Beginning sometime in the 9th century A.D., stained glass was used to educate a mostly-illiterate population with narrative or pictorial scenes that told stories from the Bible or about particular saints.  Other stained glass windows are very large and spectacular designs of color that were simply meant to inspire.

Glass was known to have existed in Egypt and Babylonia as long ago as 3000 B.C. The art of glass blowing may have originated in Syria, and it made its first appearance in Rome in the 1st century B.C.  From the 1st to the 4th centuries, glass is known to have been used in most Romano-British homes where it was used to seal the "wind-holes" (from which we get the word "window") from the weather and birds.

The earliest record of use of glass in a church is in the English church at York sometime in the late 600's A.D., and colored glass was used as early as the late 700's in St. Paul's church in Rome.

The earliest examples of stained glass windows consisted of pieces of colored glass that had been inserted into holes that had been cut in panels of wood, marble, alabaster or gypsum.

Stained glass panels were usually commissioned by a wealthy patron individual or by a church.  The artist would produce a preliminary sketch called a vidimus (which literally means "we have seen") for the patron to approve prior to beginning the final piece.  After approval, the artist was in complete control of the artistry of the final stained glass piece.

From the 12th to 15th centuries, the methods for creating a stained glass piece remained mostly unchanged. 

Creating the piece began with translating the vidimus onto a flat whitewashed surface with a full size "cartoon".

Bits of clear glass were then cut to a rough shape with a red-hot pointed iron, and trimmed to the final shape with a grozing iron.  The pieces were then laid onto the cartoon to be colored.

A dark opaque enamel paint, was then applied to the glass.  To achieve the various colors, pigments were mixed with a metallic oxide of iron or copper, powdered glass, and wine or urine.  The resulting paint was applied with brushes, and various shades and textures were produced by using different types of brushes or sharpened sticks.

The painted glass pieces were then stacked in pans with layers of ash or quicklime between them.  They were then placed into a kiln, where the heat fused the paint to the glass.

After cooling, the pieces of glass were laid back onto the cartoon, where H-shaped strips of lead were fitted tightly between them.  The lead strips were soldered together wherever they intersected.

The finished stained glass panels were then fitted into the window opening with the painted surface on the interior side.

In the 14th century, stained glass makers discovered that a derivative of sulfur of silver could stain glass yellow.  This was a real breakthrough, because after a piece of stained glass had been finished, they could apply the sulfur of silver to the opposite side of the glass, producing more than one color on a single piece of glass.  For example, wherever applied to a piece of blue stained glass, the color seen through the glass was a brilliant green.  This process reduced the number of individual pieces of glass used in the piece.

By the 16th century, the enamel paints were improved by mixing different types of metal oxides with flux (a soft powdered glass with a melting temperature that was lower than the glass piece).  For example, copper would produce green, cobalt would produce blue, and manganese would produce purple.  After applying the paint to the glass, it would be fired in a kiln, where the flux would melt, adhering the color to the glass piece.

Stained glasswork is an ancient, fascinating and beautiful art form that deserves to be preserved and used in our churches.  In the hands of a master, it can lead to pieces of stunning and inspiring beauty for those looking from the inside. But more importantly, it might affect the unchurched who, from the outside, might just be inspired to see the inner light.