If your historic house or building contains original stained or decorative glass, it probably shows signs of wear and tear. Because stained and decorative glass was used to add style and artistic flare, it was typically placed in the most public and visible locations of a historic structure. These public areas often exposed the glass to sunlight, rain, sleet and snow. Exposure to the elements can slowly deteriorate the glass. However, this deterioration can be reversed with regular maintenance and repair.

Identify Your Decorative Glass

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An original 1902 stained glass window in great condition. Source: Bob Yapp

Your historic house or building may contain any of the types of historic decorative glass described below:

Stained Glass. Stained glass is not actually stained at all — it is dyed. This type of glass does not have a stained pigment. Stained glass is made by adding metallic oxides to silica sand and pot ash, such as iron for greens and copper for light blues. Colored glass has traditionally been set in lead caming, or installed in divided-light (multiple-paned) windows and door sashes with a standard wood muntin.

Before and after 1900, Louis Comfort Tiffany and others perfected the process of creating a type of stained glass called opalescent glass. John Triggs, owner of the Youghiogheny Opalescent Glass Company in Connellsville, Pennsylvania, describes opalescent glass this way, “Making opalescent glass is the art of creating a quality that is not completely transparent. The glass is translucent and shows the variations in color that create a play of light."

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An original leaded and beveled glass transom window. Source: Bob Yapp

Beveled Glass. Beveled glass was used extensively in doors and windows in historic houses and buildings throughout Wisconsin. It was also very common in mirrors. Beveled glass is made by using an abrasive process to cut the edge of a piece of glass at an angle. After the edge is cut, it is polished. Beveled glass has traditionally been set in either lead caming or wood muntins and can still be purchased today.

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This door and transom have an acid-etched letter and address. Source: Bob Yapp

Acid Etched and Sand Blasted Glass. Acid etching and sand blasting are both techniques in which a design is made by removing specific areas from a sheet of glass. Both of these techniques are still being used today.

Acid-etched glass is created by coating the sheet of glass with wax and then scribing out a design. The designer applies hydrofluoric acid over the scribed design, and the acid eats away at the glass but not the wax coating.

Glass sand blasting was invented in 1870 by an American named Benjamin Tilghman. To sand blast a design into glass, the designer lays a resistance film, not unlike contact paper, on the glass. Then the designer blasts the cutout design portions with sand and pressurized air.

Maintain Your Decorative Glass

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Installing grout into the lead caming of a historic window is an easy and inexpensive way to maintain these character-defining windows. Source: Bob Yapp

You can maintain your stained and decorative glass without hiring a professional or purchasing expensive materials or supplies. To maintain your glass, you need to do two things regularly:

• Keep the glass and lead caming clean
• Re-grout the gaps between the lead caming and the glass

Re-grouting is necessary because grout can become brittle over time and eventually fail. If you need to re-grout the lead caming in your glass, you can buy dry grout powder mix from any decorative glass shop. Follow these steps to re-grout the lead caming in your stained or decorative glass:

1. Use a toothpick to pick out the old grout.
2. Prepare the grout mixture by adding the dry powder to a solution of two parts turpentine and one part boiled linseed oil. Mix it until it is the consistency of pancake batter.
3. Use a wooden dowel, sharpened like a pencil, to draw the grout along the lead caming.
4. Use a plastic putty knife to pack the grout mixture into the joint between the caming and glass.
5. Clean off the excess grout by rubbing the glass with sawdust and a cotton cloth.

Repair Your Decorative Glass

Your older stained and decorative glass might need any of these typical repairs:

• Replacing broken glass
• Replacing failed lead caming
• Soldering the lead caming

If your glass needs any of these repairs, you should hire a professional stained or decorative glass repair person.

The information presented here is not intended to provide comprehensive technical advice or instructions on solving historic preservation issues. Any information contained or referenced is meant to provide a basic understanding of historic preservation practices. Read full disclaimer.