Stained glass has had various levels of popularity throughout history. The 12th and 13th centuries in Europe have been designated as the Golden Age of Stained Glass. However , during the Renaissance period , stained glass was replaced with painted glass , and by the 18th century it was rarely , if ever , used or made according to medieval methods. During the second half of the 19th century , European artists rediscovered how to design and work glass according to medieval principles , and large quantities of stained glass windows were made.
A leaded stained glass window or other object is made of pieces of glass , held together by lead. The pieces of glass are about 1/8-inch (3.2 mm) thick and bound together by strips , called "cames" of grooved lead , soldered at the joints. The entire window is secured in the opening at regular intervals by metal saddle bars tied with wire and soldered to the leads and reinforced at greater intervals by tee-bars fitted into the masonry. A faceted glass panel differs slightly from traditional leaded stained glass in that it is made up of pieces of slab (dalle) glass approximately 8 inches square , or in large rectangular sizes , varying in thickness from 1-2 inches (2.5-5 cm). These slabs are not held together with lead; rather they are embedded in a matrix of concrete , epoxy , or plastic.
Glass is made by fusing together some form of silica such as sand , an alkali such as potash or soda , and lime or lead oxide. The color is produced by adding a metallic oxide to the raw materials.
Copper oxide , under different conditions , produces ruby , blue , or green colors in glass. Cobalt is usually used to produce most shades of blues. Green shades can also be obtained from the addition of chromium and iron oxide. Golden glass is sometimes colored with uranium , cadmium sulfide , or titanium , and there are fine selenium yellows as well as vermilions. Ruby colored glass is made by adding gold.
The Manufacturing Process
Stained glass is still made the same way it was back in the Middle Ages and comes in various forms. For the glass used in leaded glass windows , a lump of the molten glass is caught up at one end of a blow pipe , blown into a cylinder , cut , flattened and cooled. Artisans also vary this basic process in order to produce different effects. For example , "flashed glass" is made by dipping a ball of molten white glass into molten colored glass which , when blown and flattened , results in a less intense color because it will be white on one side and colored on the other.
So-called "Norman slabs" are made by blowing the molten glass into a mold in the shape of a four-sided bottle. The sides are cut apart and form slabs , thin at the edges and as much as 0.25 inch (0.6 cm) thik) at the center. Another form of glass , known as cathedral glass , is rolled into flat sheets. This results in a somewhat monotonous regularity of texture and thickness. Other similarly made glasses are referred to as marine antique , but have a more bubbly texture.