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Christmas Cover story

Creating a stained glass window

After the nuns of Visitation Academy approved Lea Koesterer’s scale watercolor of “Visitation,” the first step in creating the window itself was selecting the glass.

Koesterer taped small samples of colored glass to a clear window in her studio to test how well the variety of hues work together. Background interference, white light from other windows and color saturation are some of the factors that can make deeper shades of color appear almost black.

Following this selection process, Koesterer ordered German hand-blown glass from an importer in San Francisco.

While the glass was on order, she spent two days at Visitation Academy in spring 2000, enlarging the line drawing, known to artists as a cartoon. Using school equipment, she projected the watercolor image onto a wall at the window’s actual size, 7 feet high by 14 feet wide, and traced it onto paper.

In a trip to the fabricator of the window’s sash, Koesterer made templates of the outer dimensions of the opening. With these and the cartoon in hand, she made the patterns for cutting each piece of glass and for assembly.

Cutting the pieces out of sheets of glass is another stage of the work calling for careful selection. Unlike machine-made glass, the handmade glass that Koesterer used has great variation of hue even within a single sheet. Where the glass is thicker, color saturation is greater.

Also at this stage, the figures’ hands and faces were painted on and fired at over 1,100 degrees Fahrenheit.

After the glass is cut, it is assembled with leading and soldered together. After one side was soldered, the entire window was turned over and soldered on the other side. Because a stained glass window is extremely fragile at this point, Koesterer used a board to raise the window to a vertical position and then lower it on the same board to expose the other side for soldering.

Next, the window was weatherproofed on both sides. Weatherproofing material, besides adding protection from the elements, adds structural support by filling in the air space between the glass and the lead.

In the final stages, a patina was added to the joints, making the lead and solder the same dark hue. Reinforcing rods were added, so when the window heats up in the sun and the lead gets softer, the rods keep the window from buckling.

Finally, in September 2000, the window was installed.

-- Teresa Malcolm

National Catholic Reporter, December 21, 2001