Church Stained Glass Q&A

Here are some of the most frequently asked questions by churches regarding stained glass windows.

Our stained glass windows are bulging, sagging and bowing. Why is this?
A stained glass window consists of many individual pieces of glass held together by strips of lead caming. The average life of the window is usually 70 to 100 years. As the lead and putty decay, the entire structure of the window begins to weaken under its own weight. Expansion and contraction of the lead due to heat from poorly ventilated exterior protective coverings also contribute to the window’s movement. The sagging and bowing are evidence of the final stages of this process.

If this problem is not addressed, the glass will crack or fall out of the caming until the window eventually collapses. However, proper restoration can extend the life of the stained glass window for up to another 100 years.

Our stained glass windows are between 70 and 100 years old. What signs of deterioration should we look for?
When you inspect your windows, be sure to use a bright light and look for the following signs of decay:

* Sagging or bulging
* Cracked or missing glass
* Rattling or loose sound when stained glass is tapped
* Unattached reinforcement bars and/or broken solder joints
* Light, water or air leaks through the stained glass window
* Previous repairs, such as mismatched glass, silicone glue, or excessive addition of reinforcement bars
* Minute cracks in the lead (best seen with a flashlight and a magnifying glass)
 
Any one or more of these problems would indicate the need for maintenance or restoration of your stained glass windows.

What can we do to extend the life of our stained glass windows?
The type of restoration of old stained glass windows depends on the level of deterioration. There are a few options for restoration.

At least every 20 years, windows should be assessed and have general maintenance performed. This may include cleaning, removal and weatherproofing with putty, and documentation of their condition.

In cases where the lead is still in good condition, but the stained glass is sagging or buckling, the windows may be removed, flattened, repaired, and puttied.

In cases where the lead has decayed, stained glass windows will not sustain this type of repair; a complete restoration including re-leading may be necessary. Re-leading and restoration is the most thorough and cost-effective option. It will return the window to its original strength and condition, extending the life for another 100 years.

Exterior glazing or covering of stained glass windows is also an option to prevent deterioration to a stained glass window. Exterior glazing includes installing a panel of clear glass over the exterior of the stained glass.
 
Is stained glass window restoration cost-effective?
Unlike major building repairs, such as roofing and plumbing, stained glass repair or restoration does not have to be done all at once. A maintenance program can be spread over a period of years. But, by putting off maintenance, stained glass windows continue to deteriorate, making repairs more costly overall.

If you consider that a restoration can extend the life of the stained glass window for another 100 years, the investment is more cost-effective than most major building repairs.

What is exterior glazing for stained glass windows?
The term “glazing” means to cover with glass. Exterior glazing for stained glass windows involves installing a layer of clear glass to the exterior of a stained glass window to protect the window from weather, impact, and other instances that may promote deterioration of the stained glass or lead caming.

Will installing an exterior glazing to protect our stained glass windows solve our problems with deterioration?
Exterior glazing can be beneficial if it is correctly installed with a specialized frame.

An extensive study of exterior glazing installations funded by the Department of the Interior and directed by Inspired Partnerships of Chicago inspected and evaluated 120 installations around the country and found that more than 90 percent were incorrectly installed. Improper installation of exterior glazing can actually accelerate the decay of stained glass windows.

The signs of improperly installed exterior glazing include:

* Clouding or yellowing of the window covering
* A space of less than one inch between the stained glass window and the exterior glass
* Lack of air movement in between the layers, causing excessive heat buildup in the stained glass window
* Polycarbonate or acrylic screwed directly onto the existing window casing. These types of frames often crack and become unsealed around the perimeter of the frame, allowing rain and snow infiltration – eventually causing original wood frames to rot.
 
What is the proper installation of exterior glazing?
Many exterior glass applications are installed with complete disregard for the original architectural intent. They are often installed in a "tic-tac-toe" pattern directly over the curved framework housing the stained glass.

A more visually appealing exterior glaze can be installed in a custom formed frame, which is fabricated to follow the original framework or tracery. This would include a perimeter frame rather than screwing and gluing the exterior glaze to the original wood frame. These frames also allow the space between the stained glass window and the exterior glazing to be ventilated, which allows natural airflow to cool the space between the two and prolong the life of the stained glass.

Our existing exterior coverings are cloudy and yellow. Can they be cleaned?
Unfortunately, no. In the 1970s, polycarbonates and acrylics seemed to be the best product for the protection of stained glass windows. Usually within 10 to 12 years, these products, especially Lexan, turn cloudy and yellow. These types of coverings are functional as far as protecting the windows from impact, but have a limited life and are not visually appealing.

Although this material is recommended if threats of vandalism or other extreme conditions exist, for protecting standard stained glass windows from hail, pebbles, and small projectiles, quarter-inch plate glass, or tempered glass, is sufficient. The expense of repairing a few pieces of plate glass in a rare case of breakage is minimal compared to the cost of replacing the polycarbonate glazing every 10 to 15 years.

We are building a new church and would eventually like stained glass windows. How do you plan for future stained glass installation?
The best time to start planning for stained glass windows is during the construction phase of a new church. Custom-built frames can be designed to house the clear insulated windows and have a channel already in place for stained glass to be installed at a later date. An optional "cap bead" can even conceal the stained glass channel until the new windows are installed. This saves time and money when the church is ready to design and install stained glass.

This type of frame also makes restoration and repair easier down the road. The frames are designed so either the exterior insulated glass or the stained glass can be removed without disturbing the other panel.

What is the process of designing new stained glass windows?
The general process for completing a successful stained glass project includes:

* Initial discussions regarding themes, plans, and desired results
* Determination of preferred style and artist
* Estimate  
* Review of company’s and artist’s expertise and abilities based on overall body of work
* Approve studio and artist, agree to terms, and sign contract
* More discussions with artist regarding themes and desires
* Artist renderings for approval or revision until client is satisfied
* Fabrication of windows 
* Final installation

This information is courtesy of Classic Glass, www.classicglassstudio.com.