Stained glass is a flexible network of glass, lead, solder, cement and supports. Over time, that network can move out of plane. Bowing is not merely cosmetic; it changes how loads travel through the panel and can increase the risk of cracks or collapse.
Common contributors to bowing
Lead becomes fatigued, cement loosens, support ties fail and large panels continue to carry their own weight. Heat differentials, wind pressure, poor exterior coverings and movement in the surrounding frame can add stress.
- Lead fatigue
- Failed support bars or ties
- Loose cement
- Heat buildup
- Frame movement
- Oversized unsupported sections
Signs the condition is progressing
A panel that appears wavy from one angle may be significantly displaced when viewed from the side. New cracks, rattling, open joints and daylight at the edges can indicate that movement is continuing.
Why pushing a panel flat is not a repair
Applying force without understanding the lead and glass can create additional breakage. Stabilization, removal or restoration should be based on condition, access and the structure of the complete window.
