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How To: Remove Glazing Putty

How To: Remove Glazing PuttyWhether it’s steel windows or wood windows, removing glazing putty is one of the more frustrating things to do in my opinion. How hard the work is depends on a lot of factors, like how old the putty is and what type putty was used. There are a few tricks to remove glazing putty without breaking the glass that I can show you.

Mainly, it comes down to being patient and careful. No matter which technique you use, remember that you are working with very thin glass that doesn’t require much force to break.

Always keep yourself safe when working around glass by wearing safety glasses and gloves. You never know when you may have unexpected breakage.

How To Prevent Broken Glass

Before we get into putty removal techniques I want to give you a couple good tips on how to protect that beautiful wavy glass. After all that’s what we’re after here right?

1. Clean Corners – Make sure you clean the corners free of all the putty you can before trying to remove the glass. This is one of the most fragile areas and it’s the easiest to forget a little chunk of putty. Clean everything out of the corners very well before trying removal of the glass.

2. Stray Glazing Points – There is almost always an extra glazing point that you’ll miss, and it often spells doom for your glass. Double check that you have removed ALL the glazing points and then check again because there is always that one hidden one lurking.

The Chisel & Scraper

I’ve tried probably more than a dozen different tools and techniques to remove glazing putty, but it often comes back to the old standard. It’s not sexy or exciting or new, but for removing anything from cement putty to caulk, a good chisel can work wonders. And it’s super cheap and portable!

Like in the picture above, I like to run the chisel along the joint of the putty and the glass first. It usually takes a few passes, and with each successive pass, you’ll dig a little further between the putty and the glass, breaking that seal. Don’t try to get it in one pass, or you will likely break the glass. Take your time and work it a little bit at a time.

Once you’ve got the putty and glass separated, then move to the joint between the putty and the wood. Be extra careful here to not gouge the wood. Other than breaking glass, this is the most common issue with using a sharp chisel on a soft wood sash. Again, go slow and work methodically. Eventually, the putty will begin chipping or peeling off in chunks.

After the chisel has done its work, I use a ProScraper to scrape the rabbets clean of any excess putty so that the glass will come out smoothly and not get caught up on any trouble areas.

Steam Heat

This is what I use in my shop to remove glazing putty. It’s fast, clean, and very effective. Not to mention, it keeps the dust down and that helps us work Lead Safe. You can use any standard clothes steamer and do spot work, or you can build a steam box (learn how here) pretty inexpensively. If you plan to do a lot of windows, a steam box is absolutely the way to go. For one or two windows, the chisel and scraper is the best.

After an hour in the steamer, the glazing putty is softened up and comes off much easier. It also comes with the added bonus of helping removing the paint in preparation for restoration. Check out my video of how steam glazing removal works.

Speedheater Infrared

It’s so much more than plain red, it’s…INFRAred! Seriously though, infrared heat is a great way to remove glazing putty. Like steam heat it helps to soften the putty and make it more pliable so that you can scrape it off with something as simple as a 5-in-1 or putty knife.

I place aluminum step flashing over the glass to protect it from the heat, otherwise you will end up with broken glass due to the intense heat. Just a few pieces that you can move from one section to another is enough to protect your glass.

When using any kind of infrared or even regular heat guns, be careful to keep moving. Don’t leave the heater in any one location for too long or you may end up burning the wood and paint. It doesn’t take much heat to soften the putty, so start with short 10-20 second bursts and gradually lengthen it out if necessary.

What About Cement Putty?

Cement putty is a real thing and it is more common on steel windows than wood windows, but it can show up anywhere. There are some putties that, once fully cured, are as hard as a rock and are completely immune to steam, infrared, chemicals, or anything else.

They are annoying and unpredictable as to where you will find them, but when you do, there is only one thing to do and that is to break out the chisel. It dulls chisels and is exactly like the name implies, hard as cement, but it will come out and it can be restored with new putty that won’t turn to stone. Good luck!

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23 thoughts on “How To: Remove Glazing Putty

  1. Right from the outset I am going to say this MIGHT NOT be a solution for thick layers of putty used to hold external windows.
    We are reglazing an internal sliding door of considerable age. The old pane was removed easily by removing 4 quad moldings nailed around the edge. Then we discovered that the pane had been bedded in some sort of brown putty about 1-2mm thick. We had to remove the putty so we could bed the new very rare glass pane in silicone as a shock absorber.
    This odd putty after 45 years was as hard as concrete and stuck to the wood like it was glued. Chipping at it took off wood with the putty, a heat gun helped a little but provided no real solution. Finally we tried 3 different paint strippers, each with a different active ingredient. I tried a little of each on a short section and 5 hours later we had a winner in our case a dichloromethane based paint stripper.
    I should mention that in 5 hours it had reduced the odd putty to something like chalk ie still a scraping job but at least now doable. Leaving over night was better and in some areas we had to apply stripper twice. Obviously this is not a quick solution, lots of time and patience and a small brush so as not to damage the finish on the door, but it left the wood in pristine condition for a job we had began to think near impossible.

  2. I discovered that using a heat gun that I use for stripping paint, along with a heat shield that I made with aluminum foil wrapped around a plastic paint edger, works very well and safely.

    It requires only 5 to 15 seconds of heating a section to soften some rock hard glazing, and the putty knife lifted it off simply after that. Saved a 120 year old 24″x32″ window pane. What a relief!

  3. Peelaway 8 paint removal system softens 90 year old glazing putty in two or three days. Then just carefully scrape it away with a razor blade, mask the glass, sand the residue off the rebate and the frame is ready for repairs, undercoating and new putty with glass intact and in-situ retained by the original points. This is the easiest way to do the job without the high risk of glass breakage from heat or mechanical impact methods.

  4. Another commenter already asked this but there was no response. Will New puddy bond to old puddy if it is too hard to remove?

    1. You can clean the excess putty residue off with a razor blade and glass cleaner if it has already dried. If it is fresh putty within 24 hrs then cleaning with whiting is the best route.

  5. Hi Scott.
    I’ve removed all the caulking from my 110 yo windows! However, somewhere along the way the window was recaulked and a bead of silicone was placed on the glass. I’m having a terrible time removing this seal.
    I’ve tried razor blades, wd40 and I’m not sure what to do. It’s not budging. Any ideas? Thanks!

    1. You can buy silicone removal liquid from most diy shops which with a couple of applications works relatively well.

  6. Hi Scott,
    I found removing old putty to be the most challenging part of re-glazing. Instead of completely re-glazing, would it work if I just patch the old putty? To do this, I would only scrape off loose old putty but spare those putty that still adhere well to the window, and then put new Sarco putty over these old remaining putty. Will the new putty bond well to the old putty?

  7. Can glazing putty be removed without taking out the window and/or glass? We have over 20 huge 3 pane windows in our church to repaint, but whoever did it last painted over the glazing putty. Help!

    1. Sue the old putty can be removed without removing the glass with some careful chiseling. The putty should be painted over with the paint lapping onto the glass about 1/16″ in order to seal the putty.

  8. I have used the box steamer. Did a casement window with 6 panes. The window did not fit when I re hung it. Is there any concern that the moisture will warp the wood/frame?? Thank you ahead of time.

    1. I’ve never had an issue with swelling or warping. The sash is back to normal moisture content after about 8-12 hours most times. Sometimes once the glass is out the sash can shift a bit and if the glass doesn’t go back into the right openings the sash may be slightly differently shaped.

  9. I have a couple of questions. In the video for the Silent Paint Remover they suggest applying BLO before stripping to loosen the putty and paint. Have you tried this? Also, how long should you allow the wood to dry after applying steam? I live here in Central Florida and moisture is my sworn enemy (as the hurricane bears down on us…).

    1. Karen, I’m in Central FL too! After 1 day the sash is dried out back to where it needs to be. The BLO helps a little bit, but I haven’t noticed a big difference.

  10. Nice post Scott! I also like to use a bench chisel to remove old glazing putty- with one modification. I take a standard 3/4″ bench chisel, drill a hole about 3/4″ up from the tip (using a carbide bit!), and mount and small 1/2″ OD router bit bearing on the flat face of the chisel. The bearing rides along the adjacent wood surface and allows me to precisely control my depth of cut. This helps prevent the chisel from slipping and gouging wood or cracking glass. Works like a charm on the windows in my 1931 storybook cottage.

    1. Hi Dane,
      Could you possibly explain this a bit further (the placement/attachment of the router bit bearing)? The router bit bearing is just a flat circle, isn’t it? I’m having a hard time imagining how you’re attaching it to the chisel and how it prevents gouging wood or cracking glass. I would love to try this – anything that makes this process a little less risky for wood and glass.

      Thank you!

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