IDENTIFY THE PROBLEMS
Our staff has more than eighty years combined experience repairing historic stained glass. We actively participate in worldwide stained glass conservation forums and work with the Michigan Stained Glass Census to document repairs and new construction so that it may be recorded and digitally archived in efforts to preserve this facet of Michigan's cultural heritage. While exploring new technology and tools in our custom fabrication, we strive to maintain traditional methods when conserving historic works of art taking note of practices across the globe of those whom have been custodians of stained glass for hundreds of years longer than us.
Although it requires a craftsman with many years of experience and education to fully understand the functions of each component contained in a stained glass window, some of the symptomatic clues can be easy to spot if you know what you are looking for. We recommend windows be visually inspected periodically to determine the health of the systems and when and if maintenance will be required. We offer this service at no charge. We engage our customers in maintenance programs that will be much more cost effective long term when you can rectify a problem before it accelerates to a stage that will require extensive intervention and avoidable permanent damage.
Like all building materials, those contained in stained glass require maintenance. Unlike most disposable architectural materials in use today, leaded glass has the ability to be brought back to life and repaired. There are relics of stained and leaded glass dating back to the seventh century. In Europe, you can find stained glass hundreds of years old still containing original lead.
Beginning with the most common and first stage of deterioration is leadlight cement. As the cement begins to decompose it dries out on the surface and loses its patina, appearing chalky. See Figure 1. Advanced stages of cement loss can be noticed as a loose and chatter sound if the windows are gently tapped with your finger. It is also possible to see the cement becoming dislodged and falling out of the lead came.
Lead failure can be indicated by broken solder joints or fractures in the lead came. Broken joints can be re-soldered, see Figure 2. Fractures not near a joint cannot be mended with solder and need to be replaced with new lead, see Figure3. Either of these problems can be the result of excessive movement due to cement loss, inadequate support or structural movement.
Broken glass will be the most visually noticeable problem to identify. As we all know, glass cannot sustain particular forms of physical impact. Even in a well constructed system of flexible lead and cement that absorbs most of the force, fracture is possible. The most common location for glass fracture is where a panel features a horizontal lead line extending almost entirely across the panel. When support systems (including cement) fatigue, the panel will begin to "hinge" on these lines, glass panes that do not share the horizontal line can be broken.
Some support system failure can be obvious, see Figure 4. Other times it may not be as apparent until damage has already occurred. Evaluation of this component takes a trained professional to compare the factors working against the panels and how much reinforcement is required to defend against them.
Problems associated with protective glazing can take decades to visually display themselves. Ventilation of protective glazing is usually achieved through small, round metal vents drilled and set into the glass preferably on the top and bottom of each pane. Lack of ventilation can result in extremely high temperatures which will rapidly decrease the lifespan of all building materials it encapsulates.
click on image to expand and view captions