The way a stained glass repair is approached depends primarily on two things. The first is the location, size, and degree of damage. The second is whether the stained glass was constructed using lead came or copper foil. If the stained glass has suffered only a minor crack that is visually apparent but doesn’t threaten structural integrity, it’s possible to use a crafted illusion to cover the crack in such a way that the design isn’t negatively affected. If the stained glass repair involves multiple cracks or if the glass itself has buckled, the repair is more extensive but can still be managed with a little know-how.
Making a minor stained glass repair by covering a hairline crack or minor break involves copper foil, solder, and a soldering iron. This method works best on a copper foil type of stained glass because the repair will fit right in with the other strands of soldered copper foil that hold the mosaic of glass shapes together. A piece of copper foil is laid along the length of the crack, covering both the front and back sides of the glass to give the illusion that the repair is an intended copper joint. The copper foil must meet the soldered foil strips at both ends. With the soldering iron, a line of solder is run along the copper foil on both sides.
If the damage is more extensive or if the piece is constructed of lead came, the stained glass repair becomes more complex. First, using a hack saw, the zinc border is removed from the edges of the broken glass. Protective breathing masks and goggles are a must as this process could be a little dangerous. The glass is placed onto tracing paper, and the outer edge is traced, marking where the zinc has been cut onto the paper. This will be used to reconstruct the panel and keep it properly squared.
Next, the zinc is heated on both sides of the glass and wiggled with pliers until it is loose enough to remove. Once the zinc border is removed, the broken pieces are sliced further with a glass cutter. Solder is melted between the broken piece and an intact piece. By tracing the tip of the soldering iron along the unbroken piece, the edge is cleaned. Then, a glass cutter is used to trace replacement glass to the correct size and shape, and it is cut and ground to match the broken piece.
As each broken piece is replaced with an intact substitute, the stained glass panel must be checked to ensure that it is squaring up correctly. The lead came is replaced as needed, the effected joints are soldered, and the came is puttied to secure the glass. If the art glass piece is elaborate or if the damage is extensive, it might be worth considering professional stained glass repair.