained glass of course is simply glass that has been colored and cut into pieces and re-assembled to form a picture or a decorative design. To truly experience the beauty of this decorative glass you should see it with light passing through it, especially sunlight, which is why stained glass is usually used for windows. But of course it has other uses, especially nowadays. Uh, anyway, the art of making stained glass windows developed in Europe, uh, during the Middle Ages and was closely related to church building. In the early 1100s a church building method was developed that reduced the stress on the walls so more space could be used for window openings allowing for large and quite elaborate window designs. Back then, the artists made their own glass, but first they came up with the design. Paper was scarce and expensive, so typically they drew the design onto a white tabletop. They'd draw the principal outline but also outline the shape of each piece of glass to be used and indicate its color. Now in the window itself the pieces of glass would be held together by strips of lead. So in the drawing the artists would also indicate the location of the lead strips. Then you could put a big piece of glass on the tabletop and see the design right through it and use it to guide the cutting of the glass into smaller pieces. 

And the lead that was just to hold the pieces of glass together?

Well, lead is strong and flexible so it's ideal for joining pieces of glasses cut in different shapes and sizes. But up to the 15th century the lead strips also helped create the design.They were worked into the window as part of the composition. They were used to outline figures to show boundaries just like you might use solid lines in a pencil drawing. 

How did they get the color? I mean how did they color the glass?

Well, up until the 16th century stained glass was colored during the glass making process itself. You got specific colors by adding metallic compounds to the other glass making ingredients.So if you wanted red you added copper if you wanted green you added iron. You just added these compounds to the other ingredients that the glass was made of.

So each piece of glass is just one color?

Yes, at least up until the 16th century. Then they started... um... you started to get painted glass. Painted glass windows are still referred to as stained glass, but the colors were actually painted directly onto clear glass after the glass was made. So um with this kind of stained glass you could paint a piece of glass with more than one color. 

And with painted glass they still used the lead strips?

Yes, with really large windows it took more than one piece of glass, so you still needed lead strips to hold the pieces together. But the painters actually tried to hide them. So it was different from before when the lead strips were part of the design. And it is different, because with painted glass the idea of light corning through to create the magical effect wasn't the focus any more. The paintwork was. And painted glass windows became very popular. In the 19th century, people started using them in private houses and public buildings. Unfortunately, many of the original stained glass windows were thought to be old fashioned and they were actually destroyed, replaced by painted glass.

They actually broke them? That showed good judgment, real foresight, didn't it? 

Yes, if only they had known. Uh, and it's not just that old stained glass is really valuable today, we lost possibly great artwork. But luckily there was a revival of the early techniques in the mid-1800s and artists went back to creating colored glass and using the lead strips in their designs. The effects are much more beautiful. In the 19th century Louis Tiffany came up with methods to create beautiful effects without having to paint the glass. He layered pieces of glass and used thin copper strips instead of lead, which let him make these really intricate flowery designs for stained glass, which are used in lamp shades. You've heard of Tiffany lamp shades right? These of course took advantage of the new innovation of electric lighting. Electric light bulbs don't give quite the same effect as sunlight streaming through stained glass but it's close. So layered glass, Tiffany glass, became very popular and still is today. So let's look at some examples of different types of stained glass from each era.