"I look at the texture, color, and amounts of white or amber in it," said Caldwell of one cracked pane. "And if you can't match it, glass matches can help."
As sometimes is the case with a foreign, antique piece of glass, a specialized matching service is hired for assistance in finding obscure colors or patterns.
After carefully matching the broken pane to a replacement, Caldwell's steady hand and tricks of the trade ensure the new piece will never be distinguishable from its brothers.
First a template is made on paper to pattern the new piece, which is later traced onto the new sheet of glass. After scoring the pattern lines in the brittle glass, Caldwell uses running pliers to break the glass along the scored edges. It is more artful breaking than precise cutting.
"We have to encourage the glass to break where we want it. Even if it breaks with a rough edge, as long as it fits under the lip of lead, it's OK," demonstrated Caldwell.
The orange-handled running pliers have a wide nose that curves at a slight 2-degree arc. It only takes 2 degrees of pressure against a score-line to snap the piece, Caldwell said above the glass's audible snap.
As the new piece is being formed, the lead came (a slender lead rod used to hold together panes of glass) and cement around the old pane are rubbed with a drying talc, to make the cement easier to separate from the broken glass.
"A lot of the old pieces of cement will fail, and the pieces will get loose. You have to dig out all the old cement and replace it," told Caldwell.
After the old cement is removed, the lead came is cemented to the new glass as it is fitted into place. The finished product is held up to the light for close inspection before being sent home, good as new.
This process has grown in demand as containers full of small stained-glass window hangings are being shipped from England's old row houses, said Caldwell, as Europe modernizes old neighborhoods.
"Everybody had artwork in their windows, it was just the culture," said Caldwell.
With wooden frames and simple lines, these colorful square and rectangle pieces are becoming popular additions to many homes across the nation, but as they are being shipped, they are suffering damages, said Caldwell.
Aside from rough shipping, Caldwell listed gravity as stained glass's worst enemy, followed closely by ammonia cleaning products, such as Windex.
"The ammonia will react with the leading and the cement, mainly the cement, and cause a white moldy powder to form," Caldwell explained.
The formations will not harm the glass, but the piece should be re-washed and dried carefully to remove the eyesore and better preserve the cement.
After a piece has been created or shipped and refurbished, the glass art can last for centuries with proper care. A sun-catching work of art can easily become a family heirloom to last beyond the next turn of the century.
"It is something built to withstand 100-plus years. So as long as you don't drop it, it should last," said Caldwell. "I think this is a great business to be in because it is an art form that transcends time, and is looking for a brighter future."