Drafty windows drive up energy bills and make winter miserable. Reglazing your old windows seals out the cold, protects the wood frames, and restores that classic look. We show you exactly how to tackle this DIY project, from removing the old putty to getting a smooth, professional finish.
Key Takeaways
- Window glazing refers to the process of securing glass into a window frame using a putty compound or “glaze.”
- Reglazing involves removing old, cracked putty, priming the bare wood, and applying fresh compound to seal the glass.
- Fresh glazing improves home insulation, stops air leaks, and prevents moisture from rotting the window frames.
- Modern alternatives to traditional oil-based putty include silicone sealants and mitered wood moldings.
What Is Window Glazing?
Window glazing technically refers to the glass itself, but in the DIY world, it usually describes the putty used to secure that glass to the frame. Over time, this compound dries out, cracks, and falls away. We will walk you through replacing that old putty to ensure your home stays protected from wind and rain.
How to Glaze a Window
Older wood-framed windows rely on glazing putty to create a weather-tight seal. Modern windows often use vinyl or aluminum stops, but vintage homes need that traditional touch.
Gathering the right tools before you start makes this sticky job much easier.
For The Best Results
Remove the window sash (the moving part of the window) and clamp it onto a flat work table. You can reglaze vertically while the window is installed, but gravity makes it much harder to get a smooth line.
Essential Tools and Materials
- Heat gun with a nozzle shield.
- Stiff putty knife (chisel style).
- Glazing tool or flexible putty knife.
- Utility knife.
- Oil-based or shellac primer.
- Acrylic caulk (optional for bedding).
- Glazing points (metal triangles).
- Glazing compound (putty).
- Mineral spirits.
- Paintbrush.
- Replacement glass (if yours is broken).
Removing Old Window Putty
1. Soften and Scrape
Old putty turns into rock-hard cement over time. If it is cracked and loose, chip it away carefully with a stiff putty knife. If it refuses to budge, use a heat gun to soften the compound.
Hold the heat gun about two inches away and move it back and forth until the putty softens. Scrape it out immediately.
Protect Your Glass
Glass breaks easily under high heat. Use a metal heat shield attachment on your gun to direct heat only at the putty. If you do not have a shield, hold a broad drywall knife against the glass to deflect the hot air.
2. Prime the Bare Wood
Once the groove is clean, sand it lightly and wipe away the dust. Apply a coat of shellac primer, such as Rust-Oleum Bulls Eye Shellac, to the bare wood.
Do not skip this step. Dry wood will suck the oils right out of your new putty, causing it to dry out and crack prematurely. Shellac dries in minutes, so you can keep working.
Installing the Glass
3. Measure and Cut (If Needed)
If you are replacing broken glass, measure the opening width and height. Subtract 0.125 inches (1/8 inch) from both measurements. This gap allows the wood frame to expand and contract with the weather without shattering the glass.
Take these measurements to a hardware store to have the glass cut professionally, and grab a pack of glazing points while you are there.
4. Bed the Glass
Never place glass directly against bare wood. You need a “bed” of material to cushion it and create a seal.
You can lay a thin bead of latex caulk or a thin layer of putty in the frame rabbit (the L-shaped groove). Press the glass firmly into this bed until putty or caulk oozes out the back. Insert glazing points every eight inches to lock the glass in place.
Applying New Glazing Compound
Now comes the artistic part. Knead a handful of glazing compound in your hands like dough until it feels warm and pliable. If it is too stiff, it will drag and tear.
5. Pack the Frame
Take a generous chunk of putty and roll it into a thick rope. Press this rope firmly into the groove around the glass. Ensure you push hard enough to fill every void; air pockets will lead to failure later.
6. Smooth the Bevel
Dip your glazing tool or flexible knife into mineral spirits. Hold the knife at an angle and run it along the putty in a single, smooth stroke to create a neat bevel. The goal is to match the angle of the existing putty on other panes.
If the putty pulls or tears, add more mineral spirits to your knife. Clean the blade often to keep the line sharp.
7. Clean the Excess
The smoothing process usually pushes extra putty onto the glass. Let it sit for a moment, then use your knife to slice away the excess in a straight line. Be careful not to nick your fresh bevel.
Benefits of Spot Reglazing
You do not always need to strip the entire window. If only one section of putty is missing, you can perform spot repairs.
This saves time and reduces the risk of breaking old, fragile glass during removal. However, if the majority of the putty is cracked, a full reglaze is the only way to stop moisture from rotting your expensive wooden frames.
Window Glazing Alternatives
If traditional putty feels too difficult or time-consuming, you can use modern materials to secure your glass.
Silicone Sealants
Silicone adheres aggressively to glass and wood. It stays flexible and handles weather changes well. However, pure silicone cannot be painted, so it might ruin the look of a vintage home.
If you choose this route, look for a “paintable” silicone hybrid or high-quality exterior acrylic latex caulk. Just be aware that caulk sets very fast, so you must tool it immediately.
Wood Stops (Mitered Moldings)
For a cleaner look, skip the putty entirely and use wood. You can install 0.25-inch quarter-round molding or square stops to hold the glass in place.
Cut the wood strips to fit the frame with 45-degree mitered corners. Apply a thin bead of sealant to the glass, press the wood molding against it, and secure the wood with brad nails. This creates a permanent, professional finish that is easy to paint.
Caution
Use a pneumatic brad nailer rather than a hammer. One missed swing with a hammer will shatter your new glass instanty.
Tips for a Professional Finish
Reglazing is an art form that takes patience. Use these tips to get results that look like they were done by a pro.
Master Mineral Spirits
Mineral spirits are your best friend during this project. They lubricate the knife for a smooth glide and help clean greasy fingerprints off the glass. Keep a rag soaked in spirits nearby to wipe your blade after every few strokes.
Watch for Lead Paint
If your home was built before 1978, the paint on your windows likely contains lead. Scraping dry lead paint creates toxic dust. Always wear a HEPA-rated respirator mask, work over a plastic drop cloth, and keep children away from the work area.
Choose the Right Putty
Not all compounds are equal.
- Oil-based putty: Traditional, long-lasting, and weather-resistant. It takes days or weeks to cure before painting.
- Latex/Acrylic glazing: Dries in hours and cleans up with water. It is less durable outdoors but great for quick interior fixes.
FAQs
Can You Glaze Over Old Putty?
No, you cannot glaze over old, hard putty. New compound will not bond to the old, dried material. You must remove the old glazing down to the bare wood or the glass bed to ensure a waterproof seal.
Do You Glaze a Window From Inside or Outside?
It depends on the window design. Most traditional single-pane windows have the putty on the exterior side to shed rain. However, inspect your specific sash; whichever side has the removable stops or putty line is the side you work on.
How Long Does It Take to Glaze a Window?
A beginner can expect to spend 45 to 60 minutes reglazing a single window pane, including removal and cleanup. Once you get the hang of the technique, you can reduce this to about 15 to 20 minutes per pane.
How Much Does it Cost to Glaze a Window?
DIY reglazing is very cheap; a container of glazing compound costs around $15 to $20 and covers multiple windows. Hiring a professional to reglaze a window typically costs between $300 and $350 per window due to the labor-intensive nature of the work.
When Can I Paint New Window Glazing?
If using traditional oil-based putty, you must wait until it forms a skin, which can take 7 to 14 days depending on humidity. Latex-based compounds can usually be painted within 24 hours. Always check the manufacturer’s label for specific cure times.
Seal the Deal
Ignoring cracked glazing allows water to seep into your window frames, leading to rot and expensive repairs. Tackling this project now prepares your home for the seasons ahead. With a little patience and the right technique, your windows will look brand new and keep the weather where it belongs.
