Restoring Stained Glass Windows Keeps Company Busy

By Sam Lucero - Catholic Herald Staff
Published in a special section on Building and Renovation of "The Catholic Herald" the Milwaukee Diocese newspaper

MILWAUKEE – Like so many other elements of design in a church, stained glass windows service not only a function.  They are tolls of evangelization which transform Scripture into visual, colorful icons. 

While the origins of using stained glass date back almost to the development of glass making in the second century B.C., it wasn’t until the 10th century that stained glass windows became a form of religious expression inside cathedrals across Europe. 

Today, historic Catholic churches across Wisconsin, with their bell towers and spires serving as landmarks along rural and urban horizons, seek to preserve the stained glass windows that often date back over 100 years. 

From their 24,000 square foot studios in New Berlin, home of Conrad Schmitt Studios, three generations of Gruenkes are overseeing the restoration and preservation of church stained glass windows.

Although window conservation is only one facet of the internationally known company’s artistic endeavors, it is one in which the Gruenke family has helped pioneer. 

Since 1990, Conrad Schmitt Studios has restored or repaired stained glass windows in 55 churches in Wisconsin, including Milwaukee’s Cathedral of St. John the Evangelist and the Basilica of St. Josaphat.  Currently the company is restoring stained glass windows for the Cathedral of Christ the King in Superior, Wisc., and Sacred Heart Cathedral in Rochester, N.Y.

With a team of about 80 employees, consisting of project managers, craftsmen, artists, decorators and office staff, the studio is a beehive of activity, with six to eight projects under way at one time.

Under the watchful eyes and skilled craftsmanship of Bernard O. Gruenke, his son Bernard E., and grandchildren Gunar Gruenke and Heidi Emery, the company continues the tradition of liturgical art creation and restoration begun by Conrad Schmitt in 1889.

Bernard Sr., who purchased the company from the estate of Rupert Schmitt, Conrad’s son, in 1951, serves as president emeritus.  At 91, he remains an active part of the team, Bernard Jr., now in his fifth decade with the company, and his son Gunar and daughter Heidi follow in the elder Gruenke’s footsteps. 

According to Bernard Jr., stained glass conservation “is really not an art form, it’s more of a science.”  He said many stained glass studios do not follow the latest methods of conservation. Bernard Jr. recalls a newspaper article about one company restoring stained glass windows. 

You take one look at it and when you’re accustomed to conservation, you see four of five things wrong with a panel,” he said, “It’s very important to follow the latest proven methods of conservation.”

Conrad Schmitt Studios offers guidelines for churches to follow when considering the condition of stained glass windows.  The guidelines are posted on the company’s Web site,  Among the signs of windows in disrepair are glass breakage, sagging or bowing glass panels, deteriorated lead, and faded or peeling paint.

While deterioration of stained glass windows begins slowly, the damage tends to continue rapidly. 

I think it’s important that when parishes are looking at studios for their glass restoration, they compare apples to apples,” said Emery, “because a lot of these different procedures are a lot less expensive to execute and if you are not taking the time to vent the panels, to cut the glass the right way… you can do it for a lot less money but you’re not getting the longevity and the quality.” 

Churches considering stained glass work can have a window audit, in which Conrad Schmitt Studios evaluates the condition of windows.  Once a project begins, a more extensive evaluation and documentation process takes place.  According to Emery, churches possessing stained glass windows should consider documenting their collection, either through photographs or videotape. 

There’s been a number of projects we’ve done where there have been fires and we’ve actually replicated windows from little three-by-five photographs,” she said.

A lot of churches are getting to the point where they are actually paying to have us come in and document their stained glass – their condition and replacement costs – for insurance purposes,” added Gunar.

That’s important,” said Bernard Jr., “because they don’t realize how quick that investment in glass grows.  There are a number of churches in the city that are (valued) well over $2 million, just in their glass.” 

Major conservation projects, like the Cathedral of Christ the King in Superior – in which the entire collection of stained glass windows are being removed, transported to New Berlin for repair and restoration, and reinstalled – can take six to eight months to complete.  However, some churches, for economic reasons, prefer to draw out their stained glass projects over time.

The first step in a window conservation project involves creating “rubbings” or blueprints of window panels using acid-free vellum.  This serves as a permanent record and guide to the conservation work.  Copies of the rubbings can be duplicated for the church and local historical society.

Window panels are then dismantled and the worn lead roads are replaced with new leading.

Conservation entails saving as much of the original glass as possible.  Cracked glass is either repaired with conservation epoxy or replaced with new glass.

When you conserve a stained glass window, you must be subservient to the original artist and design,” said Bernard Jr.  “If we can build an environment in the interior of a church that last for decades or even centuries, that’s the most important thing.

When stained glass windows are refurbished, the re-installation process requires that steps be taken to avoid environmental wear such as rain, sunlight and temperature fluctuations.  Conrad Schmitt Studios uses protective windows frames and safety laminate glass.  To avoid the buildup of heat and moisture between glass layers, proper venting, using special metal tubes designed by Conrad Schmitt, is used to allow air to flow through while keeping moisture out. 

According to the Gruenkes, stained glass conservation projects completed by their studios have a life expectancy of 100 years or more.

Having spent their lives creating and restoring stained glass windows as well as church interiors, the Gruenkes see these holy edifices in a different light than other worshipers, admits Bernard Jr.

Sometimes it’s hard to pray, because you walk in and you see something that catches your eye and it’s so beautiful, or you think “this church needs a complete cleaning and the windows need restoring.”

What we’re trying to do through restoration or in designing new works for new churches, is to create a beautiful environment that has meaning and will last for decades, if not centuries,” he added.  “The old churches in Europe haven’t changed too much.  They’re still beautiful and I think we can have the same thing here in our country.” 

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