Owners of old houses appreciate the beauty of stained glass. In some cases, stained glass may have been the emotional “reason” that prompted you to purchase your home. But as with so many other aspects of old home ownership, stained glass windows need upkeep and care. Below are some suggestions on how to care for your windows and how to recognize when to call in an expert.
A stained glass panel is constructed from 1) individually cut pieces of clear or colored glass, or bezels; 2) joined by a matrix of lead or copper foil. Wine lead dates from medieval times and is the traditional method of mounting led glass panels. Zinc wine is associated with the prairie designs of Frank Lloyd Wright and his contemporaries. Copper rolling is the method introduced by Louis Comfort Tiffany, and is the preferred method for constructing intricately designed artistic glass panels and shades. An additional step in the construction of LED glass panels is the application of cement to fill the space between the glass and the interior surface of the lead or zinc panel. Cement is applied to the front and back of the panel to waterproof it and add strength to the panel. Large panels must also be reinforced with tie bars or rebar.
Inspect your windows for age and sagging. To assess the condition of lead or zinc cams, look for telltale signs of metal fatigue and corrosion. Old lead is still functional if the exposed metal face (the flanges) can be lifted and flattened without cracking. Lead covered in a fine white powder has oxidized and has reached the end of its useful life. The zinc covered with small white spots is also worn. Examine the metal for hairline cracks near the joints, particularly around the edge of the panel. These indicate metal fatigue.
Large or specially made glass panels are often reinforced with steel or brass bars. Approximately 1/8″ thick by ¼” wide, these saddle bars are attached to cams and notched into the frame to stiffen the window and help support the weight of the panel. Some reinforcing bars are welded to the cams, while others are attached with stranded copper wires. If the bars have separated from the cam, they must be reattached using the original method. Bars that have split the cam will require reattaching by a professional restorer.
If the panel has developed a bulge, measure its depth. A panel that is 1″ or less out of line and not vibrating should be professionally examined, but may not need repair. Panels that are more than 1½” out of line should be removed from the window and smoothed and be refitted professionally.
Check the glass. Due to the difficulty of smoothing out some old glass, it is preferable to repair cracked glass rather than replace it. And not all cracks need to be fixed. If the crack is small and there is no danger of it falling out, leave it alone. If glass is missing or badly cracked, call a professional. If the repairs are minimal and the panel is large, a field repair may be possible.
If you have to transport the glass to a professional refinisher, start by securing any loose cams and glass panes with masking tape. (Do not use duct tape!) Remove the sheet with the panel still attached. For added security, place the panel on a larger sheet of plywood and tape it down. Smaller panels can be wrapped and laid flat in a wooden crate.
Clean an undamaged leaded or copper-plated glass panel with a soft cloth and a pH-neutral soap. Wring out the cloth well. Avoid abrasive products that can scratch the glass or metal. Do not use spray products or products that contain ammonia. The liquid can get under the foil or lead, and the ammonia can react with the lead or cement. Bathroom or kitchen windows can be cleaned with a dampened #0000 steel wool pad to remove soap scum, grease and mildew. Polish with a paste product such as Glass Wax or a stained glass polish available at any stained glass supply retailer. Use a soft cloth to apply the paste, allow to dry, and polish. CAUTION: This process may release lead dust into the work area. Clean any surfaces surrounding the panel (frames, sills, and floor) with soap and water to remove any lead residue. And wear a dust mask.
Protective glazing, while not required, can provide protection for your stained glass window from vandalism or a stray baseball. To maintain aesthetics, the shutter frame should be similar in material to the original frame. Depending on local building codes, glazing may be double-strength or Plexiglas(R). Please note that plastic glass will yellow and scratch over time. Lexan(R), which does not yellow, scratches very easily. Double strength tempered glass is expensive, but offers the best protection.