Cleaning Stained Glass Windows
Cleaning Stained Glass Windows
Stained glass windows looking a little dirty? Before you try cleaning them yourself—read this article. If cleaned improperly, you might accidentally do more harm than good.
All stained glass windows will become dirty over a period of time. They will collect dust, and smoke from candles. Often, the oxidation powder from the lead and the powdering glazing compound that holds each piece of glass in the lead will leach to the interior surface. Under most circumstances, professional stained glass conservators will recommend that stained glass windows should be lightly dusted to remove any surface accumulation of dirt, while the outside of the windows, if not covered with protective coverings, will be cleaned by the weather from time to time. However, more extensive cleaning of the interior surface can become complicated.
When stained glass is painted, the paint is always applied to the inner surface of the window to keep it from the elements. This "paint" is really ground glass with a high lead content to lower its melting point, mixed with metal oxides... similar to glaze on a piece of pottery. It is applied by brush in a series of steps by a professional glass artist; then the glass is kiln fired to temperatures around one thousand degrees. Unfortunately, exact temperature monitoring was not entirely practical in old-time studio kilns and some painted areas did not properly become a permanent part of the glass. This means the paint can be unstable and can be easily removed—even by gentle dusting.
Because of this, an unknowing person could inadvertently erase special shading and lines from the glass. Some well-meaning people have "cleaned" windows so well that they removed what they thought was "dirt" ...and subsequently ruined the windows by removing the paintwork. So, it's very important that cleaning the interior surface of stained glass windows is done in a very mild and non-abrasive way, especially if the interior surface has painted glasses.
First, try washing the interior glass with a soft, clean cloth and distilled water. Distilled water is better than tap water because it contains no impurities. Take the cloth, dip it into the distilled water, wring out all excess moisture and gently dust the interior surface. If it appears that any glass paint is being removed, stop immediately! Any further cleaning will have to be done by a professional studio. If the interior surface of the window does not have painted areas, the glass can be scrubbed a bit more aggressively, and, in the case of dirt in textured areas, a soft toothbrush can be used (but only on non-painted areas). Moisture should be limited.
In some Tiffany and "Tiffany style" windows, multiple glass layers (plates) are joined together, and dirt can accumulate under these plates. The cleaning in these areas is a project for well-trained stained glass professionals only! Do not attempt to clean plated areas, as moisture around these areas can only make them worse.
Willet Hauser is a stained glass window firm with over a century of stained glass design, repair, and restoration experience. Each year, we work with hundreds of churches and other institutions to design beautiful new glass windows or to repair, restore, and protect their existing treasures.Contact Willet Hauser Architectural Glass