Learn How to Replace It With Historically Accurate Restoration Glass®

thanks to Renee Rosiak & Bendheim for this submission

Owners of historic homes and buildings take great pride in their antique window glass. With its occasional wave, bubble, and characteristic imperfections, it testifies to the history of an old structure or a piece of furniture, exuding the charm and character of by-gone days.

The making of window glass began in the 7th century with the development of mouthblown Crown glass. The 11th century saw the invention of the Cylinder glass method of producing mouth-blown antique window glass, first developed in Germany. Today, Cylinder and Crown glass are two types of authentic, mouthblown antique window glass found in fine American homes and buildings built from the 17th to early 20th centuries.

When old window glass is broken or damaged, people often go to great lengths to find a perfect match in order to preserve the historical integrity of a home or building. Finding the right glass can pose a significant challenge, considering the relatively wide-spread production of antique window glass ended after the invention of the first mechanical method for “drawing” glass, to be later followed by today’s ubiquitous “float” glass.

Window glass salvaged from another old building can be one replacement option. However, it can often be challenging to remove it from its old frame, cut it to the required size, and clean it.

An excellent alternative is to purchase cut-to-size “new antique” window glass made today utilizing the same techniques and tools used to make mouth-blown glass centuries ago. Authentic Restoration Glass®, produced at Germany’s Glashütte Lamberts, is crafted by skilled glass masters. The factory has preserved the mouthblown production methods through generations, guaranteeing the historic accuracy of this glass. As a testament to its authenticity, Restoration Glass is found in our country’s most prestigious restorations, including the White House, George Washington’s Mount Vernon home, and Thomas Jefferson’s Monticello.

view through regular glass window with no restoration

view through Light Restoration Glass® window

view through Full Restoration Glass® window

To match precisely the original structure’s time period or the desired glass appearance, homeowners can select one of two varieties of Restoration Glass – “Full” or “Light.”

Full Restoration Glass is more distorting and accurately represents antique window glass made in the 17th and 18th centuries. Its distinct, somewhat “wavy” appearance makes it an excellent choice for colonial-style windows, antique and reproduction furniture.

Light Restoration Glass is less distorting and is an excellent match for glass found in structures built in the 19th and early 20th centuries. Its slight distortion is more pronounced when viewed from a distance, in reflected light, and over a large area, making it ideal for use in windows and doors.

If uncertain about the appropriate amount of distortion, homeowners can request samples from Bendheim or send a piece of the original glass to the company to determine the best possible match.

“New antique” window glass offers additional advantages to homeowners by blending historically accurate aesthetics with modern capabilities and standards. Today, Restoration Glass can be laminated with a special resin interlayer to provide an impact-resistant safety glass, which will remain in place if broken, as well as provide enhanced sound control. Current building codes require safety glass to be installed in doors and sidelites, among others.

To restore a damaged old window and replace its broken glass, homeowners can hire a glass installation professional or do it themselves. Those with the skill to complete the installation on their own will benefit from the following tools: protective gloves and goggles,  heat gun, putty knife, glass cutter, framer’s point gun, pliers, primer or shellac, glazier’s points, Calcium Carbonate (“whiting”), paint brush, and paint.

The steps below and an instructional video (featuring the restoration of Martha Stewart’s 1805 farmhouse window) will demonstrate how to replace broken antique window glass.

• Safety first. Put your protective gear on.
• Remove the window sash and place it on a table or other flat surface.
• With a heat gun, warm and soften the old putty so that it can be easily removed. Be careful not to burn the wooden sash.
• Remove the old putty with a putty knife, taking care not to damage the frame.
• Cleaning out the putty will expose the old glazier’s points. Pry the glazier’s points up.
• Run the glass cutter diagonally over the glass pane twice creating an X.
• Gently tap the glass from underneath to break it into pieces that can be easily removed.
• Remove the old glazier’s points with pliers.
• Clean and scrape out the remainder of the old putty from the cleared glass channel.
• After ensuring the window surface is dry, paint the channel with a primer or shellac. Note that regular primer dries in approximately two hours; shellac dries in approximately 10-15 minutes.
• After the primer or shellac is dry, place new putty inside the channel.
• Gently press a new glass piece into the opening. Squeeze the putty down by carefully applying even pressure on all four sides of the glass, ensuring a snug fit.
• Use a framer’s point gun or a putty knife to install one or more glazier’s points in each of the four sides of the opening. The glazier’s points will secure the glass in place.
• When using the putty knife, gently rock the glazier’s points back and forth until they are properly seated in place.
• Press more putty around the edges of the glass panel.
• Using the putty knife, flatten the putty to ensure a snug fit.
• Place the putty knife at a slight angle in one corner of the glass and run the knife along the side to remove extra putty. Repeat on all four sides.
• Take a small amount of “whiting” and spread it on the glass. Use a soft brush to rub the whiting on the glass and putty to remove excess oils, then gently clean it off.
• Wait approximately two weeks for the putty to dry before re-painting the window.

Good luck with your restoration project! Please view the instructional video at www.restorationglass.com for additional tips and information.