Typical restoration and repairs of leaded glass panels
The first step in assessing a restoration project is often a visit to the site. Notes, measurements and photographs are taken to help determine the best course for a restoration program. While every project presents a unique set of conditions, the following examples represent some of the most common problems we encounter with windows in need of repair.
Cracked Or Missing Glass Pieces: Tight straight-line cracks can be repaired with edge-gluing or lead overlay if it is not aesthetically disruptive. A more complete repair involves replacing the broken piece with new glass of matching color and texture. These repairs can often be done on location without removing the panel from its frame.
Broken Pieces And Damaged Lead Caming: A panel with multiple breaks and missing or damaged lead cames needs to be removed from its frame to be repaired. Sometimes only sections of the broken panel need to be rebuilt with new lead and glass. Even extensive damage can usually be repaired, however, very severe damage may require re-leading the panel.
Bulging Or Deflection Of Panel: Over time, some leaded glass panels can bulge or distort. This frequently happens if the panel is not adequately reinforced or if the window’s design is intrinsically vulnerable to folding or hinging. Diamond-light panels are especially prone to this type of damage. Bulged panels should be repaired promptly as they can result in further damage such as broken solder joints, cracked glass, and water leakage. We can bring distorted panels back into plane before further repairs are made.
Broken Solder Joints/Missing Cement: Cracked solder joints are caused by stress on the panel such as bulging or repeated jarring. This problem commonly occurs within door or ventilator frames. Another problem, which is visible in this photograph, is missing cement. Leaded glass panels are cemented during fabrication using an oil-based putty compound. This compound fills the gaps between the glass and lead, thereby waterproofing the panel. This compound can dry out and wash away over time, leaving the window prone to leakage. Ideally the panels are removed and re-cemented. In certain circumstances, however, new cement can be applied on location.
Detached Reinforcement Bar: Large panels cannot support themselves on their own and therefore rely on round or flat steel bars for additional strength. These bars are soldered directly to the leads in the panel or secured with copper wire. Loose or detached bars result in a loss of support and may cause bulging or even separation of the panel from the frame. Removal of the panel is required to re-solder the bars or copper ties to the panel.
Frame Damage: Infrequent maintenance of paints and sealants can lead to damage of wood or metal framing. We can usually repair damaged wood with the application of epoxy resins and fillers designed for this purpose. Badly deteriorated sections of frame may need to be replaced before the wood is painted and sealed.
Panel Separation From Frame: Large leaded glass windows are often built in sections. These individual panel sections can sometimes separate from the frame if there is missing glazing compound or damage to the frame. The panel in this photograph pulled away because of a rotted wood sill. This panel was removed and a new sill was made and installed before re-setting the window.
Damaged/Failed Glass Paint: Glass paint is kiln-fired to permanently fuse it to the surface of the glass. If older pieces were not fired at a high enough temperature, this paint can degrade and fade or flake away. Care must be taken to restore these pieces, as the images can be fragile. We try to conserve all historic glass using a variety of techniques. However, if a painted piece is shattered or missing, we can expertly duplicate the piece and replace it into the panel.
Failed/Missing Sealant: Sealants and glazing compounds will eventually dry out and need to be re-applied. Even small cracks in these compounds can allow water to get through and cause damage.
Yellowed Protection Glass: Some clients may wish to use an exterior layer of glass or plastic to protect their windows from vandalism. If plastic protection glass is desired, we can install a polycarbonate (Lexan XL). This material is coated with a UV-filtering layer that is more resistant to yellowing over time.
Re-Leading Required: Under average conditions, the lead in stained glass panels lasts about 85 to 100+ years before the slow oxidation process begins to compromise its strength. Softer lead can then stretch or crack and initiate further structural problems. At this point, the most sensible course of action may be to take apart the window and re-assemble it with new lead, solder, and cement. The panel in this photograph is being taken apart in a water tank. It will then be re-leaded to an exact pattern made from the original.