Monday, June 14, 2010

Hmmm, Glazing, Yum

No, not that kind of glazing. I'm talking window glazing putty. That nasty crumbly stuff on the outside of old windows that is supposed to be holding the glass in but really is just catching dirt and rain and making your house look trashy. My first battle with ancient glazing putty was in CA with ten, yes ten, double hung windows in the back bedroom that were painted shut but somehow still rattled in wind -it was the glass moving in the frame since there was very little putty to hold the glass tight. In truth, little metal pieces called glazier's points are what actually hold the glass in, the glazing putty is there to help the window shed water and to make the sash look nice. There's also a term "double glazing" which means there are two panes of glass but that is usually held in the sash (or frame) by trim, being metal, vinyl or wood. The great thing about a single glazed window is that if it breaks, it's easy to fix, just pull out the broken glass and the old putty and install a new sheet of glass with glazing points and reputty the outside. I haven't figured out how to fix a broken double glazed window pane yet. During Hurricane Ike, only one window in our house cracked, the double glazed bathroom window. The 90 year old glass in the rest of the house held up fine. I just left it cracked. So many years ago when I was rehabbing the ten windows, I had to figure out how to reglaze windows. Dap makes a great product that I now use after experimenting with other glazing putty products. This product comes in a caulking tube and is dispensed using a caulking gun. Someone really skilled, in theory, should be able to lay the putty in perfectly right from the tube with no need to model it at all. After reglazing over 30 windows in the last 9 years I still need to work the putty once it's applied. There's another product that comes in a quart paint tin that I found hard to use, you have to work it into a thick rope with your hands then press it into the glazing channel. I didn't like it and have used the Dap glazing caulk ever since.

Our current house has all double glazed windows but I found myself restoring a very old door to use on the chicken coop that had a glass 12 light panel inset. Most of the glazing putty was gone but thankfully the glass panes were not broken. The old style glazing points, which are either diamond or triangle in shape and flat, sharp metal were mostly still holding the glass in but I did put in some new
glazier's points just to be sure. One of the most important things when reglazing a window, which can be done with the window sash still installed on the house, is to remove all of the accumulated dirt in the glazing channel so when primed, it sticks and seals. Here's the simple steps to reglazing a window: 1) remove all of the loose, old glazing putty, being careful not to chip the glass. Do the whole window once, take a break then come back to it and you'll find more loose stuff. Remove it all. Any that seems really secure can be left, usually the top edge of the glass since this rarely sees water damage. 2) clean out the dirt and crumbles of putty. This can be a challenge along the bottom edge that gets the most wear. I'll scrape it then go back with a small wire brush to loosen the dirt. Vacuum up the dirt dust and debris with a shop vac, making sure the whole channel is clean. Do not use water to clean unpainted wood. 3) paint primer in the channel where the putty will go. I usually prime the whole window at this point. Don't worry about getting primer on the glass, it'll scrape off later.
4) apply the glazing putty or caulk. Be patient! I use a tool (in the picture) to smooth the putty to a nice angle that will shed water. Use a wet finger to smooth where the tool overlaps the putty and creates a bump or drag mark. Leave any excess putty on the window as long as it's not touching the glazing putty that was just applied. It'll harden and be scraped off later. 5) after about 3 days, the glazing putty is hardened so it can be trimmed if needed, like if there's a bump or tool mark. Use a sharp razor blade for this. A sharp box cutter held at an angle also works but keep enough material to ensure shedding of water. Once satisfied with how it looks, it can then be painted with the top coat. I've had situations where I forgot to paint the window after the new glazing putty is in and it makes more work since you then have to clean what you applied of the dirt and dust collected on it before painting (it stays a little tacky so it collects dirt fast).

With a little practice and development of technique, the exterior of vintage windows can look new and be more efficient, or new life can be given to an old door headed for the scrap pile.

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