In the previous two videos in the wood window repair series we outlined techniques for safely removing the upper and lower sash of the windows in a Historic home. The 3rd video in the series provides window glazing tricks so you can properly remove and replace the glass. The following window glazing tricks demonstrate the proper technique for removing the old glazing, repairing the wood sash, and reinstalling the glass and new glazing.
Strip the Old Paint
Before you can properly inspect and repair the window sash, you must first strip the old paint. Use a heat gun to assist in the removal of the existing paint. By applying heat to the surface and using a putty knife or paint scrapper, the old paint will easily lift off the wood surface. Conversely; you would spend hours and a ton of elbow grease trying to sand off the old paint. Call me lazy if you like, but I believe the smarter method is to make use of the heat gun.
With the paint removed you can do a thorough inspection of the wood sash. Fill any minor cracks and crevices with wood filler. Be sure to pay close attention to the muntin’s. Taking the extra time to refurbish the wood sash will preserve the old wood and extend the life of your windows for decades to come. Apply a coat of high-quality primer to the wood sash before moving on to the glazing step.
Window Glazing Tricks
Many older windows have a channel in the bottom of the sash. In this case, you need to place a small bead of glazing putty in the bottom of the channel. This will help to prevent the window from rattling. Roll a thin strip of putty between the palms of your hands and lay it in the bottom of the channel. Be sure to fill the entire length of the channel. Don’t overfill it as you need to leave enough room for the glass itself. You want just enough putty that it will ooze out when the glass is placed into the sash.
Place a layer of glazing on the remaining 3 sides of the sash. The term for this step is “back bedding” which makes sense as you are creating a bed of glazing to seal the back side of the glass. Roll a large ball of glazing in your hands to warm it up which will make it more pliable easier to apply. Holding the ball between your thumb and index finger, push the glazing into the sash rabbit using a twisting action. You should end up with a 45-degree layer of glazing which fills the rabbit. The glass itself is dimensionally undersized to allow room for expansion and contraction. A generous application of glazing is required to fill this void.
With a bed of glazing in place you can go ahead and place the glass into the sill. You should wear a pair of leather palm gloves to protect your skin. Grab the top of the glass as you raise it vertically. When you start to lay the glass down, place one hand in the middle of the glass to reduce deflection, and reduce the chance of the glass breaking under its own weight. With the glass in the horizontal position gently press it into the lower rabbit (channel). Lift the sash to the vertical position to further push the glass into the rabbit until the glazing oozes out along the entire length. For larger panels of glass this step is best completed with 2 people.
With the glass seated in the bottom channel you can lay the sash back down into the horizontal position. Gently push the glass into the glazing around the entire perimeter of the sash. When you see the glazing oozing out you can secure the glass by installing the metal glazing points. Using a putty knife, cover the glazing points and fill the void around the edge of the glass with a liberal amount of glazing putty. Push the glazing into the void, leaving a consistent 45-degree bead around the entire perimeter of the sash. Your window sash is as good as new and ready to be reassembled.