How to glaze a window

What is glazing a window?

 When you hear the phrase “Window Glazing”, it actually has two meanings – glazing as the window glass itself and glazing that refers to the glazing compound used to hold the glass in place. In the most general sense, glazing is used as a broad term that refers to installing new glass panes.

Before knowing how to glaze a windowpane there are 3 main types.

Window glazing types

1. Single glazed window

Windows that have only a single sheet of glass. Outdated, inexpensive, and the least energy efficient.

2. Double glazed window

Windows with two layers of glass with a space in between that house an insulating agent such as argon gas.

This is the most common type of modern glazing for thermal and sound insulation.

3. Triple glazed glass

Windows with 3 sheets of glass and argon gas in between each gap. This is the least common, best insulated, and most expensive type of glazing.

Generally used in rooms facing a loud highway to reduce noise transmission.

What causes broken window seals?

Before we look into how to glaze a window, let’s find out why you need to glaze a window.

The primary function of a window seal is to keep humidity and the draft out. In the case of double and triple glazed windows, a broken seal causes humid air to seep through, resulting in fogging or worse.

Causes of seal failure:

• Gradual wear and tear due to ‘Solar Pumping’ which can constantly expand and contract the panes. Escalated by windows that receive the most direct sunlight.
• Faulty window installation causes unnecessary extra pressure on the pane edges.
• Sealant damage is caused by prolonged exposure to heat [1] and heat guns used to work on window frames.
• Sealant damage due to chemical cleaners such as paint strippers.
• Windows that are constantly buffeted by strong winds. 

What happens when window seals are broken?

• Visible condensation – While temperature fluctuations brought about by changing seasons can occasionally cause fogging, a  broken seal [2] means that insulation is compromised, thus almost always developing condensation regardless of the climate. 
• Distortion – Broken seals cause the argon gas to leak, sometimes causing a small structural collapse in the panes. The panes can also crack despite no sign of external damage.

Window glaze putty vs culk

#1 Glazing putty

Sealing material that’s usually a combination of linseed oil with either chalk, calcium carbonate powder, or polybutene. The highly moldable material is perfect for sealing windows around a wooden frame.

Putty needs time to fully cure and harden, but lasts indefinitely once it does, making it highly efficient. The only real drawback here is that glazing putty is limited to just glazing applications.

#2 Caulk

Consider window glazing in a tube with caulk for a quick fix.

Waterproof material used to prevent air and water leaks. Given its natural tolerances, caulk is most commonly used in plumbing applications and acts as a gap-filler or when installing and glazing a window in a door or window.

Made of silicone or as a latex window glazing in a tube, caulk is more versatile than putty but is less-lived. While putty stays after fully curing, you might need to re-apply or apply a new type of caulk every 10 years or so.

Steps in glazing a new window pane

The steps below apply to double glazed windows as the single glaze is now considered obsolete and inefficient.

Tools and materials needed

Here’s what you need when prepping a window for glazing:

• Tape measure 
• Knife/chisel
• Glazing putty
• Putty knife
• Heat gun
• Pliers
• Epoxy
• Power sander
• Paint and applicator
• Jigsaw with glass cutting blade (optional) 

Here’s how to glaze a window with putty

Step 1. Perform an inspection

This is the time to also look for and isolate any major cracks and distortions along the panes. 

Before actual glazing, inspect the entire exterior of your chosen window.

Step 2. Remove the sash

This is the part of your window that shuts and opens. The sash is a long, slim piece of wood or metal usually found on the outer part of a window’s interior. 

You’ll need to remove the screws on the windows that have stopped. Use a sharp knife or a chisel’s sharp cutting edge to gently cut the paint line first. 

Step 3. Removing old or damaged glazing

Now that you have access to the panes, it’s time to scour the window for any damaged glazing. Remove damaged panes of glass to be replaced with a new panel of glass.

• Use a hammer or gloves to remove and break up the glazing into smaller pieces if it’s already broken.
• Use a heat gun or slowly pry out the glazing.
• Excess heat might need you to scrape the paint and repaint the surrounding window frame.

Step 4. Inspecting the wooden frame.

Once stripped of glazing, it’s now time to check the frame and patch it up for any damage.

• Fill out cracks using two-part epoxy. 
• Shape and sand out material to smoothen and prep if a new finish is needed. 
• Apply an undercoat and a top coat of paint in the recess.

Step 5. Glass installation

Reinstalling or replacing the glass panes.

To get the best fit, measure both sides of the frame’s opening and deduct to ⅛”. 

• Cut or have your local hardware expert cut new replacement panes if needed, based on your measurements. 
• Add some glazing compound to the frame and press the glass against it.
• Hold it with a set of new glazier’s points and push the clips into the frame using a putty knife.

Step 6. Applying the glazing putty

Use the putty to seal off the newly installed glass panes and finish the window. Be sure to work at room temperatures for best results.

• Take about a golf ball’s worth of putty and ‘knead’ it in your hands until it becomes pliable. 
• Roll it out and mold it along the corner of the windowpane
• Take the putty knife and push the glazing into the frame and glass.
• Smoothen out any excess with either the putty knife or the flat end of a chisel. 

Step 7. Optional coating 

After allowing the putty to fully cure, for around 72hrs to be sure, you can coat it in oil-based primer for an additional layer of protection.

While you can opt not to paint, this method also helps extend the glazing’s longevity. 

How to alter frame for bigger glass pieces?

Essentially, you’ll need to 1st measure the dimensions of the frame you wish to alter. Once you have that, next is to decide on the size of the glass you wish to install.

If you plan on putting in glass bigger than the original frame, (To recycle come glass you already have). Then first you’ll need to dismantle the frame, take out the beading, and custom-cut certain pieces to be able to fit the new pane/s.

On simple frames, you can use a wood router and a chisel to carve out or enlarge existing grooves to be able to fit a larger glass panel.

Tips for removing and reinstalling window beads

• Beading is usually mitered at 45°. 
• Remove beading by shanking a sharp knife near or on its edge. Pull it out, making sure that it comes off as a whole. 
• Clean and prepare the exposed bead area for a fresh install. 
• Triple check measures before proceeding to cut new beading pieces. 
• Remove and always apply fresh glazing for replacement projects older than 5 years. 
• Prime exterior beading to maintain aesthetic and offer added resistance to weather conditions.

Dos and don’ts for glazing a window

Do do this

• Do select at least dual glazed windows if you need better insulation as they are considered the modern standard.
• Do keep in mind your home’s layout and design. It helps in selecting corresponding window designs and in identifying key placement locations. 
• Do observe proper installation and follow tight-fit measurements. This will prolong glazing lifespan and effectiveness.

Don’t do this

• Don’t always opt for single glazed windows as they are considered obsolete and are inefficient even if they are more affordable. 
• Don’t paint over or tamper with windows with freshly applied glazing. 

Safety practices for window glazing.

• Always wear safety goggles around broken glass.
• When handling the glass, it’s best to always put on gloves.
• Handle the glass pieces with care. Ensure that there is enough room to not hit against anything and don’t place them directly on hard surfaces. 
• Carry glass one piece at a time and cover it with a blanket or towel to cushion them and protect them from accidental damage. 
• Never force glass in or out of the frame. Use careful and precise movements to safely remove and install the panes. 
• Use window suckers to hold and move large glass panels.

Should you upgrade to double glazing?

If you’re coming from single glazed windows, and your room is costing a lot to maintain heat and you want better thermal and sound insulation then definitely, yes.

Double glazing a window offers better insulation and is designed to last longer. If not for the sake of affordability, double glazed windows will make a room warmer and quieter from the outside.

If you already have double glazed windows installed, then just consider maintenance when needed such as cleaning, if you have the budget, maybe upgrade to triple glazing in extremely cold conditions or if you’re next to a noisy highway. 

Ready to glaze?

Who would’ve guessed that there’s actually so much when it comes to windows? Glazing, more than it is on donuts, is an essential and necessary part of window manufacturing and functionality because it is what’s responsible for allowing windows to keep humidity and water out while letting the sun in. 

The reason why houses are able to hold changing internal temperatures and let you see outside is because of window glazing – as they provide insulation and climate control.

So, the next time you experience a draft despite having the windows closed, give them a quick look, they might only need a re-glaze.