Carefully remove the old window. If it is cracked, criss-cross it with masking tape. While wearing safety goggles and gloves, tap the glass with the rubber mallet or hammer.
Get out the old, gunky putty from around the frame. You can use the putty knife or a scraper to do that. You can make sure it is all out by using linseed oil on the tough spots. Let the oil soak before scraping out the old putty. Also, be sure not to bend the window frame while scraping or your new glass won’t fit in it.
Put more linseed oil around the wood so that the new putty doesn’t dry out too fast. While you are doing this, you can take out any old, metal spring clips. They should be in the corners of the frames.
Measure the new glass window by using the dimensions inside the frame. You want the glass to fit inside the frame by making it 1/8 or 1/16 smaller. The difference will make the glass fit better even if the frame isn’t perfect or the cut isn’t exact. Cut the glass with a double-strength glass cut.
Roll the putty into a shape that will line the frame of the window pane. Think of it as a snake ready to eat your new cut glass. Tuck the clay into the frame using the putty knife and install the metal clips every six inches or so. They will help keep the glass in place when you set it.
Carefully set your fresh cut glass window into the clay and frame. If you need to get more support to hold it in place, add more clips to the glass. You can use the putty knife to help get the glass into the corners or clips. Make sure that the glass is pressed hard enough to push out any air bubbles.
Put more of the clay around the pane on both sides where the glass meets the frame. Press it all around and then cut the excess off with a putty knife by placing it at an angle between the frame and the glass.
Scrape off the rest of the excess putty using a scraper. If it is too sticky to come off, use the linseed oil on the scraper and try it again. Let the glass window dry for three days before painting.
Fact BoxThings you'll need
¯spring clips or glazier’s points
¯rubber mallet or hammer