9 Important Facts about Glazing Windows

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Although it sounds like a process of applying some sort of treatment to your windows, glazing actually means applying putty around the edges of the glass. The name comes from the putty, or glaze, that binds the window frame to the window pane.

Glazing is a crucial part of effective maintenance. Without glazing, your aging windows can begin to leak, which can cause water damage to the window frame and other parts of the home’s structure.

1. Glazing Improves Efficiency

Glazing windows adds insulative qualities to the glass by limiting the amount of air that can seep through. A solid glazing job will reduce heating and cooling costs by helping your home better retain its internal temperature.

hands using a putty knife to glaze caulking on old window

2. Glazing Improves Integrity

Pulling together the pieces to create a solid unit makes the entire window more stable. Glazing reinforces the edges of the glass along with the pane. Without glazing, the glass can leak or even fall out of the frame, so the putty is a critical component.

3. Glazing Takes Some Abuse

Being constantly exposed to the hot and cold temperatures, and the abuse from wind, rain, sleet, and snow, glazing is bound to wear down. Over time it can dry out, crack, and fall out of the window. The good news is that it can last decades without repair if it's properly applied.

4. Glazing Can be Done Anywhere

It’s possible to glaze your window without removing it, but it’s easier and more efficient to remove it. This allows you to lay it flat while you work.

hand using a putty knife to apply caulk on a wooden window frame

5. Not all Windows are Equal

There are three types of windows commonly used in residential homes:

Single Pane - Single pane windows consist of a single pane set into a rigid frame, and as a result, have very low insulation properties. Single pane glazing windows are no longer the popular choice due to the rising costs for energy and the availability of more efficient designs. Partly because of these weaknesses, single pane windows are the most likely to need glazing.

Double Pane - Double pane windows have two panes of glass with a layer of inert gas sandwiched in between. This gas creates a hermetically sealed environment, meaning the interior of the window is isolated from the exterior. Extra glazing on these windows provides the highest insulation value, but comes with the disadvantage of increased cost and weight.

Triple Pane - As you might expect, these windows have three panes. Like double pane models, they contain an insulating gas, usually krypton (the major export, as we know, of Superman's home planet).

6. Putty Needs a Massage

Glazing putty is a little like Play-doh. It’s malleable, but only if it’s worked a bit. Manipulate the putty in your hands awhile, warming it until it becomes soft and easy to roll in your fingers.

7. Your Putty Knife Needs Sanding

A glazing knife is a great tool for the task, but really any 1” to 11/2” putty knife will work fine. The key is to make sure the putty knife is completely smooth and free of debris. An easy way to ensure this is to sand it down. This will help it flow across the sealant without any snags.

putty knife with putty on wood

8. There’s More than One Application Method

The good news for the glazing newbie is there isn’t one “right” way to tackle the job. The most common method is to make a rope or snake shape with a ball of putty. Roll it between your hands until a long-thin rope-like strand becomes long enough to cover the length of one side of the window. Then press it into place making sure to firmly set it into the glazing space.

The second method is to use your putty knife to press putty into the glazing space one piece at a time, working your way around the frame.

9. The Putty Knife is the Primary Tool

The putty knife does 95% of the work here. Once the putty is in place, drag the putty knife down the strip to create a flat face. Hold the putty knife at about a 45 degree angle from the outer edge of the frame to where it meets the glass.

While pressing down, allow the edge of the putty knife to cut the excess putty off. You should have a lot of excess. Just put it back in the glob of putty in your hand and work it back in for the next section of window. Also use the corner of the knife to smooth out the corners of your glaze for a uniform look around the window.