Are Your Stained Glass Windows Failing You ?
Stained glass windows are often the crowning glory of a sacred space . Serving the dual purpose of art and architecture , they augment and enhance a space like few other architectural assets . Yet , for all their beauty , their primary purpose is to protect people from the elements . When windows start to bend or leak due to broken joints or cracked glass , most people notice the damage and call a specialist for help . What many people often miss is another key element — lead .
In fact , what is often referred to as “ stained glass ” is in truth “ leaded art glass .” The stain refers to a specific technique : silver nitrate that actually stains the glass surface various hues of yellow . Other colors are provided by the glass itself , as well as applied paint or enamel . Simply put , most stained glass is leaded glass ; but not all leaded glass is stained . Although the glass design is what people think of first , strips of lead “ came ” provide the structure and hold the individual glass pieces together . Both the glass and the lead are relatively inert in a newly created panel , so unless you touch the lead and fail to wash your hands afterwards , you can safely enjoy your windows .
by Ariana Makau
President , Nzilani Glass Conservation
Being around old stained glass — or repairing it — is a completely different matter . Lead oxidizes over time , creating a whitish grey powder on the surface . The powder can disperse from the windows onto sills , pews or tables in social halls and schools . It is often hard to distinguish from “ normal ” dirt or dust . Additionally , windows are set into the building with other materials : wooden stops , border putty , cement acting as stone set , or aluminum frames to name a few . Wherever these materials intersect , those areas also become lead-contaminated .
Ariana Makau in full PPE ( personal protective equipment ) removing an old , oxidized , stained glass window at St . Vincent de Paul in San Francisco , California . Photo : Nzilani Glass Conservation
Of course leaded glass windows add great value to the building — both historically and monetarily . Correctly preserving older windows is the right thing to do — albeit under correct health and safety precautions . Site work should always be undertaken by a leaded glass specialist who also has certified lead worker training .
Contrary to what many people believe , the highest exposure occurs when leaded windows are being removed , not when they are being repaired under the controlled conditions of an art studio . The work area should be contained , ( i . e ., separated ) from the public — especially where children are present . If you can
14 SACRED PLACES • WINTER 2021