Preserving Stained Glass

by Emily Kozlowski

St. Louis is built of brick — and glass. With the abundance of churches, this city has a fantastic supply of stained glass windows. I recently attended the session on identifying and preserving stained glass at the Missouri Preservation Conference. The talk was given by Stephen Frei of Emil Frei and Associates. The company was founded in 1891 by his Bavarian great-grandfather Emil and has been run by the family ever since. They are the leading provider of stained glass in St. Louis most definitely, but are also largely important to the Midwest as well.

I was struck by the beginning statement of his presentation. Stephen said that he was devoted to creating beautiful and quality stained glass because it is an art that affects generations. A stained glass window reaches communities throughout decades. The glass is long lasting in itself but can be kept even longer with informed preservation techniques. The following is what I learned and had never given much thought to until now.

A stained glass window is hand painted, piece by piece. Emil Frei and Associates paints with metals, never organics. This ensures that the color stays vibrant and will not fade as organic material is bound to do. The painters are chemists in a way. Each color is a different chemical substance that may fire into a different color or not be compatible next to a different color. It is a very knowledgeable art.

Emil Frei and Associates works in the traditional technique of glass blowing, the way the founder learned in 19th century Europe. The Industrial Revolution brought about rolled glass, a modern technique. The difference being that it is rolled out into its form on a flat surface, rather than letting gravity and breath shape it. The cathedrals a tourist might visit in Europe have blown glass windows, which speaks to the longevity this technique offers.

If you are looking to preserve your own stained glass, the first thing to do is not clean it excessively. Since a window is placed between a warm interior and the cold outside, condensation naturally cleans it of any dust or incense residue inside a church. It only needs to be cleaned by hand every 40-50 years. If you are determined to clean it, tap water is the best thing to use. Distilled water has the chance to remove color because it can permeate the glass, whereas tap water can’t. One of the most important things to know in its preservation is the manufacturer of your window. The chemicals they used or the process of glass making can determine how to clean it. Restoration is also dependent on this knowledge. If stained glass is shattered, you should keep the pieces so that an expert can accurately identify and recreate the chemical components and appearance. Lastly, understand the importance of lateral steel bars. They are thin, black rods placed every certain number of feet onto the window. They are minuscule to the overall design and are necessary to prevent bulging in the window.

Our built environment is an extraordinary source of history through architectural styles, the way buildings were used, the people who inhabited them, etc. Stained glass windows are pictorial histories that tell a story upon first glance. They are long living and thus were created because their design/story were deemed important enough for generations to come. I can remember a large stained glass window in a stairway in the Tower Grove house I grew up in, and I wonder how many other St. Louis homes have them. There may be many to be seen, but our churches offer a good starting tour.

Emily Kozlowski, an art history major at Webster University, is a Research Intern at the Preservation Research Office.